Grassland management for Stone-curlew

Detailed studies of a small number of Stone-curlews, breeding in Breckland in the east of England, give some clues as to how to provide the right habitat mix for these big-eyed, nocturnal waders. Increasing structural diversity, by ploughing and/or harrowing areas of grassland, can create an attractive network of nesting and foraging sites for breeding and non-breeding adults.

In a 2021 paper in Animal Conservation, Rob Hawkes and colleagues from the University of East Anglia, RSPB and Natural England give us insights into the daily lives of Stone-curlews nesting in the dry grasslands of East Anglia. By fitting five individuals with GPS tags and following their movements they were able to establish which habitats are used at different stages of the breeding season.

The Stone-curlew is the only migratory member of the thick-knee family. England is at the north-western limit of a breeding range that stretches east to the steppes of Kazakhstan, with birds wintering in southern Europe, North Africa, the Arabian Peninsula and the Indian sub-continent. Most English birds spend the winter months in Spain, Portugal, Morocco or Algeria but a small number are known to cross the Sahara. Stone-curlews return to East Anglia in March and April.

Unmodified grassland in the Brecks of East Anglia provides limited feeding opportunities for Stone-curlews
Creating heterogeneity within areas of grassland by ploughing and/or harrowing patches

During the twentieth century, numbers of Stone-curlew across Europe fell significantly, as mechanized farming expanded. The East Anglian population had dropped to fewer than 100 pairs by 1985 and it took huge conservation efforts to increase this to 200 pairs. Breeding birds are now typically to be found in sparsely-vegetated ground, often in spring-sown crops, on dry heathland or in semi-natural grassland areas, including those used for military training. Preferred food items, such as earthworms, soil-surface invertebrates, slugs and snails, are easier to find in areas of bare and broken ground than in thick grass, so grazing is an important part of conservation action on heaths and in grassland areas.

Each of these square treatments covers a hectare

The UK’s migratory Stone-curlew population has received a huge amount of conservation support, on the back of detailed studies of the species’ breeding ecology (Green et al. 2000).  Tremendous efforts have been made to maximise chick production in farmland, with conservation staff and volunteers working with farmers to monitor breeding pairs, so that they can protect nests and chicks during crop-management operations. In the long term, however, such interventions are too labour-intensive to be sustainable. Can equivalent benefits accrue if more Stone-curlews nest successfully in semi-natural grassland, where the costs of conservation subsidies are lower than in intensively farmed arable cropland?

The study that is reported in the 2021 paper in Animal Conservation took place in an extensive area of semi-natural grassland (nearly 40 km2) that is surrounded by a mosaic of arable farmland. The aim was to understand whether ploughing or harrowing patches of grassland can provide suitable foraging areas, and which other habitats are important.    

Tracking Stone-curlews

GPS tag attached to the back of a Stone Curlew

Stone-curlews are predominantly nocturnal feeders so some form of remote tracking device was needed to understand their movements. GPS loggers were fitted to five adult Stone-curlews during the breeding season. Individuals were caught at night using small, beetle-baited, elastic-powered clap-nets or in the daytime using nest-traps. Each individual was fitted with a 5.2 g solar-powered nanoFix Geo PathTrack GPS tag and an external whip antenna. GPS data were downloaded to a remote base station through a radio connection. Tagged birds were visited at least once a week to establish whether they were still nesting, if they had chicks or had finished breeding.

Where did they go?

One, two and three hectare plots of disturbed ground had already been created within Breckland’s grassland and heathland areas, prior to this study, as described in the paper and discussed in the blog Curlews and foxes in East Anglia. It was already clear that these plots were favoured as nesting sites but does disturbed ground also provide additional feeding opportunities for adult birds – including pairs nesting nearby on arable fields?

Using a telescope to point the base station ‘reader’ at a bird wearing a GPS logger

Three male and two female Stone-curlews were tracked for more than nine weeks (67 to 102 days), yielding 510 GPS fixes during nesting and 1371 post-breeding. There were some fixes in the pre-nesting phase and also during the chick-rearing phase but too few to be considered for analysis. Analytical methods are detailed in the paper.

During the nesting period, what was presumed to be the off-duty bird of each pair was found within 1 km of the nest on 90% of fixes. The mean distance from the nest during daytime feeding was about 100 m but, at night, tagged birds travelled five times as far, on average. They travelled furthest when heading for pig-fields and manure heaps.

  • Relative to closed, undisturbed grassland, nesting Stone-curlews were two- to three-times as likely to forage on disturbed-grassland during night and day, but especially during the day.
  • Night and day, ‘sugar beet or maize’ fields were used more than unmodified-grassland but similar to disturbed-grassland.
  • Nocturnally, Stone-curlews were ten-times as likely to use ‘pig fields or manure heaps’, when compared to undisturbed grassland.
  • The furthest distance travelled was just over 4 km, which is further than previously thought.
Stone-curlews will fly a long way to feed in pig fields

In the post-breeding period, tagged birds travelled up to 13 km to forage, with 90% of nocturnal foraging locations found to be within 5 km of day-time roosting sites.

  • Tagged birds were approximately 15-times as likely to use either disturbed-grassland or arable fallows when compared to undisturbed grassland.
  • Use of the category ‘pig fields or manure heaps’ was nearly as strong (factor c. 10), in comparison to undisturbed grassland.
  • Open crops in the categories ‘sugar beet or maize’ and ‘vegetable or root crops’ were also used more than undisturbed-grassland (factor c. 2).

Conservation messages

In England, there has been a long-term focus on trying to maximise Stone-curlew productivity within arable farmland, especially in East Anglia but also in Wessex. As suggested earlier, this is expensive – foregone production requires high subsidies and interventions by conservation staff are time-consuming. A French study, written up in Ibis by Gaget et al., seriously questions the viability of Stone-curlew populations within intensively managed arable farmland, even with conservation support. Given these problems, should conservation efforts focus on supporting and building up grassland populations?

In a previous tracking study, thirty years previously, Green at al. found that short semi-natural grassland provided suitable foraging habitat for Stone-curlews. Much has changed in Breckland in the intervening period, with the collapse of the rabbit population and an increase in the amount of outdoor pig-rearing. As the short swards of rabbit-grazed grassland have disappeared, Stone-curlews seem to have increasingly taken advantage of alternative opportunities offered in pig fields.

Previous attempts to replicate the grazing efforts of rabbits have involved increasing livestock numbers but this study shows that physical ground-disturbance interventions immediately and effectively create alternative foraging habitat. The authors suggest that multiple areas of disturbed-ground, close to the edge of large grassland blocks, can provide a network of nesting and foraging habitats, whilst allowing access to a mixture of feeding opportunities in the surrounding arable farmland. Of course, nobody is suggesting that intensive outdoor pig-rearing is a positive addition to the habitat mix, as it involves nutrient run-off, ammonia leakage into fragile plant-rich heathland, and pelleted feed attracts corvids (which are known to predate eggs).

The effect of creating ploughed or harrowed plots is almost immediate, in terms of prey availability. In more detailed studies of the effectiveness of slightly different ground-disturbance options, the research team found a strong selection preference only one year after the treatments were first implemented. In the longer term, these areas may become increasingly important, if young birds recruit to the local population and seek out these features. The researchers suggest that a bespoke, ground-disturbance agri-environment option might open up new breeding opportunities within semi-natural grasslands that are currently dominated by tall, closed swords. 

In England, conservation of dry grasslands and heathlands has tended to focus on the preservation on charismatic plant communities, an approach that may have been too gentle and conservative for other taxa. Whilst this study demonstrates that adding pockets of disturbed ground appears to benefit Stone-curlews, previous studies, conducted by this research team, showed benefits for Woodlark (Hawkes et al. 2019), Eurasian Curlew (Zielonka et al. 2019, summarised in Curlews and foxes in East Anglia), and rare, scarce or threatened dry-grassland invertebrates (Hawkes et al. 2019). Similar disturbance techniques have been shown to potentially benefit other grassland-breeding waders, such as Mountain Plovers (Augustine & Skagen 2014) and Upland Sandpipers (Sandercock et al. 2015) in North America, and Sociable Lapwings in Kazakhstan (Kamp et al. 2009).

Paper

This is a summary of a 2021 paper in Animal Conservation:

Effects of experimental land management on habitat use by Eurasian Stone-curlews. Robert W Hawkes, Jennifer Smart, Andy Brown, Rhys E Green, Helen Jones & Paul M Dolman.

Each summer, farmers, volunteers and conservation staff work together to monitor and protect nesting Stone-curlews on farmland, grasslands and heaths in eastern and southern England. Thanks to all of these people, the number of pairs of Stone-curlew in England is holding steady, at over 300 pairs. Progress was reviewed at a conference in 2017, as you can read in this layman’s report and this technical report. More guidance for landowners can be found here.


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

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Oystercatcher Migration: the Dad Effect

What determines whether some birds migrate and others do not? This question is fundamental to understanding how migratory systems change over time but the causes of individual migratory behaviours have proved difficult to isolate.

Verónica Méndez and colleagues are studying Icelandic Oystercatchers, some of which remain in Iceland for the winter but most of which migrate across the Atlantic to Ireland, Britain and mainland Europe. In a 2021 paper in Scientific Reports they show that a chick’s migratory behaviour seems to align with the behaviour of its father but not its mother. What can explain this pattern?

The story so far

The Icelandic Oystercatcher study system has already featured in three WaderTales blogs. The first was Migratory decisions for Icelandic Oystercatchers. This focused upon the key questions that Verónica Méndez and colleagues from the universities of Iceland, East Anglia (UK) and Aveiro (Portugal) are trying to answer.

  • Why do some Oystercatchers migrate when others don’t?
  • Is it the same birds each year?
  • Do resident or migrant birds have an advantage when it comes to choosing a territory and raising chicks?
  • Do chicks follow the same migratory patterns as their parents?

When the first blog was written, in 2015, eight colour-ringed Oystercatchers had been seen in Ireland and the UK, and five had been seen wintering in Iceland. Fast forward to the next blog in 2018 – Mission impossible? Counting Iceland’s wintering Oystercatchers – where counts showed that over 11,000 Oystercatchers spend the winter in Iceland. Using colour-ring sightings of resident and migratory birds, the research team concluded that this total is about 30% of the whole Icelandic population. The other 70% fly south across the Atlantic each autumn, with no individuals yet observed to change what they do between years.

In the third blog – Which Icelandic Oystercatchers cross the Atlantic? – some patterns were starting to emerge.

  • Females and males are equally likely to migrate.
  • Size does not matter – small and big birds are equally likely to migrate
  • There are regional patterns across Iceland, with birds breeding in the west being most likely to be resident.
  • Birds do not pair up assortatively – residents don’t pair up with other residents before the migrants return, for instance.

Family ties

In most species of waders, parents protect their chicks and take them to suitable feeding areas but they do not actively feed them. Parental care in European Oystercatcher includes foraging for food and bringing it back to the chicks. This is why it is possible for Oystercatchers to nest on the roofs of buildings (Oystercatchers: from shingle beach to roof-top), where they are out of the reach of ground predators.

Focusing on chicks

To be able to understand the relationship between migratory behaviour in adults and their chicks, you need to be able to mark and then attempt to follow all of the members of a family. Adult Oystercatchers generally keep the same mates and nest in the same areas year after year, enabling the establishment of marked population of birds in different parts of Iceland. Between 2015 and 2018, a total of 615 incubating adults were caught. By following the outcomes of nesting attempts and then monitoring the growth of chicks, the research team also managed to individually mark 377 chicks.

Three colour-ringed chicks. Where will they go?

The success of the whole project relied heavily upon winter sightings of marked birds within Iceland and in Ireland, the UK and continental Europe. Through a network of volunteer observers reporting sightings of marked individuals across the wintering range, the migratory behaviours of 227 of the 615 colour-marked adults and 50 of the 377 colour-marked chicks had been identified at the time that this paper was written. In addition, it was possible to infer the migratory behaviour of 353 marked adults using measurement of isotope ratios (δ13C and δ15N) of feathers that were grown in the winter (as described here).

The analyses in the paper by Verónica Méndez and her colleagues are based upon 42 marked chicks of parents for which the migratory behaviour of both parents is either known or can be inferred from isotopic signatures. These chicks all fledged successfully and were seen during the winter period, either in Iceland or having crossed the Atlantic. In three cases, two chicks from the same broods are known to have behaved in the same way. More data have become available since the analyses, all confirming the same patterns.

Results

It is possible to imagine a scenario in which late or slow-growing Oystercatcher chicks might be more likely to stay in Iceland than their more mature counterparts – simply by developing too late to gain enough resources to cross the Atlantic. Analysis of hatch dates and growth parameters did not suggest the existence of such a link, as described in the paper.

This young Oystercatcher was spending its first winter on the coast of western Iceland

The interesting finding of this study is the link between the behaviour of parents and chicks. Data generated by observations of colour ringed individuals (adult and chicks) and from isotopes (adults) established 21 chick/parent associations.

  • Of the sixteen chicks raised by migrant mothers, eight migrated and eight remained in Iceland.
  • Of the five chicks raised by resident mothers, three migrated and two remained in Iceland.
  • All ten of the chicks raised by migrant fathers migrated from Iceland.
  • Of the eleven chicks raised by resident fathers, one migrated and ten remained in Iceland.
  • Seven chicks that fledged from pairs with one resident and one migrant parent adopted the migratory behaviour of the father.

This is pretty compelling evidence that chick migratory behaviour is associated with paternal (and not maternal) migratory behaviour!

What does this mean?

There is no evidence of genetic control of migratory destinations and both Oystercatcher parents care for chicks, so what mechanism could produce such strong paternal but not maternal effects?

The authors suggest that the migratory behaviour of individual oystercatchers may be linked to social interactions they experience during the post-fledging period. In shorebird species, such as Oystercatchers, mothers commonly depart before the chicks fledge, or at about the same time. Fathers often provide parental care for longer and this extended period of the parental bond may underlie the link between paternal and juvenile migratory behaviour in Icelandic Oystercatchers. Despite being able to fly and feed independently, juvenile Oystercatchers in Iceland have been seen begging for food several months after fledging, suggesting that some parents (most likely fathers) may care for youngsters much longer than in other species.

This Iceland-ringed Oysterctatcher was photographed in Guernsey in January 2021. It departs at the start of February each year.

Under this extended-care system, a chick that is being look after by a resident male may well become a resident, simply by following dad. As autumn arrives, the youngster can follow his parent when he moves to the coastal mudflats where resident Icelandic Oystercatchers spend the non-breeding season. Autumn turns to winter and the chick is destined to be a resident.

Is it possible to explain a similar link for migrants? As the breeding season comes to an end, migrant fathers leave their breeding areas and head south, across the Atlantic, leaving fledged youngsters to fend for themselves. Groups of youngsters gather together in flocks which also include adults that are feeding up in preparation for migration. Although not influenced by their own fathers, chicks may follow the cues of other migratory adults, thereby creating the patterns seen in this paper.

Most of the chicks included in these analyses were early-fledged birds, simply because earlier nesting attempts tend to be more successful. The research team were unable to detect any significant effect of fledging date on migratory behaviour but they do not rule out the possibility that late-fledging individuals lack the time or resources to undertake a migratory journey, irrespective of paternal behaviour.

The broader context

Migratory behaviour typically arises in seasonal environments, allowing individuals to exploit peaks of resource abundance in distinct locations across the world. Rapid shifts in the distribution and migration phenology of many migratory species present challenges to site-based conservation strategies. There is an urgent need to understand the processes that influence individual migratory behaviour, in order to attempt to predict species’ responses to environmental change.

The findings in this paper suggest that the social interactions experienced by individuals can directly influence the development of their migratory behaviour, and that the extent and timing of parental care may be key in shaping individual access to these social interactions. You can read the full paper here:

Paternal effects in the initiation of migratory behaviour in birds Méndez V., Gill, J.A., Þórisson, B., Vignisson, S.R., Gunnarsson, T.G. & Alves J.A.


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Winter conditions for Whimbrel

Up until relatively recently, it was hard to study the same population of migratory waders in both its breeding area and its wintering grounds. Ringed birds established links between different countries but to follow a group of individuals through a complete annual cycle was nearly impossible. Geolocators, and more recently satellite tracking, are starting to enable scientists to piece together whole stories.

Camilo Carneiro and colleagues from the University of Aveiro in Portugal (Dep. Biology & CESAM) and the University of Iceland (South Iceland Research Centre) have been tracking Whimbrel travelling between Iceland and Africa for nearly ten years, using geolocators. In the latest paper to come out of this research they investigated carry-over effects; do conditions experienced in wintering locations affect breeding success?

How might carry-over effects work?

The conditions experienced during one stage of a migrant’s annual cycle may affect their performance in subsequent stages. Perhaps the resources available at a wintering site might affect the timing of spring departure and whether an individual has to stop off to refuel? In turn, such individual differences may be apparent in individuals’ arrival dates in the breeding area, and the condition they are in might affect laying date, clutch size, egg weight, etc?

Icelandic Whimbrel spend the wintering season anywhere between south-west Europe and the tropical coastal areas of West African countries such as Benin and Togo. Despite this huge non-breeding range, individuals are highly philopatric, travelling between the same breeding area and the same restricted wintering site on an annual basis, perhaps for twenty or more years. A Whimbrel flying to the Bijagós Archipelago of Guinea-Bissau covers nearly 6000 km, in the autumn, whereas a bird that only travels to the Tejo (Tagus) Estuary of Portugal flies not much more than half as far (see map). The ‘winter’ conditions they experience are completely different; short temperate days in Portugal or tropical heat in the mangroves in Guinea Bissau.

Camilo and colleagues were able to study Whimbrel in different wintering locations, in order to understand the conditions that are experienced by breeding birds from these areas. They measured annual return rates for birds that had flown different distances and experienced different conditions in the non-breeding season. Do Tejo birds, spending the non-breeding season in the coldest part of the wintering range, have a lower apparent chance of survival? Do those that make it through a Portuguese winter return to Iceland earlier and thereby increase their chance of breeding successfully?

Life on the wintering grounds

Camilo Carneiro has studied wintering Whimbrel in three sites – the Tejo Estuary (Portugal), the Banc d’Arguin (Mauritania) and the Bijagós Archipelago (Guinea-Bissau). Birds in the three sites experience very different conditions between the start of September and the end of March, as discussed in the paper and illustrated in the table below.

Hundreds of observations of individual Whimbrel and flocks provided information on feeding rates, diet and foraging time. Comparable food items were collected from the mud/sand substrates and the energetic values were calculated in the laboratory. Together, these data enabled a calculation of energetic intake. The Net Energetic Intake Rate varied markedly. The figure for the Bijagós is 3.9 times that of the Tejo and 1.4 times that of the Banc d’Arguin.

Crabs provide a large part of a Whimbrel’s winter diet

Birds have a basic running cost – the Basal Metabolic Rate – which is related to the size of the individual and ambient conditions it experiences. Those wintering in areas where they experience periods of colder and windier weather lose more heat and hence need more energy. The BMR was calculated as 2.17, 2.29 and 2.51 Watts for individuals wintering in the Bijagós, Banc d’Arguin and Tejo, respectively, showing that there are higher ‘running costs’ in northern sites. Whimbrels in the Bijagós never incurred energetic costs above BMR, whereas those in the Banc d’Arguin and Tejo had additional energetic costs on 20.6% and 9.7% of the winter days, respectively.

The daily energetic balance differed hugely. Whimbrels in the Bijagós experiencing an average energetic surplus of about 700 kJ/day, followed by 420 kJ/day in Banc d’Arguin and just 11 kJ/day in the Tejo. It should be noted that these figures are based only on day-time feeding.

A colour-ringed bird hiding in a Bijagós flock

Returning to Iceland

The research team has shown that Whimbrel can either fly directly to Iceland or stop off and refuel. It is thought that between 80% and 90% of journeys include a stop-over, typically in Ireland or western Britain. Direct flight takes four or five days. (see summary of previous papers and blogs below).

Whimbrels arrive back in Iceland between the end of April and late May, quickly taking up territories unless there is snow cover. Regular visits to the main study area in the Southern Lowlands helped to ascertain which colour-ringed birds had returned when. Nests are found, and eggs are measured and ‘floated’, to estimate the laying date.

During incubation, attempts were made to catch marked individuals that were carrying leg-mounted geolocators. Adults trapped on the nest are measured, unringed birds are marked and three to five feathers are removed from the breast. These feathers will have been grown in the bird’s wintering area and carry an isotopic signature from that region.

Using stable isotope analyses of the breast feathers, ground-truthed by birds tracked using geolocators, Camilo managed to assign the winter location to 180 Whimbrels. 159 had flown from the tropical region (which includes Bijagós), while 20 had spent the winter in the arid region (which includes Banc d’Arguin) and one in the temperate region (Tejo). When linking the wintering region to breeding phenology and investment, the research team found that:  

  • There were no differences in the size of the birds returning from the tropical and arid regions.
  • There was no difference between the probabilities of a bird successfully returning from the tropical and arid regions.
  • The timing of nesting and the volume of the eggs that were laid by females was not different for birds from the tropical and arid regions.

Where to spend winter?

Only one marked bird definitely wintered in temperate southwest Europe, which is not surprising given that there are not large flocks of Whimbrel in the estuaries of this area. This bird was excluded from the analyses but we know that it will have travelled much less far than birds wintering in Africa and experienced winter conditions in which it could barely meet its daily energy requirements.

Individuals wintering in the arid region, including birds in the Banc d’Arguin, travelled a lot further than birds wintering in southwest Europe. These birds had an expected surplus of 420 kJ per day on an average day but strong winds meant that there were 20% of winter days in which conditions were sub-optimal.

Trying to find Whimbrel in a sandstorm in Banc d’Arguin

Individuals wintering in the Tropical group, including birds in the Bijagós, travelled 900 km further than the Arid group but found more predictable weather conditions, achieving an estimated spare energy capacity of 700 kJ per day, without days with energetic costs above BMR. The authors point out that this energy surplus will likely be needed during long periods of moult and to fuel spring migration.

The authors conclude that any costs associated with having to fly further to reach the tropical region are compensated for by benign conditions. This does not mean that an individual bird makes a choice between Tejo, Banc d’Arguin and Bijagós. Happenstance may determine where a juvenile ends up in its first winter and philopatry means that, if alive, it continues to spend subsequent winters in the same area. Presumably the risks incurred by flying further (to Bijagós) balance out the risks incurred by wintering in a less predictable environment.

Life in and amongst the mangroves of the Bijagós

Very few Whimbrel spend the winter on the Tejo, in Portugal, and calculations in the paper suggest that there is a high risk of not being able to find enough food. This would probably translate into high mortality and explain low numbers.

Carry-over Effects

Although no carry-over effects were found, the authors discuss ways in which they may show up in other traits. There is an interesting discussion as to how carry-over effects might link experiences in the wintering grounds to breeding output in the next breeding season. Amongst other things, the authors suggest that differences among individuals using different wintering sites may only become evident if assessed over several years. We know that conditions are less benign in Banc d’Arguin, for instance. Perhaps there are years when conditions are bad enough for long enough to influence survival or body condition in spring. In such a year, there could be impacts on the ability to migrate, an increased likelihood of dying during migration or delayed breeding. It is possible that longer-term studies will pick up differences in return rates and/or breeding success for birds wintering in different areas? We shall see.

Paper

Linking range-wide energetic trade-offs to breeding performance in a long-distance migrant Camilo Carneiro, Tómas G. Gunnarsson, Verónica Méndez, Amadeu M.V.M. Soares & José A. Alves

Previous research on Icelandic Whimbrel

This Whimbrel, photographed in Bijagós is wearing colour-rings that were fitted in Iceland

Whimbrels on the move summarised the movements of Icelandic birds, based on reports of ringed and colour-ringed individuals. In the paper upon which the blog was based (Gunnarsson & Guðmundsson) there was a strong suggestion that birds only stop off in Britain & Ireland on the way north. Geolocator-based research by Alves et al showed that at least some birds were flying straight from Iceland to West Africa and that these sea-crossings could be very rapid.

Migrations to and from Africa were investigated further in a paper by Camilo Carneiro et al that was summarised in Iceland to Africa, non-stop. More recently, papers by the same team have shown that the most consistent point of the annual migration story is departure from Africa and discussed the links between weather and phenology. These two papers have appeared as the WaderTales blogs – Whimbrel: time to leave and A Rhapsody of Whimbrel.

Further reading

The following WaderTales blogs all consider how migratory behaviour might affect breeding season success, although without the direct measurements for individuals that have been carried out in the Whimbrel study.

Overtaking on migration shows that potential costs of migrating further can be overcome by undertaking early spring migration to staging sites that are closer to breeding areas.

Travel advice for Sanderling summarises research to understand the pros and cons of spending the non-breeding season in widely different locations.

Gap years for sandpipers is based upon a Peruvian Semipalmated Sandpiper paper that investigates the survival advantage of not migrating north to breed in a particular year.


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Following Sociable Lapwings

Understanding the migration routes of threatened migratory species is key to supporting declining populations.

Targeted help for the critically endangered Sociable Lapwing has come another step closer, thanks to the publication of a paper by Paul Donald and colleagues in the Journal of Ornithology.  In it, they describe how satellite tracking, colour-ringing, studies of historical records and flock counts have combined to give a much clearer picture of the main sites used by Sociable Lapwings during migration and in the winter. In addition, the research team’s work has produced a more robust estimate of the world population of the species. Given the threats that Sociable Lapwings face when they are away from their breeding sites – particularly from hunting – this is all crucial information for their conservation.

The Sociable Lapwing

Nesting close to a village

Sociable Lapwings once bred from Ukraine through to western China. There still may be a small population in southern Russia but the breeding range is now almost entirely restricted to the steppes of central and northern Kazakhstan (Sheldon et al 2012). For centuries, Sociable Lapwings have relied upon grazing by herds of Saiga Antelopes, which created open areas in which to nest. As natural grazing systems have broken down, Sociable Lapwings have become increasingly restricted to grazed land around villages (Kamp et al. 2009). Given that current productivity levels appear sufficient to maintain this small population in a viable state, low adult survival is thought to be the most likely driver of recent population declines (Sheldon et al. 2013).

Prior to this study, little was known about the wintering areas used by Sociable Lapwings. There had been some reports of flocks in eastern Africa but most information from countries such as Sudan was several decades out of date. Further east, sightings in Pakistan and India accounted for only small numbers of the known population. Did birds travel straight from breeding areas to winter sites or were there key stop-over sites that were missing from the map? Did birds in the western part of the breeding range head southwest to East Africa, with those in the east heading south to Pakistan and India? It was time to track some birds!

Distribution map from BirdLife International data zone

Detective work

Colour-ringed individual

Paul Donald and colleagues undertook a long-term study of the movements of Sociable Lapwings, using satellite tagging, colour-ringing, targeted field surveys and a database of historical and recent sightings. The collation of this database involved a huge amount of painstaking work, with researchers checking museum collections, searching through unpublished literature, liaising with local birdwatching organisations and looking for bird lists and images, via the Internet.

Studies of breeding birds were mainly focused upon an area around Korgalzhyn, in central Kazakhstan where, between 2004 and 2015, 150 adult Sociable Lapwings and 1473 chicks were colour-ringed. The main aim was to estimate survival rates but some of these marked individuals provided valuable data when seen during visits to potential wintering and passage sites. Most of this fieldwork outside of the breeding season was undertaken by local conservationists and ornithologists, with their efforts being coordinated by the BirdLife International Social Lapwing Project.

Releasing a satellite-tagged bird

Detailed information on movement patterns was collected with the assistance of 29 satellite-tracked adult birds, caught in the breeding grounds between 2007 and 2015. Most were tagged near Korgalzhyn, in central Kazakhstan but five were tagged in an area about 800 km further east. Of these 29 birds, 21 were female. Technical developments by Microwave Telemetry Inc. meant that early 9 g solar-powered tags could be replaced by 5 g tags in later years.

Tracked birds

The paper by Donald et al contains detailed information about the movements of individual birds and how they were tracked. Anyone contemplating a similar study may want to read about how data were filtered and ‘clusters’ and ‘transit points’ were defined.

Early (larger) tags did not produce as much information as later (smaller) tags. The fact that one of the early-tagged birds was seen back on the breeding grounds without its harness and tag suggests that harness failures may have been an issue early on. 16 of the 29 tags provided data that enabled the research team to plot 27 complete autumn migration journeys and 13 complete spring journeys. Some birds were tracked for longer periods, producing data for two or more autumn (7 birds) and spring (3 birds) migrations. Birds followed for more than one year repeated almost exactly the same autumn and spring journeys.

Note the short vegetation

The tracked birds set off on one of two routes at the end of the breeding season, either heading west and south to northeast Africa and the Arabian Peninsula (the western route) or due south to Pakistan and India (the eastern route):

  • Seventeen birds used the longer western route, west across Kazakhstan, across or around the western Caspian Sea, then south through the Caucasus and the Levant, before reaching wintering areas in Saudi Arabia and eastern Sudan (map below).
  • Seven birds set off on the shorter eastern route, due south to Turkmenistan and Uzbekistan, then over or around the mountains of northern Afghanistan to wintering areas in Pakistan and north-western India.
  • Migration direction was ascertained for 22 birds from the central Kazakhstan group: 16 birds took the westerly route and 6 used the eastern route. Only two of the birds that were marked further east produced usable tracks, with one bird following the eastern route and one following the western route.
  • Birds using the eastern route travelled an average of 2839 km, with birds on the western route travelling 5199 km – nearly twice as far. Birds on both flyways departed their breeding grounds and arrived on their wintering ground at around the same time. Key stop-over areas were identified (see paper).
This tagged bird was photographed in a flock in Pakistan
  • In autumn, birds on the eastern route stopped only once, at Tallymarzhan (on the border of Turkmenistan and Uzbekistan), remaining in the area for between 29 and 48 days. Western birds stopped more often and generally for much shorter periods.
  • Central Azerbaijan and northern Afghanistan seem to be important spring staging sites for birds on the western and eastern routes, respectively, but these sites have yet to be surveyed.
  • The timing, direction and use of stopover areas of birds tracked in more than one year were highly consistent but there was much variation between individuals.

Only eight of the Sociable Lapwings colour-ringed as chicks on the breeding grounds in central Kazakhstan were subsequently seen outside Kazakhstan: five at the Kuma-Manych Depression in Stavropol (on the western route) and three at Tallymarzhan in Uzbekistan (eastern).

Three recently-fledged youngsters

Chicks and adults gather in mixed flocks prior to migration and it is thought that they migrate together. Perhaps circumstances and the adult birds with which young birds happen to associate determine the direction of the first migration south. If it is still alive, why should a young bird migrate in a different direction in a subsequent year?

Adults used up to three different areas during the course of a winter and, as far as could be determined from the small number of multi-year tracks, did the same thing in subsequent years. An analysis of the sites used by wintering birds emphasised the importance of arable habitats – most stopover sites are in areas that have been under cultivation for over 2000 years.

There was little evidence of strong breeding site fidelity, with adult birds moving up to 300 km from the site of tagging in the next year. For a species that may need to search for nesting sites in recently-grazed or burnt-off grassland, within a relatively homogeneous steppe habitat, it is perhaps unsurprising that there appears to be less of a tendency for birds to be site-faithful than seen in many other species of wader.

Finding the flocks

The research team found that their database of historical and recent records of flocks of migrating and wintering Sociable Lapwing identified the same two major migration routes that appeared from traces of tracked birds. There is a strong suggestion that there is a third, central route that takes birds to Oman, parts of eastern Saudi Arabia and to sites around the Persian Gulf and the Gulf of Oman. None of the 29 tagged birds happened to end up in these areas.

Counts on both sides of the border between Uzbekistan-Turkmenistan, in the autumn of 2015, suggested that between 6000 and 8000 Sociable Lapwings may use this area when migrating along the eastern route. Using information on the proportion of tagged birds that visited this area, and for how long, the research team estimate that the global population of Sociable Lapwings is about 24,000 individuals, although the 95% confidence interval is broad (13,700 to 55,560 birds).  The estimate is the most robust so far and the methodology can be repeated in the future, in order to monitor population change.

The bigger picture

In Palaearctic species with intercontinental flyways to both Africa and Asia, individuals breeding in the western part of the range usually take the western flyway and those in the eastern part of the breeding range migrate along an eastern flyway, with a clear migratory divide within the breeding range. This is the case for species as diverse as waders, bustards and bee-eaters. Discovering that Sociable Lapwings are not so similarly constrained was a surprise, with the route used being independent of the longitude of the tagging site.

Post-breeding moulting flock in central Kazakhstan

During migration and on the wintering grounds, Sociable Lapwings are strongly associated with areas of agriculture, particularly along rivers. Only in northern Syria and and Tallymarzhan were birds found in more natural steppe grasslands. Birds are now using irrigated areas of the Arabian Peninsula, where agricultural land has been created in former deserts. It appears that new generations of Sociable Lapwings, taking advantage of these novel opportunities, now undertake shorter migratory journeys and have perhaps established new pathways. This form of Generational Change is the subject of a WaderTales blog about Black-tailed Godwits.

Sociable Lapwings are widely dispersed over huge and often inaccessible areas on both the breeding and wintering grounds. Their concentration in a small number of predictable staging areas, during migration, offers the best opportunity to gather information on population trends. Birds using the western route appear to have more available options than birds in the east, making numbers harder to monitor.

Birds using the western route, particularly in Syria and Iraq, are targeted by hunters in the autumn and there is no protection for any of the stopover sites identified in this study. The authors suggest that it is particularly important to know more about spring staging areas in Azerbaijan, as this is a focal area for returning birds using the western route and potentially an area in which hunting takes a significant toll. Birds using the eastern route appear not to be hunted – or at least not in the same sort of numbers as in the west. Sociable Lapwings that use the less well-understood central route and that winter in the Arabian Peninsula may be vulnerable, as they share irrigated fields with species that are popular with hunters.

To learn more

The authors, and everyone else who has contributed to decades of Sociable Lapwing research, are to be commended for the work they have done. Now that key sites have been identified, it is to be hoped that there is political will to provide protection for this critically endangered species. Actions will need to include site designation, local involvement in conservation action and concerted efforts to curb illegal hunting.

Part of a flock of pre-migratory birds in central Kazakhstan (409 birds were counted)

The paper upon which this blog is based is:

Migration strategy, site fidelity and population size of the globally threatened Sociable Lapwing Paul F. Donald, Johannes Kamp,Rhys E. Green, Ruslan Urazaliyev, Maxim Koshkin & Robert D. Sheldon. Journal of Ornithology.

Other WaderTales blogs about tracking projects that help to identify migratory hot-spots used by threatened waders include:

Spoon-billed Sandpipers: Track and Trace (finding wintering and passage sites)

Black-tailed Godwits are on their way home (Tagus Estuary airport plan)

Teenage Waders (Hudsonian Godwits in the Pampa wetlands of Argentina)


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Gap years for sandpipers

Will this Semipalmated Sandpiper fly north to breed?

With the approach of spring in the Northern Hemisphere, waders (shorebirds) that have spent the previous few months on the shores of Africa, the Americas, Asia, Australasia, Europe and oceanic islands need to decide whether to fly north. Those that depart leave behind flocks of young birds, together with adults that ‘choose’ not to migrate north and attempt to breed. In a paper in Movement Ecology, Eveling Tavera and colleagues investigate how the decisions made by individual Semipalmated Sandpipers that spend the non-breeding season in Paracas (Peru) are likely to affect their chances of survival.

Semipalmated Sandpipers

The Semipalmated Sandpiper is one of the smallest of the world’s waders. The species is designated as near-threatened by BirdLife International and IUCN, despite its large breeding range. In their assessment, they draw attention to declining numbers, potentially linked to reduced food supplies in staging areas and to changes to arctic breeding habitat. Hunting pressure in some parts of the wintering range (especially the eastern seaboard of South America and in the Caribbean) may particularly affect Semipalmated Sandpipers that breed in eastern Canada.

Back in the 1970s, when I spent three summers in James Bay (northern Canada), I remember catching skinny juvenile Semipalmated Sandpipers that weighed under 20 g, which is way smaller than a House Sparrow (24.2 g – 30.7 g: BTO BirdFacts). We also caught fat, 40 g  adults that were about to leave and head to countries such as Suriname in South America, perhaps stopping off in the Bay of Fundy on their way south. In just a few months, it would be time to fly north again and I guess we assumed that any bird that was alive would at least try to make the return journey. After all, these are small shorebirds and most small shorebirds breed in their first year.

The distribution of Semipalmated Sandpipers during the non-breeding season covers a broad range of latitudes, from about 25°N (southern Florida) to 23°S (northern Chile and southern Brazil). Some of the birds flying to Arctic Canada, Alaska and Northeast Russia are travelling a lot further than others. A bird setting out on a return journey to northern Quebec from Peru will need to find more resources to fuel its journey than one flying from the Caribbean. The additional fattening requirement could potentially affect the ability of individuals to make the return migration.

Shorebird Survival

Graph from Méndez et al in Ibis

In their global review of annual survival rates of shorebirds, Verónica Méndez and colleagues were able to include 56 species from around the globe. Unsurprisingly, small waders tend not to live as long as larger species. Combining the various studies of Semipalmated Sandpiper, they estimated an annual survival rate for adults of 0.61 (see Measuring shorebird survival). This means that, on average, there’s a 39% chance of an individual dying between one breeding season and the next.

We know that waders don’t always breed every year, as discussed in Teenage Waders. Small waders have lower life expectancy than large waders (Waders are long-lived birds) so missing out on a breeding season makes much more of a difference to a small sandpiper than to a Knot (estimated survival rate 0.8 or 20% chance of dying within the next twelve months) or an Oystercatcher (0.89; 11%).

As Tavera et al point out in the introduction to their paper, although most small shorebirds attempt to breed in their first year of life they may have lower breeding success than older individuals. In Semipalmated Sandpipers, young birds start nesting later in the spring, lay smaller and fewer eggs, and produce fewer chicks (references in paper). When comparing potential reproductive output, a bird that does not migrate north in its first year is probably missing out less than an adult that ‘takes a year off’.

Breeding habitat in Alaska – a long way from Peru

Semipalmated Sandpipers in Peru

The results presented in the Tavera et al Movement Ecology paper come from a long-term Semipalmated Sandpiper colour-ringing study in the Paracas National Reserve, 250 km south of Lima, in Peru. Over a period of five years, 1963 birds were caught in mist nets and individually marked, producing 3229 resightings. Only eight of the marked birds has been seen during the nesting season, all in Alaska and western Canada. This paper builds on a previous paper: Effects of migration distance on life history strategies of Western and Semipalmated sandpipers in Perú.

The key findings in the study are:

  • 28% of first-year Semipalmated Sandpipers remain at Paracas, instead of heading north
  • 19% of adults remain in Paracas instead of migrating.
  • The apparent annual survival rate of first-years that head north is 0.555, compared to 0.671 for first-years that stay at Paracas.
  • For adults, apparent annual survival rate of those that migrate is 0.614, compared to 0.808 for those that stay.

The fact that 28% of youngsters in this particular population of Semipalmated Sandpipers don’t migrate north in the first year was unexpected, given what had been learnt from previous studies of the species, but the fact that one in five adults ‘choose’ not to breed in any year is probably more surprising. In a species with a declining population, these missed opportunities to boost the population appear concerning.

Short and long bills

Measuring bill length

Several thousand Semipalmated Sandpipers spend the non-breeding period at Paracas, including individuals with long bills (which are thought to fly there from eastern Arctic breeding populations, about 8,000 km away) and short bills (likely from western Arctic breeding populations, up to 11,000 km distant). There is more about these morphometric differences in this paper by Cheri Gratto-Trevor et al in Waterbirds.

It is not possible to assign individual Semipalmated Sandpipers to a particular population, especially as there are also sex-based differences in bill length, and gender could not be determined in the hand. However, there is a trend for longer-billed birds to be from the east. The eight colour-marked birds from Paracas that have been seen in the western part of the breeding range were all short-billed or intermediate-billed birds.

  • Larger-billed juveniles appear more likely to migrate than smaller-billed juveniles, suggesting that Semipalmated Sandpipers that have travelled less far are more likely to breed in the first year.
  • Resightings of flagged birds suggest that the survival of first-year birds that fly to the Arctic in their first spring is markedly lower in small-billed birds than in long-billed birds.

The cost of migration seems particularly high in small-billed, first-year Semipalmated Sandpipers. These birds tend to be longer-distance migrants, from the western end of the breeding range.

Modelling the costs and advantages of migration

Eveling Tavera and her colleagues have found that survival is higher for Semipalmated Sandpipers that stay in Paracas than for migrants. During the period April to September, the apparent survival rate for first-year birds and adult birds is much higher for birds that do not migrate.  The survival advantage acquired by non-migrants is significantly greater for adults (0.215) than for yearlings (0.140).

Clutch of Semipalmated Sandpiper eggs

By failing to migrate, individual Semipalmated Sandpipers miss out on a breeding opportunity. Does a bird that lives longer but does not breed in every potential year produce more youngsters than a bird that lives a little less long but breeds every year? In an appendix to the paper, the research team calculate whether the survival advantage for birds that stay in Paracas is high enough, in fitness terms, to compensate for the loss of potential youngsters. They used values for annual survival, mean clutch size and hatching success from studies by Weisser et al and Gratto et al, for adults and first-year birds, to produce figures for Lifetime Reproductive Success (LRS). The predicted survival advantage of non-migrating adults (0.240) is higher than that of first-years (0.134) because they forego a larger average potential reproductive output than do inexperienced birds.

Using these calculations:

Teamwork: birds are mist-netted at night
  • On average, a first-year migrant will have the same LRS as a bird that does not migrate if its survival in the first year is no more than 0.134 lower. This is close to the measured value of 0.140 for the Paracas birds.
  • On average, an adult migrant will have the same LRS as a bird that does not migrate if its survival in that year of life is no more than 0.240 lower. This is close to the measured value of 0.215 for the Paracas birds.

Based on the modelling of LRS and survival rates, the team conclude that ‘juvenile and adult birds staying at Paracas compensate for the loss of a breeding opportunity with higher survivorship than migrant birds’.

Different non-breeding populations

Tiny bill of an Alaskan Semipalmated Sandpiper

The Semipalmated Sandpipers that breed across North America and the far eastern tip of Russia travel to a wide range of destinations in the autumn, with birds mixing in the non-breeding season. The Paracas site is a long way from the species’ breeding grounds and the results may suggest that migration is constrained by distance. However, there could be other processes at play, especially if food supplies are limited at the time when individuals need to fatten up for migration. Jeroen Reneerkens et al showed that Greenlandic Sanderling that spend the winter near the equator (Mauritania & Ghana) had lower apparent survival rates than birds that travelled much further south (Pretoria). They were also less likely to breed in their first year than birds spending the breeding season in other locations, and arrived on their breeding territories late in the season. Migration distance is not always a problem, it transpires, as long as there are refuelling possibilities on the way north, as described in Travel advice for Sanderling. This is also discussed in Overtaking on Migration, a Black-tailed Godwit blog based upon a paper by Alves et al.

Conservation importance

Much of the statutory protection for migrant waders is based upon sites used in the non-breeding season. Eveling Tavera has shown that Paracas is important for the whole year. Are there other sites that hold 20% or more of their flocks of Semipalmated Sandpipers for the whole year? What are the conservation implications for this species, which is already designated as ‘near-threatened’? Are we doing enough to look after pre-breeding (and non-breeding) flocks? This issue is discussed further in Teenage Waders, built around a Hudsonian Godwit paper by Juan Navedo & Jorge Ruiz.

In conclusion

An individual Semipalmated Sandpiper does not, of course, have the experience or capacity to enable calculation of differential survival rates. The decision to migrate north will be based upon circumstances and the bird’s condition. Effectively, it is trading off the fitness benefit of higher survival against the fitness cost of a foregone breeding opportunity – but it does not know that that is what it is doing. What is interesting, in this study, is that the cost-benefit analysis so closely matches what is found using field data from this particular site. The survival rates and percentage of non-breeding Semipalmated Sandpipers in Suriname or at another site in Peru may well be completely different but could still balance out. There is so much more to learn about shorebird migration.

Oversummering juvenile and adult Semipalmated sandpipers in Perú gain enough survival to compensate for foregone breeding opportunity Eveling A. Tavera, Glenn E. Stauffer , David B. Lank and Ronald C. Ydenberg. Movement Ecology 8,42. https://doi.org/10.1186/s40462-020-00226-6


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Spoon-billed Sandpipers: Track and Trace

The cutest wader in the world has to be the ‘critically endangered’ Spoon-billed Sandpiper, a tiny wader with an ice-cream spoon for a bill. An ever-reducing number of pairs breed in the coastal tundra of north-east Russia. They migrate to south-east Asia, spending the winter months anywhere between China and Bangladesh.

During autumn there are sightings of moulting Spoon-billed Sandpipers around the mudflats of the Yellow Sea (People’s Republic of China, Democratic People’s Republic of Korea (DPRK) and Republic of Korea). Where else do Spoon-billed Sandpipers go? A new paper shows that it is possible to trace potentially important missing sites by tracking individuals.

Away from their breeding areas, Spoon-billed Sandpipers are threatened by:

  • Loss of non-breeding habitats, especially intertidal mudflats, because of land-claim projects to create harbours, industry zones, wind and solar power generation farms, aquaculture ponds and rice-fields.
  • The spread of invasive Spartina species (cordgrass) across mudflats in some coastal areas of China, the Republic of Korea and Japan is reducing the available feeding area.
  • Local hunting pressure, for personal consumption and local trade.
  • Accidental losses of birds tangled in permanently set fishing nets.

There is more about these issues and efforts to reduce problems being faced by waders on the East Asian-Australasian Flyway on the Saving the Spoon-billed Sandpiper website.

Better information on the location and timing of use of stopover and wintering sites is essential if conservation measures to prevent hunting and further losses of intertidal habitat are to be applied across the species’ range. In a 2020 paper in Wader Study, Prof Qing Chang and colleagues describe in detail the post-breeding migration of adult Spoon-billed Sandpipers. For the first time, they are able to report on the timing of the migration, the duration of stay at stop-over sites, and the distances travelled between stop-overs.

Six Spoon-billed Sandpipers were caught in Chukotka

The research team captured 13 adult Spoon-billed Sandpipers and fitted each bird with a solar-powered transmitter that reports the bird’s locations, via satellites. Six were caught on their nests in Chukotka and seven were netted at Tiaozini in Jiangsu Province, near Shanghai in China. The paper contains full information on the tags, which were glue-mounted to the back of the birds, and details of the data collected and the algorithms used to interpret groupings of locations. This will be of help to anyone considering using these devices.

Why use Satellite transmitters?

Information from colour-ringing and counting has produced fascinating information about Spoon-billed Sandpipers. We now know more about the breeding, migration and wintering locations of the total population, estimated at just 660** individuals in 2014, than we did in 2010, when the serious plight of the species became more widely apparent (Clark et al). There has been international support for conservation action in non-breeding hot-spots in Myanmar, Bangladesh and China, where waders are benefiting from measures designed to reduce hunting pressure and maintain feeding habitat.

** The population total has been updated since this blog was produced. Although numbers have continued to decline, the new estimate is between 569 and 978 (details at end of this blog and in this paper).

Counting waders in the Gulf of Mottomar in Myanmar

The amount of information that can be obtained from counts and colour-ring sightings is limited by knowledge of where to look for birds. There are still big questions to ask. Where do birds colour-ringed in Russia, but not yet seen, spend the winter, where are the breeding grounds for birds ringed in the winter and then not seen in the summer, and what happens to birds in the weeks when they are on migration? Geolocators or satellite transmitters might provide some answers.

Geolocators are great, but information can only be downloaded from these devices by recapturing tagged birds and there is poor precision of reports received during the equinox periods (late March and late September), when daylength doesn’t change with latitude and many waders are on the move. Additionally, given the tiny size of the population and the mobility of breeding birds, recapturing birds to remove geolocators is unlikely to be as easy as it has been for many other wader species. Finally, as has been discussed in a previous WaderTales blog, geolocators can have unanticipated negative consequences for small calidrid sandpipers.

Health & Safety

Every Spoon-billed Sandpiper is precious, so safety is of paramount importance in tagging studies. Prior to deployment on Spoon-billed Sandpipers, tags of the same weight and dimensions were trialled on ‘surrogate’ birds – a small flock of twelve captive-reared Dunlin. The health of these birds was monitored in an aviary and birds seemed to behave normally. Would the same be true for similarly-sized Spoon-billed Sandpipers that migrate thousands of kilometres? Imagine the relief when the first tagged wild bird took off a few days after tagging and started to reveal unique insights into the species’ migration!

From Russia with tags

The six adults captured on the nest and tagged in subarctic Chukotka, Russia, left in July and moved west and south through Kamchatka in July and early August. This was followed by long flights (>1,000 km) across the Sea of Okhotsk to Sakhalin Island. By this stage, only four of the tags were still functioning but these birds provided some fascinating information:

  • All four birds used the same area (Tyk Bay) on the western side of Sakhalin Island. They stayed for long periods and all flew long distances when they left – which means that this site and the resources it provides are really important!
  • The next leg of the journey took the birds further south to sites within Russia and to the Democratic People’s Republic of Korea. All four ended up in DPRK.
  • Two birds stayed long enough to moult close to the Demilitarised Zone in the DPRK but the other two moved on and spent a month moulting at two different sites in Jiangsu Province, China.
  • By this point, in the late autumn, it is believed that all four birds had moulted. Given the method of tag attachment, it was thought that birds would drop their tags during moult, but one bird (L07) continued to transmit data.
  • The four individuals that were tracked between the breeding area and their presumed moulting sites stopped for 2 days or more at between 3 and 7 sites.

Post-moult migration

Seven birds were tagged in Tiaozini in Jiangsu Province. With L07 still transmitting, that meant that there were eight birds to track during the next stage of the migration season. Would they be able to trace missing sites that could potentially be protected.

  • All eight of these birds moved west and south in October or early November.
  • Three birds moved to separate sites in southern China, where they remained until their tags ceased to provide data.
  • Five birds visited stopover sites in China before moving on to their wintering areas in Vietnam, Myanmar, Sumatra and Bangladesh. Sumatra is outside the previously-known wintering range.
  • One of the birds that flew to Bangladesh stopped in Vietnam and Myanmar, while the other one stopped in the Gulf of Thailand. It then overflew Malaysia, Myanmar and the Bay of Bengal before transmissions ceased just before arrival in Bangladesh.
  • The eight individuals that were tracked between moulting and wintering grounds trace out a vast coastline (figure) – illustrating the conservation challenges of trying to save the Spoon-billed Sandpiper. Only two of the birds finished up at well-known sites that are covered regularly by winter counts.

Identifying sites of conservation importance

With only thirteen tagged birds providing four links between breeding and moulting areas and eight links between moulting and wintering areas, the research team have greatly increased our understanding of how it might be possible to protect Spoon-billed Sandpipers. As the authors point out in their Discussion, however, the “list of stopover sites is not comprehensive because of the small number of birds tagged and the duration of stay criterion we used”. Seventeen sites were visited by only one bird and other sites where Spoon-billed Sandpipers are regularly seen were not visited by any of the tagged birds. This suggests that there are probably other important sites that are yet to be traced. The authors suggest some of the limitations created by sampling. The key findings are:

  • During the post-breeding migration, several sites appeared to be of special importance. Seven stop-over sites were used for long periods or were used by birds immediately before long flights (or both).
  • Tyk Bay (Sakhalin, Russia) and Ryongmae Mudflat (DPRK) were used as stopovers by all the tagged birds that passed beyond these sites. Neither site was previously thought to be important for Spoon-billed Sandpipers.
  • The post-breeding moult period is an energetically expensive stage of a wader’s annual cycle. For Spoon-billed Sandpipers, Ryongmae Mudflat (DPRK), Tiaozini (China) and Yangkou (China) are of special importance in this regard (Green et al. 2018, Chang et al. 2019, Yang et al. 2020).
  • Most of the sites in which tagged birds spent the winter months had not previously been visited by count teams. Subsequent visits to some of these previously unknown sites in China added counts of 77 birds.

Once tags had fallen off, birds could still be located by their leg-flags if they were seen by teams of observers who visited known moulting, stop-over and wintering locations. Seven of the birds that carried transmitters have been seen in subsequent years at similar times and places. This suggests that birds are site-faithful between years, implying that a site that is identified to be of importance is really important – birds are not randomly choosing mudflats on a whim.

Yellow 57 – also known as Y57

The stopover-site clusters of registrations were all located on or near coasts, except for one, used briefly, on sandbanks in the Irrawaddy River, Myanmar. Most clusters included areas of intertidal mudflats, especially on estuaries. However, a few included other habitats, such as saltpans and fishponds in impounded areas which had previously been intertidal. Ten of the 28 clusters have some protection under national legislation or international agreements, a further eleven clusters are recognised as Key Biodiversity Areas and/or East Asian-Australasian Flyway Network Sites, but seven clusters appear to have neither protection nor international recognition.

The lack of protection of wintering sites is of concern because of continuing threats to Spoon-billed Sandpipers and their habitats. Hunting of Spoon-billed Sandpipers remains a problem, for instance. This is illustrated by a story from the paper.

During a visit to site Guankoudu (Fujian Province, China) in December 2016, occasioned by the tracking of one of the tagged birds, many mist-nets, more than 2 km in total length, were found, some of which held entangled live and dead shorebirds. This site has no legal protection, but this illegal bird-trapping was reported to local government agencies, whose staff quickly began the removal and destruction of the nets.

If sites are identified, protection is possible.

There may be a Spoon-billed Sandpiper in this cloud of waders over the Taiozini Mudflat

Background to this work on Spoon-billed Sandpipers

The Spoon-billed Sandpiper conservation programme, which includes research, site protection, conservation breeding and head-starting, is a collaboration between the Wildlife & Wetlands Trust (WWT), Birds Russia, Moscow Zoo and the RSPB, working with colleagues from the BTO, BirdLife International, ArcCona, Nanjing Normal University, Spoon-billed Sandpiper in China, Hong Kong Waterbirds Ringing Group, Microwave Telemetry and the Spoon-Billed Sandpiper Task Force.

The project is supported by WWT, RSPB, the UK Government’s Darwin Initiative and SOS – Save our Species, with additional financial contributions and support from BirdLife International, the East-Asian Australasian Flyway Partnership, the Convention on Migratory Species, Heritage Expeditions, the Australasian Wader Study Group of Birds Australia, the BBC Wildlife Fund, Avios, the Olive Herbert Charitable Trust, the Oriental Bird Club, British Airways Communities & Conservation Scheme, New Zealand Department of Conservation, the Queensland Wader Study Group, New South Wales Wader Study Group, Chester Zoo, Wader Quest, Dutch Birding, OSME and British Birds Charitable Trust and many generous individuals. Leica Camera AG is WWT’s exclusive optic partner for this key conservation project.

An assessment of the conservation status of the species can be found on the BirdLife International site:

To read more about the project to set up a captive breeding population and head-start Spoon-billed Sandpiper chicks in their Russian breeding grounds visit the Saving Spoon-billed Sandpiper website.

There is lots of information on the conservation action to protect the species on the Saving the Spoonbill Sandpiper website and on the East Asian-Australasian Flyway Partnership Website. Here’s one example.

Many wader species on the East Asian-Australasian Flyway are threatened by habitat loss, as discussed in this WaderTales blog.

Paper in Wader Study

Post-breeding migration of adult Spoon-billed Sandpipers Qing Chang, Evgeny E. Syroechkovskiy, Guy Q.A. Anderson, Pyae-Phyo Aung, Alison E. Beresford, Kane Brides, Sayam U. Chowdhury, Nigel A. Clark, Jacquie A. Clark, Paul Howey, Baz Hughes, Paul Insua-Cao, Yifei Jia, Elena Lappo, Katherine K.S. Leung, Egor Y. Loktionov, Jonathan Martinez, David S. Melville, James Phillips, Chairunas Adha Putra, Pavel S. Tomkovich, Ewan Weston, Jenny Weston, Nikolay Yakushev & Rhys E. Green. Wader Study 127(3): doi:10.18194/ws.00201

UPDATE: How many Spoon-billed Sandpipers?

As discussed above, Nigel Clark, Rhys Green and colleagues previously estimated the world population of adult Spoon-billed Sandpipers at 420-456 individuals, based upon counts and sightings of individually-marked birds at a staging area on the Jiangsu coast of China. Adding in juveniles, produced an estimated population of 661-718. (Clark et al)

In a 2021 paper in Wader Study, Rhys Green and colleagues have used ten similar counts and scan samples of marked birds from China, Myanmar and Bangladesh, conducted during the period 2014-2019, to produce an updated estimate of 490 breeding-age adults (95% CL = 360-620). Adding in immature birds increases the total to 773 individuals of all ages (95% CL = 569-978). The 2021 estimate is similar to the previous one but increased geographical coverage and a larger number of surveys confer a higher level of confidence in its precision.

From the trend in the ten estimates during the period 2014-2019, it looks as if the world population of breeding adults has continued to decline at about 8% per year. This estimate of trend is not very precise but its rate is of similar magnitude to the 9% per year obtained using repeat wintering surveys in Myanmar (2009–2016). This apparent decline is less drastic than the estimated rate of loss in the period up to 2008, when there was a 26% per annum drop in the number of adult pairs across a sample of sites in the breeding grounds.

The possible slow-down in the rate of decline follows huge efforts to protect key wintering areas and staging sites, and a head-starting programme that has seen 206 chicks reared and released in the Meinypil’gyno area (2012-2020). Spoon-billed Sandpipers still seem to be heading towards extinction, but not as quickly. This emphasises the importance of finding and then increasing the protection of more staging and wintering sites, as identified in the tracking paper (see above).


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Flagging up potential problems

Any device that is added to a bird (or other animal) has the potential to affect the way it behaves. Even something as simple as a metal ring could increase risk, if it is fitted incorrectly or if fishing line gets caught around it, for instance.

In a 2020 paper in Bird Study, Thomas Mondain-Monval and colleagues report on the way that differently mounted geolocators affect Common Sandpipers. These devices were being used to help understand the migratory behaviour of the species, part of a Lancaster University PhD project that aims to explain a rapid decline in breeding numbers in England.

Safety first

Any researcher who uses rings, colour-rings, tags or tracking devices to study waders needs to ask (and answer) the following four questions:

  1. Is there a good reason to use the device? What’s the question and will the results be analysed and published?
  2. Is the device being fitted as safely as possible? Has it been used on similar species and what happened?
  3. How do the birds react to the device? If trying something new, perhaps the device can be trialled on captive birds.
  4. Are there any differences between birds wearing different types of rings or devices? Write up your results so as to help future researchers.

Thomas and his colleagues have followed this process through to its conclusion by writing a paper that is published in Bird Study. In it, they compare return rates for Common Sandpipers wearing rings and geolocators and detail a number of injuries that could potentially be linked to the geolocators.

Ringing a Common Sandpiper, before adding a colour ring and a flag

Common Sandpipers

The latest Breeding Bird Survey data suggest that numbers of breeding Common Sandpiper dropped by 40% in England and 24% in Scotland between 1995 and 2018. Over the longer period covered by the three BTO-led breeding Atlases (1968-1972, 1988-1991, 2008-2011) there have been losses from the edge of the species’ range, suggesting that decreases were already under way before the start of BBS recording period (see map). Common Sandpiper was added to the Birds of Conservation concern amber list in 2009. There are insufficient data from the BTO Nest Record Scheme to work out whether declines may be linked to breeding success.

Common Sandpipers in the River Lune study area nest close to running water

The European population of Common Sandpiper has seen a widespread, moderate decline since 1980, indicating that there may be large-scale drivers of losses. Is something going wrong in the non-breeding grounds? Previous geolocator studies have shown that Common Sandpipers rely upon a series of stopover sites on migration (see Not-so-Common Sandpipers) and it is possible that these are declining in quantity and/or quality.

As part of his Lancaster University PhD, Thomas Mondain-Monval’s PhD took a two-pronged approach to an investigation of migration routes. He added geolocators to flags on birds in both England and Senegal. The fact that different tags were used in the two countries enabled him to compare the tag effects on study birds. He was also able to compare tagged birds to a sample of colour-ringed birds.

The study systems

UK fieldwork was carried out in the River Lune catchment area in Cumbria, a northern county of England, as part of a detailed study of 24 breeding pairs. Unmarked adults were caught each year and fitted with a BTO metal ring, a yellow colour-ring (engraved with two unique black characters) and a plain red ring or flag. Similar colour rings were used on Common Sandpipers that were caught on their wintering grounds in Djoudj National Bird Sanctuary, Senegal.

Red flags were used on birds that carried geolocators as these provided space to affix the device. This sample consisted of 22 individuals in the UK and 10 individuals in Senegal. The control samples of birds with colour- rings but no geolocators were 28 individuals in the UK and 6 individuals in Senegal. Dimensions of flags and geolocators are provided in the paper, together with information on methods of attachment. The combined mass of the geolocator, flag and glue was 1.1 g for the birds ringed in England and 1.0 g for the Senegal birds, which is about 2% of body mass of the 50 g Common Sandpipers. The Senegal tags were slightly lighter but a little longer. See paper for details.

Mist nets, drop traps and whoosh nets were used to catch Common Sandpipers that were wintering in the Djoudj National Bird Sanctuary in Senegal

The Common Sandpipers in the UK were observed at least weekly throughout the breeding season. Tagged birds wintering in Senegal remained site-faithful and were observed opportunistically, usually weekly for up to five weeks following capture. It is unusual for researchers to be able to monitor the behaviour of tagged birds as closely as was the case here. When it became apparent that two birds belonging to the breeding study had started to limp, attempts were made to catch the birds. One bird was retrapped and the orientation of the geolocator was changed from parallel to the leg to along the line of the tag. This bird stopped limping and the parallel orientation was not used again.

Flag & geolocator effects

Common Sandpiper in Senegal, wearing a flag-mounted geolocator

The key measures of success that are usually monitored by researchers indicated no difference between birds with and without geolocators:  

  1. For the English, breeding population, there were no significant differences between the return rates or return dates of birds with geolocators and those without.
  2. There were no significant differences in hatching success or fledging success between birds with and without geolocators in either 2017 or 2018, although sample sizes were small.
  3. There was no significant difference in condition between birds with and without geolocators.

Most researchers who deploy geolocators on waders are using them to collect a year’s worth of data from their study birds. Typically, a bird is caught on its nest in one year and then caught again a year later – which might sound easy but isn’t! The fact that Thomas was also studying his small population in detail provided extra opportunities to collect information which should be helpful to others. Although there were no detectable effects of geolocators, as assessed using the metrics described above, a small number of individuals tagged in the UK experienced injuries:

  1. One of the birds that had been fitted with a parallel-mounted geolocator sustained an injury to its lower leg, possibly due to a constriction of blood flow. The bird was still able to continue with its breeding attempt.
  2. On their recapture in 2018, two of the seven birds carrying parallel-mounted geolocators were noted to have bruising on the tarsus, apparently caused by the geolocator hitting the lower leg whilst the bird was walking.
  3. In five cases, individuals had a slightly swollen tibia or had lost some skin underneath the leg flag. This occurred irrespective of tag orientation and appeared to be caused by the internal diameter being marginally too small for the individual, although no rubbing was noted and all flags rotated freely at the time of fitting.
  4. In Senegal, no injuries were seen on any of the tagged birds. These birds were wearing similar flags but carried lighter geolocators than the English birds.

The research team concluded that injuries to the legs of some of the study birds were caused by carrying geolocators. They suggest that they were probably due to a combination of geolocator size and weight, and the short tibias of Common Sandpipers. Mounting long geolocators parallel to the leg on species with short tibias may impede leg movement. When the team switched to thinner and lighter tags for their work in Senegal there were no problems.

It is good that Thomas and his colleagues have published the information about the issues associated with the original tagging method that they used, so that others can learn from their experiences. Had they simply reported return rates and measures of reproductive success their results would have suggested that geolocators had no negative effect on these Common Sandpipers. It would have been easy to miss out the extra detail about the small risk of leg injury.

Bird ringers are always aiming to improve catching, handling and tagging techniques. Within the UK, the use of flag-mounted or harness-mounted geolocators requires project-by-project approval from the BTO’s Special Marks Technical Panel. Annual reporting enables the SMTP to update guidance for other researchers.

Refining the way that flags are used

Flags have been used on waders for over forty years and only occasionally have birds seemed discomforted by being asked to wear them. This seems more likely to happen if the flag is applied to the upper part of the leg. When occasional individuals are observed leg-flicking it may be because the ring sits awkwardly on the tibia-tarsal joint. The flick is thought to rotate the flag into a more comfortable position. Nigel Clark, who affixed his first flag to a Dunlin in 1978 suggests the following remedies:

  1. It goes without saying that the edges of all colour-rings and flags should be sanded to remove sharp edges.
  2. Flags are heavier than colour-rings and this means that they sit more firmly on the tibia-tarsal joint, at a point which is wider in diameter than that of the rest of the tibia. When making flags the internal diameter may need to be slightly larger than that used for colour-rings on the same species.
  3. The addition of a geolocator further increases the mass of the flag. When there were concerns about flag-mounted geolocators in North America, Ron Porter solved the problem by making sure that there was a colour-ring underneath the flag. The ring rotates easily, acting as a ‘washer’ between the tibia-tarsal joint and the flag.
  4. When a wader is very thin, as it may be after a long flight, the diameter of the leg can sometimes be less than expected for the species. In Spoon-billed Sandpipers, where there is only space for one ring on the tibia, flagged birds have occasionally been seen leg-flicking. When the leg-flags were modified, to reduce the internal diameter, things improved.

If there is a paper that describes or expands upon the above list, I shall be delighted to add a reference.

To learn more

This blog focuses on a 2020 paper in Bird Study, the journal of the British Trust for Ornithology:

The effects of geolocators on return rates, condition and breeding success in Common Sandpipers. Thomas O. Mondain-Monval, Richard du Feu and Stuart P. Sharp

Three previous WaderTales blogs have discussed issues relating to flags and geolocators:


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Cycling for waders

This blog is mostly about Black-tailed Godwits but there’s stuff about cycling too!

If you’re a Black-tailed Godwit, a 2800-mile (4500-km) direct flight from East Anglia to West Africa is estimated to burn 1085 Calories (4500 kJ) of energy (Alves & Lourenço). Fuelled by Cambridgeshire worms, a female godwit that was raised by the Project Godwit head-starting team flew from the Nene Washes to wetlands in south-east Mauritania in just two days. ‘Cornelia’ – as she was named – undertook this marathon journey with no pre-season training. She just took off on 13th August and arrived on the 15th.

To raise money for Project Godwit and for research projects funded by the International Wader Study Group, Jen and Mark Smart cycled from Somerset to East Anglia, on a 600 mile (960 km) journey that links sites that have been visited by head-started Black-tailed Godwit chicks. Each of them burnt 15,000 Calories (62,800 kJ) over the course of eight days, taking in high energy foods as they travel and stopping to feed and rest each night. Unlike Cornelia, Mark and Jen had been training for years.

Quick reminder of head-starting

Black-tailed Godwits breeding in East Anglia face huge challenges, as you can read below. Four years ago, their situation had become so perilous that it was decided that the only way to stop them disappearing completely was to hatch eggs in incubators and raise chicks in captivity. You can read more about head-starting here. Project Godwit is a partnership between RSPB and WWT, with major funding from the EU LIFE Nature Programme, the HSBC 150th Anniversary Fund, Natural England, the National Lottery Heritage Fund through the Back from the Brink Programme, Leica and the Montague-Panton Animal Welfare Trust.

The maps below show the two breeding sites (Ouse and Nene Washes) and all the late-summer passage sites where head-started birds have been seen in England (left), and the international sightings of all godwits ringed in these breeding sites.

International Wader Study Group (IWSG)

The International Wader Study Group brings together everyone who has a passion for waders (shorebirds), the habitats they use and their conservation. Members include research scientists, citizen scientists and conservation practitioners from all around the world. IWSG gives out small grants each year that help to support wader projects around the world. Recent grants have been used to discover the wintering areas of Common Sandpipers, to measure the site-faithfulness of Dotterel and to support projects in Azerbaijan, Albania, Bangladesh & Argentina.

Mark and Jen

Jen Smart has worked for the RSPB for 14 years.  As a scientist, she led RSPB’s research into the conservation problems faced by breeding waders and developed solutions to help these species. See the WaderTales blog Tool-kit for wader conservation. She developed the science programme around Project Godwit and maintains a keen interest in the project. Jen is Chair of the International Wader Study Group.

‘Manea’ arrived at Old Hall Marshes (Kent) with his sister, ‘Lady’, in July 2017

Mark has worked for the RSPB for 26 years and is Senior Site Manager at Berney Marshes, a 600 ha grassland nature reserve with around 300 pairs of breeding waders. See the WaderTales blog Managing water for waders. As well as managing the reserve, Mark works with other land managers across the country to develop and implement ways of improving habitats for breeding waders.

Latest news from Project Godwit

Project Godwit has been trialling the use of head-starting (https://projectgodwit.org.uk/), where young godwits are reared in captivity, safe from predators and potential flooding, and released once fledged. The aim is to boost the number of godwits breeding in England. The cycle route for Mark and Jen links eleven nature reserves in England, managed by a range of conservation organisations, where head-started Black-tailed Godwits have been spotted on migration by local birdwatchers.

Nelson is one of the birds carrying a geolocator but he has not been recaught (yet)

The ride started at WWT Steart Marshes in Somerset; visited by a Black-tailed Godwit named ‘Nelson’ in 2017. Birdwatchers throughout England were put on alert when the first head-started Black-tailed Godwits were released in 2017 but it was a surprise when Nelson headed southwest. Nelson is a star of Project Godwit. He returned to the Ouse Washes in 2018 and paired up with another head-started bird called ‘Lady’. They have met up in each subsequent spring. In February, Nelson spends time on the Tagus Estuary in Portugal but we don’t know whether he is one of the limosa Black-tailed Godwits that winters south of the Sahara.

The map below shows the route taken by Mark and Jen. The original plan was to cycle from Norfolk to the IWSG conference in Germany, which neatly linked the two causes for which they are seeking sponsorship – Project Godwit and the IWSG fund to support wader research. When the conference was rescheduled as an on-line meeting, they decided to join up the godwit dots across England. The 600-mile bike took just over a week.

Jen & Mark’s route links RSPB, WWT, Wildlife Trustand county wildlife sites between Somerset and Cambridgeshire.

The last site to be visited was the Nene Washes where, as mentioned above, the Black-tailed Godwit ‘Cornelia’ returned to breed. Having been raised at Welney, she was released at the Nene Washes on 27 June, 2018, wearing a small geolocator attached to a flag on her lime ring (see earlier picture). She is the only bird for which the RSPB and WWT team have a whole-year migration history. Cornelia was caught on a nest at the Nene Washes in 2019 and her geolocator was removed. In his blog on the Back from the Brink website, Mo Verhoeven shares his excitement when he learned that this young bird had flown directly from the Nene Washes to wetlands in Mauritania in just two days. There is more about Cornelia here.

Conservation challenges

Wetlands are under threat across the globe and it is appropriate that Mark and Jen are raising money for the International Wader Study Group and for Project Godwit. As they tweeted about their travels and talked about Black-tailed Godwits at local press events, at different nature reserves, they revealed some of the conservation challenges that waders face.

The RSPB nature reserve at Titchwell (North Norfolk) is a favourite pit-stop for Project Godwit birds. These three youngsters, all head-started in 2018, visited before flying south.

Project Godwit is not just about head-starting more Black-tailed Godwit chicks. The team is trying to improve the chances for nesting birds out on the Washes, using electric fences and other predation reduction schemes, and through the development of alternative breeding areas that are under less threat of flooding during spring and summer deluges.

Within Britain and when they head south through Europe and into Africa, Black-tailed Godwits are dependent upon a network of sites. Some of them are fully-protected nature reserves, others have been given international recognition as SPAs and Ramsar sites, but there are many other locations that are important but not designated. Sightings of Project Godwit birds and locations downloaded from geolocators will help to identify areas in which birds may be vulnerable to habitat change and new developments.

A new airport that is planned for the Tagus Estuary is a huge threat to limosa Black-tailed Godwits that breed in Western Europe, including the small English population. It’s thought that about half of the Project Godwit birds use the rice fields and mudflats of the Tagus Estuary, as you can read in Black-tailed Godwits are on their way home. As mentioned above, Nelson has been seen in the Tagus Estuary on several occasions (see map alongside). The proposed airport threatens many species of migrant waterbirds (Tagus Estuary: for birds or planes).

An important unknown when trying to conserve our larger wader species is ‘what happens to the teenagers?’. When do species such as Black-tailed Godwits start to breed and what do they do in the period between fledging and breeding? A key part of Project Godwit is to mark chicks in the wild, as well as head-started birds, hopefully answering questions such as ‘what proportion breed in their first year?’ and ‘where do immature birds spend the pre-breeding years’? Perhaps the International wader Study Group will be able to support similar work for other large shorebird species, through its small project grants?

Support for Mark and Jen

This epic sponsored cycle ride is funding work by Project Godwit and the IWSG. It was a great opportunity to thank colour-ring readers who have reported marked birds, to emphasise the importance of protecting networks of sites for migrant waders, and to highlight some of the conservation challenges that lie ahead.

If you would like to help Mark and Jen to support International Wader Study Group Small Projects Grants, please donate here: https://www.waderstudygroup.org/donate/

If you would like to help Mark and Jen to support the RSPB’s contribution to Project Godwit please donate here: https://www.justgiving.com/fundraising/fundsforwaders


WaderTales blogs are written by Graham Appleton (@GrahamFAppleton) to celebrate waders and wader research. Many of the articles are based on published papers, with the aim of making shorebird science available to a broader audience.

Trees, predators and breeding waders

When trees are planted in open habitats that support breeding waders, numbers usually decline pretty quickly. Trees not only directly remove once-occupied habitat, they are also thought to attract predators, by providing somewhere to hide. In their paper in Restoration Ecology, Mark Hancock and colleagues investigate the distribution of thousands of scats of mammalian predators, in order to understand predator activity in landscapes associated with open bogs and forest edge. They were particularly interested in seeing how long it takes for predators to move out of an area when trees are removed and the land once more reverts to blanket bog.

This study took place alongside a project to repair damage to the vast Flow Country blanket bog (northern Scotland), that occurred in the 1980s, when non-native conifer trees were planted in areas of deep peat that had been drained and deep-ploughed. Such forestry practises would nowadays be prohibited.

More trees

The spread of trees can occur naturally, as the northern treeline moves further north or as trees grow higher in mountain regions, or it can be imposed or accelerated when trees are planted in previously open environments. Warmer temperatures create more opportunities for afforestation and politicians seem to be responding to rising CO2 levels by opting for what seems like an easy win – ‘let’s plant more trees’. In the right places, using appropriate native species, woodland can help to capture carbon**, support woodland wildlife and provide multiple other benefits to society. However, if afforestation focuses on open wet landscapes it can potentially threaten ground-nesting wader species such as Dunlin and Curlew.

** link to The value of habitats of conservation importance to climate change mitigation in the UK by Rob Field and colleagues in Biological Conservation.

As Mark Hancock and colleagues indicate in the abstract of their paper, afforestation of formerly open landscapes can potentially influence mammalian predator communities, with impacts on prey species like ground-nesting birds. In Scotland’s Flow Country, a globally important peatland containing many forestry plantations, earlier studies found reduced densities of breeding waders on open bogs where forestry plantations were present within 700 m. See Hancock et al. 2009 and Wilson et al. 2014. A previous WaderTales blog discussed whether apparent avoidance is due to actual or perceived predation risk (See Mastering Lapwing conservation) but whichever it is, adding new woodland to open wetland habitats has the potential to affect sensitive breeding waders.

Fox scat

There have been many studies looking at the effects of trees on breeding waders but the key differences in this case were that researchers monitored how mammal distributions changed as woodland was removed, in an effort to restore biodiversity and valuable blanket-bog habitats. Spoiler alert: it takes several years to reduce predator numbers!

By counting scats of species as diverse as fox and hedgehog the team were able to address three questions:

  • Did scat distributions vary between open bog, forestry plantations, and former plantations being restored as bog (‘restoration’ habitats)?
  • How fast did scat numbers change in restoration habitats?
  • Were scat numbers different in bogs with differing amounts of nearby forestry?

Counting the poo

Forestry transect

The analyses in this paper are based upon surveying 819 km of track verges, which yielded a total of 2806 scat groups (groups of scats that could have come from one animal) from a variety of predators. I smile when days and days of painstaking fieldwork are summarised in a sentence. “We measured summer scat density and size over 14 years, in 26 transects 0.6-4.5 km in length, collecting data during 93, 96 and 79 transect-years in bog, forestry and restoration habitats respectively”. There is no mention of midges either!

The Flow Country is host to a range of predatory mammals. Hedgehog, Wildcat, Red Fox, Badger, Pine Marten, Stoat and Weasel are native species, while introduced species like Feral Ferret and American Mink may be threatening the area. A 10 mm diameter scat could have been produced by one of six or more species – and increasingly it has been shown that genetic methods, which were outside the budget of this study, are needed to properly identify species from a scat. As all of these species prey on the eggs and/or chicks of breeding waders, the study treated them as a ‘guild’ of animals having similar potential effects.

In April each year, fieldworkers – many of them volunteers based at RSPB’s Forsinard Flows reserve – walked along each of the transects, removing all of the scats from the tracks and track-edges. In July, scats and scat groups that had been deposited on the tracks during the breeding season were counted, measured and their positions recorded using GPS (see paper for details).

Nine transects were in open bog habitat, that remained broadly unchanged throughout the study, 8 were in forestry plantations, 8 were in forestry plantations that were cleared and then restored during the study and 1 site was already a restored plot. For ‘restoration’ transects, the number of years since felling was used as a measure of the length of time under restoration management. In these restoration areas, the brash that was left after felling gradually rotted away or became buried by recovering bog vegetation as re-wetting management (e.g. drain blocking) took effect.

Where’s the poo?

Transect through bog

Predator activity in different habitats and over time. For bog and restoration habitats, scat group density was relatively low throughout the study, averaging around 1 to 2 scat groups per km. In forestry transects, scat group densities started at similar values, but rose approximately eight-fold over the study period, as the forests matured. In the final year of the study, scat group densities in forestry averaged around eight groups per km – approximately twice the figures in restoration and six times the figure in bog habitats. There is a suggestion that more mature forests may have suited Pine Martens, in particular: this species was recorded in the heart of the Flow Country for the first time during the study period.

Trees removed – restoration transect

Predator activity once trees are removed.  Scat group density differed significantly between restoration areas of different age classes. In recently-felled sites (1-5 years), densities were about 2.4 groups per km, rising to 4.0 in the middle period (6-10) and falling to 1.3 later (11-14 years). The authors suggest that tree removal may lead to a flush of nutrients, grasses and then small mammals, thereby explaining the increase in scat densities during the middle stage (6-10 years). The paper demonstrates that it takes several years for mammal densities to fall back to ‘natural’ levels, after tree removal.

Pine Martens have moved into the area

Predator activity close to forests. Scat density on open bog transects was significantly affected by the presence of at least 10% forestry cover within 700 m. There was an estimated 2.9 times (95% confidence limits 1.4 to 6.0) higher scat density at bog transects which contained over 10% cover of forestry within 700 m, compared to bog transects with less forestry nearby. Scottish studies of breeding waders have shown that species such as Golden Plover, Dunlin and Curlew avoid areas close to forestry and the paper includes references to several other similar studies elsewhere.

The Conservation picture

As pointed out by Hancock et al in their Discussion, scat densities in forestry reached much higher values than those of open bogs, especially as the plantations matured, implying that afforestation had strongly altered patterns of mammalian predator occurrence in this formerly open landscape. It took ten years of restoration management to drive down scat densities to levels similar to those of open bogs but, as the authors note, peatland restoration is a rapidly developing field and newer techniques may allow faster restoration, with both biodiversity and soil carbon benefits.

These findings have implications way beyond the scope of this study, three examples of which are included below:

Commercial forestry is seen by some as a way of capturing carbon and can provide opportunities to restore our woodlands, especially our native woodlands and their associated biodiversity. However, given the vulnerability of ground-nesting birds to predation, and the potential for afforestation to markedly affect predator communities, care needs to be exercised when considering afforestation of open landscapes.

Warmer climates offer opportunities to add forestry to the mix of land use options in areas in which the growing season used to be considered too short. For instance, there is significant development pressure in Iceland to plant large areas of non-native commercial forestry. Given that the country holds half or more of Europe’s breeding Whimbrel, Dunlin and Golden Plover this is a contentious issue. This AEWA report is important: Possible impact of Icelandic forestry policy on migratory waterbirds.

In Ireland, it has been suggested that a patchy distribution of relatively new forestry plantations may be one of the factors contributing to the drastic decline of Curlew numbers. (Ireland’s Curlew crisis describes a 96% decline in just 30 years). It has been proposed that some of these patches should be removed. The Hancock et al paper shows how long it might take to make a difference – ten years may simply be too long for Ireland’s breeding Curlew.

Read more

The paper that forms the basis of this blog is:

Guild-level responses by mammalian predators to afforestation and subsequent restoration in a formerly treeless peatland landscape by Mark H. Hancock, Daniela Klein and Neil R. Cowie. Published in Restoration Ecology. https://onlinelibrary.wiley.com/doi/abs/10.1111/rec.13167


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Plovers from the north

Despite its global distribution, the Grey Plover (or Black-bellied Plover in the Americas) does not get the attention it deserves, according to Andrew Darby, author of Flight Lines, a book about shorebird migration and Grey Plovers in particular.

Who would want to study a shorebird that is the first species to sneak away from its tundra nest when danger threatens, and that is hard to catch outside the breeding season? Fortunately, satellite technology means that a lot can be discovered by following just a small number of birds and this blog will focus on two individuals, setting their travels within a broader flyway context.

Flight Lines

Grey Plovers CYA and CYB are the stars of Flight Lines, a book by Andrew Darby which takes us ‘across the globe on a journey with the astonishing ultramarathon birds’. They were caught together in Adelaide’s Gulf St Vincent by members of Victoria Wader Study Group on 14 November, 2015. Here, they were carefully fitted with tags that were originally to be deployed on Bar-tailed Godwits. So starts a story that takes us from the south coast of Australia to islands off the north coast of eastern Siberia, via the Yellow Sea.

Andrew has not simply written a bird book; Flight Lines tells the sort of tale that I remember from school days, of how Cook and Magellan travelled the globe or Livingstone and Stanley ‘discovered’ Africa. Grey Plovers have been flying to the Arctic for millennia – from Europe, Africa, Asia, Australasia, the USA and South America. CYA and CYB are doing what their ancestors have always done. As we follow their journeys, Andrew tells us about the habitats these birds need, shares stories about the lives of local people who await their arrival, reveals the way that shoreline ‘development’ is impacting upon their survival and tells us about some of the ornithologists who are  encouraging governments and local communities to save space for the birds with black wing-pits (see picture below).

Territoriality

Grey Plovers travel vast distances across the globe but once they have arrived at their final destinations they are highly territorial – and not just in the breeding season. When David Townshend studied marked individual Grey Plovers feeding on the Tees, in north-east England, back in the late 1970s, he discovered that they fed in the same places for the four-month period of the winter, defending their patches against interlopers; what’s more, they returned to these territories in subsequent years. It’s like running a marathon and then not leaving your back yard until it’s time to take off again, months later.

As Andrew Darby reminds us, Grey Plover can re-visit the same territories for decades; something to remember when considering what happens when a coastal development steals the ‘homes’ of all of the Grey Plovers in a bay. How does a twenty-year old bird find a new home? There’s a WaderTales blog about longevity records for waders/shorebirds.

Territoriality is not just a British thing. In Flight Lines we learn that the same is true for American Black-bellied Plovers wintering in San Diego and Grey Plovers in South Africa’s Eastern Cape. Here, tracking has shown that the patterns that David Townshend witnessed by day are maintained during the night. Those big eyes can make the most of low light-levels. A hungry individual stands still and waits for prey to move, gives up after a while and tries another likely patch within its territory. Plovers are not like Knot; they don’t have a sensitive tip to the bill that can detect hidden prey, their hard-tipped bills grab items from the surface of the mud or sand, guided by those big, black eyes.

Global distribution

According to BirdLife International, the global population of Grey Plover is only about half a million birds, 80,000 of which use the East Asian-Australasian Flyway. This system of aerial ‘motorways’ links countries as diverse as New Zealand and Thailand with breeding areas in the East Russian Arctic and Alaska.

There is a temptation to sit at home and think of migration as something that happens in a line that runs north to south and back again. Fifty years ago there was an assumption that Black-bellied Plovers would migrate north and south within the Americas, that Grey Plovers in western Europe and Africa would be linked to western Siberia, that Australian birds bred in eastern Siberia, and that Grey Plovers in southern Africa, the Arabian peninsula, India etc  would be birds that had flown from ‘the middle bit’ – between western and eastern Siberia.

Studies of other shorebirds have shown more cross-overs than might have been expected, breaking up the neat south-north pattern. Chukotka, for instance, indicated by the red star on the BirdLife map, is a summer home for Ringed Plover from Egypt (Well-travelled Ringed Plovers), Spoon-billed Sandpipers from Bangladesh, Knot from Australia and Buff-breasted Sandpipers from South America.

Shorebird mixing happens on the other side of the Bering Sea too. Shorebirds that fly to Alaska from South America in spring are joined by Bar-tailed Godwit that fly north from New Zealand, via the East Asian coast. These baueri race Bar-tailed Godwits are famous migrants – they fly non-stop all the way to New Zealand come fall/autumn. See paper by Phil Battley et al.

So, what about Australian Grey Plovers? Do they meet up with American Black-bellied Plovers?

Linking wintering and breeding areas

As Andrew Darby tells us in Flight Lines, measurements of Grey Plovers in Australia and in Russian breeding areas suggested that wader experts Clive Minton and Pavel Tomkovich were handling the same birds in Victoria and on Wrangel island, north of the Russian mainland. In 2007, Pavel banded some Grey Plovers, the hope being that one of them might be seen in Australia. The only one of these Grey Plovers ever to be reported was seen in the Chinese part of the Yellow Sea – six years later.

The Grey Plover colour-ringed by Pavel was spotted by David Melville, who has done a great deal to fill gaps in knowledge about the vast flocks of waders that use the Yellow Sea, including significant numbers of passage Grey Plover. One of the wonderful features of Flight Lines is the way that it turns names into characters. I had heard of many of the people who Andrew met or spoke to, during research for the book, but I appreciate their roles much better now. There is fantastic work taking place in countries throughout the Flyway, ably coordinated through the East Asian-Australasian Flyway Partnership.

Given that colour-ringed Grey Plovers were not providing the data that could link breeding and wintering grounds, it was time to try something new. On 14 November, 2015, CYA and CYB were fitted with satellite transmitters and in March they flew north. In the same way that we read that Captain Cook ‘discovered’ Australia, without telling the story of the challenges his crew faced on the way, I am just going to present the map of the northward journeys of the two birds and leave you to read Flight Lines, the log-book of their journeys.

The map shows the positions on 7 June 2016, whe CYA and CYB had only just arrived on Wrangel Island. The journey north is described by Tony Flaherty in Victoria Wader Study Group Bulletin number 39.

“The two satellite transmitters, put on to Grey Plover in South Australia by Maureen Christie’s team in November, 2015, have performed brilliantly, with both birds successfully migrating northwards, including a long stop-over in the Yellow Sea, and eventually going on to breed on Wrangel Island off the north coast of Chukotka, eastern Siberia. This is the first evidence of any bird from Australia visiting this remote Arctic Island. At the time of writing this, both are now on their way back from the Arctic, with one having made a surprising major detour via the New Siberian Islands.”

There is a complementary article about the journey south in the next issue of the VWSG Bulletin, also by Tony Flaherty.

Map data courtesy of Victorian Wader Study Group & Friends of Shorebirds SE. The project was made possible by support from the Australian Government and the Adelaide and Mt Lofty Ranges Natural Resources Management Board.

A conservation agenda

One of the major drivers of bird ringers/banders is a thirst for knowledge – and there is nothing wrong with that spirit of enquiry. For the East Asian-Australasian Flyway there is a deeper imperative; conservation of birds using habitats that are under immediate threat from human exploitation and climate change. A previous WaderTales blog – Wader declines in the shrinking Yellow Sea – focuses on a paper that highlighted the desperate need to understand and conserve shorebird populations. One species that hardly gets a mention in that paper is the Grey Plover. It’s not that there is no threat to Grey Plovers, it’s just that there were insufficient data. It’s not easy to study these territorial plovers, which are thinly spread throughout the non-breeding range and difficult to catch.             

About Flight Lines

The WaderTales blog series started out as a planned book about Black-tailed Godwits but I found that I did not have the stamina to weave together science tales into an interesting tapestry. Andrew Darby is a master of the writing craft. Although he focuses upon waders, and the Grey Plover lead characters, he also tells us about the pioneer ornithologists who have explored the East Asian-Australasian Flyway, in search of shorebirds that spend Christmas and New Year in Australia and New Zealand. Flight Lines is published by Allen & Unwin. ISBN 978 1 76029 655 1

Migration research about other Grey Plover populations

Papers about Grey Plover and Black-bellied Plover are thin on the ground but new projects on the East Atlantic Flyway and in the Americas are starting to fill in some of the gaps in our knowledge.

The Wash Wader Ringing Group has ringed/ banded over 6500 individual Grey Plovers since the Group was founded in 1958 (Sixty years of Wash waders). Their work was written up in 1976 by Nick Branson and Clive Minton (Moult, measurements and migrations of the Grey Plover). The map alongside shows movements of birds to and from the Wash.

Recent research by Klaus-Michael Exo and colleagues has used satellite tracking to understand better the movements of Grey Plover breeding in the Taimyr and Yamal regions of Siberia. In their paper, they identify important staging sites as well as wintering areas between Ireland and Guinea Bissau. Tagged birds stopped off for long periods during migration, especially in late summer and autumn. See Migration routes and strategies of Grey Plovers on the East Atlantic Flyway as revealed by satellite tracking.

The Tidal Wings project focuses on Grey Plovers that winter in the Bijagos archipelago of Guinea Bissau. You can keep up to date on their discoveries on their website (https://birdecology.wixsite.com/tidalwings) and on Twitter. The map above shows three migrations of the same individual.

In North and South America, the Black-bellied Plover is also receiving increased attention. There is a large collaborative project to reveal their migratory connectivity, with over 70 tags deployed to track birds from Alaskan and Canadian breeding grounds, and from Texas and Louisiana wintering grounds. Work is being conducted by the Smithsonian’s Migratory Connectivity Project, USGS Alaska Science Center, Environment Canada, Texas A&M University, University of Missouri, Brighman Young University-Hawaii, and Coastal Bend Bays and Estuaries Program. The map alongside was provided by Autumn-Lynn Harrison of the Smithsonian Migratory Bird Center and shows example migration routes from one breeding population in Nome, Alaska. 

Colour-ring studies. Satellite tags are a key part of modern wader and shorebird studies, providing immediate insights from just a small number of birds, but simple bits of plastic can play a role too, especially in Western Europe, where lots of birdwatchers visit coastal sites. Colour-ring studies in East Anglia and northwest England are revealing more about how Grey Plovers use a suite of different estuaries during the course of the non-breeding seasons and will ultimately monitor annual survival rates. It will be interesting to learn whether individual birds hold territories in each of the estuaries that they visit, to moult, spend the winter and prepare for spring migration. The importance of allocating individual leg-flags to ringed birds is discussed in Bar-tailed Godwit: migration & survival.

I look forward to seeing more papers about the Grey and Black-bellied Plover, the shorebird that breeds at the top of the world.


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton