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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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

A Rhapsody of Whimbrel

Around the globe, the seven-note whistle of the Whimbrel is a spring theme tune for shorebird migration. Where are flocks going to, as they gain height and head north in March, April and May, and why have birds chosen that particular moment to depart?

In a paper in Frontiers in Ecology & Evolution, Camilo Carneiro, Tómas Gunnarsson and José Alves analyse individual migration tracks of birds flying from West Africa to Iceland, including journeys made in successive springs by birds that have been part of the same study for several years. Can these birds help to explain how Whimbrel use time and weather cues in their travel ‘planning’ and might their plans change during the course of their lives?

Look up to the skies and see

Almost all of the Whimbrel that nest in Iceland migrate to West Africa after the breeding season, with just a tiny number wintering in Europe.

Life has just begun

The Whimbrel’s story starts in Southern Iceland. It would be great to tag chicks when they hatch, in order to learn what happens to juveniles in their first autumn, as they head south without parental guidance. For the moment, however, Camilo Carneiro, José Alves and Tómas Gunnarsson are focusing on parent birds which they have been catching on their nests since 2012.

The research summarised in the paper at the heart of this blog uses data from 66 retrieved geolocators that have been carried by a total of 39 individuals.  Light data, temperature readings, conductivity and the timing of contacts with water all help to determine the start and end points of individual flights.

Any way the wind blows?

As the authors write in the summary of the paper, “Weather conditions are important during migration, particularly wind and temperature, and can play a crucial role in the timing of events during the annual cycle of migratory birds.” Camilo and his colleagues have investigated how wind conditions, temperature and spring departure date may drive individuals to pursue either a ‘stop-over’ or ‘direct flight’ strategy in the spring. They suggest that one or two of the following scenarios might be envisaged:

Competition on the breeding grounds can be quite vigorous
  • Whimbrels may make migratory decisions prior to departure, given local weather conditions. If migratory behaviour is defined prior to departure then that would suggest that departure time from West Africa may not be associated with the wind conditions that can assist individuals on the first stage of their journeys.
  • Whimbrels may adjust migratory behaviour during flight, depending on conditions experienced en route. As birds fly north, from 37°N (level with the Mediterranean) to 50°N (SW tip of England), they can make decisions to stop off, rather than continue straight to Iceland. Potentially, they could assess the amount of support they have been receiving from favourable winds and assess the positive effect on fuel reserves. Temperature could also act a cue to weather conditions in Iceland.

Little high, little low

Wader biologists and birdwatchers will have seen flocks of waders preparing for departure from breeding, stop-over and wintering locations.  Birds become restless and groups of birds start to circle and rise into the sky.  The first, departing flock may be joined by others, taking off in small groups to catch up with birds that seem to have a plan. At the same time, birds can also be seen dropping out of the flock to wait for another day.

Once formed, a migratory flock will be made up of individuals that may be heading for points that are hundreds or (for some species) even thousands of kilometres apart but will fly together for this next leg of the journey.

Tómas Gunnarsson has seen Whimbrel circling and gaining height at departure from the south coast of Iceland in autumn, suggesting that they may assess wind conditions at different altitudes before making a final decision and setting their course south. It seems plausible that the same sort of thing might happen during spring migration from West Africa. At some stage, with a large number of tracked birds, perhaps it will be possible to study if waders sample wind speed and direction prior to departure and whether decisions made at this point affect the amount of support they receive from wind conditions when on migration. There’s a great paper about how wind affects the migration of much larger Honey Buzzards by Wouter Vansteelant.

Once in the air, birds in a migrating flock can be impeded by headwinds, assisted by tailwinds and pushed laterally by crosswinds. As has been shown when tracking trans-Pacific journeys of Bar-tailed Godwits, storms and pressure systems can provide a sling-shot effect to accelerate progress, cause birds to temporarily abort their journeys or even back-track a thousand kilometres, in order to refuel for another migration attempt.

Nothing really matters

Camilo and his colleagues compared 9 direct flights with 48 that included stops in Portugal, France, Ireland and north-west Britain. Birds that departed later tended to undertake direct flights. Interestingly, they found little evidence that conditions were linked to an individual’s migration option:

  • For individuals undertaking either direct flights or stopovers, the wind conditions at departure did not differ from winds during the previous seven days, suggesting little or no selection for wind conditions to initiate the flight.
  • Individuals on direct flights encountered similar winds as they passed through the region 37°N to 50°N (Mediterranean to SW tip of England) as those on stop-over journeys.

Too late, my time has come?

For late-departing birds that fly straight to Iceland, there is the potential to catch up with (and even overtake) birds that left earlier and subsequently stopped in countries such as Ireland. In such circumstances, one could imagine that birds still in West Africa in late spring may ‘opt’ for a direct flight. However, the wind patterns over a period of seven days prior to departure were no different to the ones at the start of a non-stop flight. There did not seem to be any weather-related reason for these birds delaying departure as long as they did.

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Camilo Carneiro is also investigating the breeding success associated with different arrival times and migration patterns

For birds that do stop-off en route in Britain and Ireland, which are relatively close to the breeding sites in Iceland, there are potential benefits, as discussed in more detail in the paper:

  • Individuals might be able to assess (remotely) the weather conditions at their breeding sites if there are links between weather patterns in Iceland and those in Ireland and western Britain. If this is the case, then they can adjust the start of the final Atlantic crossing so as to arrive in Iceland when conditions are likely to be favourable.
  • Whimbrels can feed up in Britain & Ireland, potentially arriving in Iceland in better condition than birds that have flown directly from West Africa.

Carry on, carry on

The fascinating thing about being able to track individuals is that we are starting to understand the conditions that may lead to the migration patterns we see at the population level. In other WaderTales blogs, some of the key processes and patterns have already been discussed:

Given this body of knowledge, suggesting little flexibility once an individual’s phenology is fixed, one might expect that an individual Whimbrel, travelling from West Africa to Iceland, would adopt the same migration pattern in subsequent years. Tagged Whimbrels, for which there were repeat migration tracks, mostly ‘did the same’ but not always.

Any way the wind blows, doesn’t really matter

The key finding of Camilo Carneiro and his colleagues is that weather conditions are not the main driver of different spring migratory timings in Icelandic whimbrels. As suggested in Whimbrel: time to leave (and the paper Why are Whimbrel not advancing their arrival dates into Iceland?) departure from West Africa is the most firmly scheduled point in a Whimbrel’s annual cycle. However, three birds provide an opportunity to build a modified hypothesis.

In the course of this study of Icelandic Whimbrel, thirteen birds have provided multiple years of data and there have been three cases in which birds have switched migratory behaviour, seemingly contradicting the ‘birds always do the same thing’ theory. In each case, individuals changed from ‘direct-flight’ to ‘stop-over’ and, having changed, they then repeated the ‘stop-over’ option. The fact that all three individuals made the same change hints towards individual refinement of behaviour. Since there appears to be no clear advantage to direct migration, perhaps individuals are moving to a two-stage migration when they discover that this is a possibility?

Is this just fantasy?

This is where the paper stops but it will be fascinating if the research can continue:

  • Are changes always going to be in the same direction – from ‘direct-flight’ to ‘stop-over’?
  • Most juveniles are thought to fly directly to West Africa. By tracking young birds, caught in Iceland prior to departure, perhaps it will be possible to work out the proportion of first journeys that are direct?
  • Young birds that fly south across the Atlantic will not have learnt that there is any land between Iceland and West Africa. Do they retrace their journeys when they fly north again, eighteen months later?
  • What proportion of these birds that start on the ‘direct-flight’ strategy later switch to ‘stop-over’?
  • If some juveniles stop off in western Europe, on their first journeys south, perhaps these birds also stop off on their first journeys north? That might mean that they never used the ‘direct-flight’ option.
  • And how do flocks work? Will it ever be possible to deploy enough trackers to see whether ‘direct-flight’ individuals learn that there’s an alternative option by travelling in flocks with birds that use the ‘stop-over’ strategy.

It’s all fascinating stuff about the Queen of waders!

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Anyone can see

The paper featured in this blog is: Linking weather and phenology to stopover dynamics of a long-distance migrant by Camilo Carneiro, Tómas G. Gunnarsson & José A. Alves, published in Frontiers in Ecology & Evolution.


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

Do population estimates matter?

blog top godwitsHow many waders spend the winter in Great Britain? The answer is provided within an article in British Birds entitled Population estimates of wintering waterbirds in Great Britain. It includes all the wader species from Little Stint to Curlew that are covered by the Wetland Bird Survey  This survey is based on monthly counts that take place at about 2000 wetlands and coastal sites. The main aim is to monitor the rise and falls in numbers over time.

Please note that Northern Ireland WeBS figures are included in a separate blog covering the island of Ireland that was published in Irish Birds.

Why do we need to know the total number of birds in Great Britain?

  • If we count the number of Curlew and we have a figure for the European population then we know that Great Britain is responsible for nearly 20% of Europe’s Curlew each winter, thereby strengthening the case for national conservation action;
  • If we have a national figure, then we know that a flock of 2000 Black-tailed Godwit represents (as it turns out) over 5% of the British total, which is a useful criterion when assessing the conservation importance of individual sites;
  • blog GKPopulation totals help to put annual percentage changes into context;
  • And simply because people ask questions such as “how many Greenshank are there in the country during the winter?”

So, here’s the bottom line. In their 2019 review of waterbird numbers in British Birds, a team from BTO, WWT, JNCC & RSPB reveal that an estimated total of 4.9 million waders spend the winter in Great Britain. For several species, GB holds a third or more of the East Atlantic Flyway population!

Making the counts

The population estimates owe a lot to those who undertake monthly Wetland Bird Survey (WeBS) counts on estuaries, lakes and waterways, during the winter months, year in and year out. Counts from the period 2012/13 to 2016/17 are used in the population estimates that form the basis for the 2019 review. WeBS data have many other uses, as you can read here: Wetland Bird Survey: working for waders.

blog CUFor species of wader that also make use of the open coast, the Non-estuarine Waterbirds Survey of 2015/16 (or NEWS III) provided additional data, updating the NEWS II figures from 2006/07.

The vast majority of our wintering Purple Sandpipers are found on open beaches and rocky shores, as well as large numbers of Turnstone, Ringed Plover and Sanderling, together with significant numbers of Oystercatcher, Curlew and Redshank. There’s more about NEWS in this slightly dated blog: NEWS and Oystercatchers for Christmas.

The last assessment of winter wader populations was made by the Avian Population Estimates Panel and published in British Birds in 2013 as Population estimates of birds in Great Britain and the United Kingdom (APEP3). In here, estimates for waders were largely based on WeBS data for the period 2004-09 and NEWS II. The new assessment is presented as Population estimates of wintering waterbirds in Great Britain and also published in British Birds. It uses WeBS information for the period 2012-17 and NEWS III data. Effectively, there is an 8-year or 9-year difference between the two sets of figures.

The biggest losers

blog graphicGreat Britain is extremely important in the context of the East Atlantic Flyway, as is obvious from the fact that the area holds nearly five million waders. The WeBs counts already monitor the ups and downs on an annual basis but this review provides an opportunity to turn the percentages into actual numbers. It is concerning that, over a period representing less than a decade, the average maximum winter count for six of the species that were surveyed dropped by a total of over 150,000. These big losers were Knot, Oystercatcher, Redshank, Curlew, Grey Plover and Dunlin, ordered by number of birds lost, with Knot seeing the biggest absolute decline.

In preparing the new estimates for the British Birds paper, an opportunity was taken to refine the way that populations are calculated, based on Use of environmental stratification to derive non-breeding population estimates of dispersed waterbirds in Great Britain, by Verónica Méndez et al. The new methodology explains some of the differences between percentage changes reported by WeBS and the percentage changes obtained by comparing the latest population estimates to those in APEP3.

blog KN graphic

The Knot estimate dropped from 320,000 to 260,000. This decline is bigger than might be expected from the counts that take place at sites covered by WeBS, being larger than the ten-year decline of 14% reported in the last WeBS report. Knot are mobile species within the North Sea and Atlantic Coast wintering area and it is possible that British losses may be explained, at least to some extent, by redistribution.

blog oyc graphThe drop in Oystercatcher numbers from 320,000 to 290,000 appears to be less than 10%, compared to a ten-year decline of 12% on WeBS. Improved analysis of NEWS data helped to add some more birds to the open-coast estimate so the 10% fall may underestimate the seriousness of the Oystercatcher situation. The 25-year Oystercatcher decline on WeBS is 26%, which is not surprising if you look at the changes to breeding numbers in Scotland, where most British birds are to be found. There’s more about this in: From shingle beach to roof-top.

blog RKThe Redshank decline of 26,000 is higher than would be predicted from WeBS figures, suggesting a drop of over 20% since APEP3, rather than ‘just’ 15% for the ten-year WeBS figure. This is a species that also features strongly in the Non-estuarine Waterbird Survey and that might explain the difference. Wintering Redshank are mostly of British and Icelandic origin, with the Breeding Bird Survey (BBS) suggesting a ten-year decline of 24% in our British breeding birds.

The Curlew is now globally recognised as near-threatened. The latest winter estimate is 120,000, down from 140,000 in APEP3. The new total represents between 14% and 19% of the European population, which means that we have a particular responsibility for this much-loved species. Only the Netherlands holds more wintering Curlew than Great Britain. Is the Curlew really nearly-threatened? is one of several blogs about Curlew in the WaderTales catalogue at www.wadertales.wordpress/about .

blog 2 DNIt has been suggested that the long-term declines of Grey Plover and Dunlin  may be associated with short-stopping, with new generations of both species wintering closer to their eastern breeding grounds than used to be the case. WeBS results indicate a 31% drop in Grey Plover and a 42% drop in Dunlin, over the last 25 years. There was a loss of 10,000 for both species between APEP3 and the new review, representing declines of 23% and 3% respectively.

The biggest winners

There are several big winners in the period between APEP3 (2004-09) and the new review (2012-16), although, in some cases, not all is as it seems.

The Avocet has seen further dramatic gains. with the estimated wintering population rising to 8,700. The increase is not quite as big as might have been expected, based on the 43% rise seen in ten years of WeBS counts, but it is still a dramatic continuation of a 40-year trend.

The numbers of Bar-tailed Godwit and Ringed Plover are both substantially higher but at least a proportion of each of these changes is linked to the better coverage and more sophisticated sampling methods that were discussed earlier. Bar-tailed Godwit increases may also reflect redistribution around the North Sea.

blog BW graphOne of the consequences of improved statistical techniques, as used this time around, is the apparent decline in the estimated population of Black-tailed Godwit. The new figure of 39,000 is 4,000 smaller than in APEP3, despite the fact that the WeBS graph clearly shows an increase. Interpolation using WeBs figures suggests that the earlier population estimate should have been 31,000, rather than 43,000.

Sanderling from Greenland spend the non-breeding season as far south as South Africa but  increasing numbers of birds are wintering in Great Britain and Ireland (25% increase in 8 years in GB and 13% in 5 years in Ireland). Interestingly, survival rates of English birds are just as high as those in Namibia. The losers are birds that spend the non-breeding season in equatorial Africa, as you can read here; Travel advice for Sanderling.

There are other winners too, as you can read in the paper. At the start, I posed the question “how many Greenshank are there in the country during the winter?”.  The answer is 810, representing an increase of 200 since APEP3. The vast majority of these wintering Greenshank are birds from the population that breeds in northern Scotland, as you can read in Migration of Scottish Greenshank.

Game species

The estimates for the three wintering waders that are still on the UK quarry list have not changed since APEP3 (published in 2011) as there are no new data available.

Golden Plover: The winter estimate remains as 400,000, as there has been no comprehensive, winter survey since 2006/7. Large numbers of Golden Plover arrive from Scandinavia, Europe and Iceland in the late summer, joining the British birds that choose not to migrate south or west. The GB breeding population is probably less than 50,000 pairs. Most breed in Scotland which has seen a breeding decline of 5% in the period 1995 to 2018 (BBS). Golden Plover is still ‘green listed’.

snipe-headerSnipe (Common): The winter estimate remains as 1,100,000 – a figure that was acknowledged in APEP3 as being less reliable than that of most species. At the same time, the GB breeding population was estimated as 76,000 pairs, indicating at least a 4:1 ratio of foreign to British birds, and that does not take account of the number of British birds that migrate south and west. Snipe are ‘amber listed’ but BBS suggests a recent increase of 26% (1995-2018). There is a WaderTales blog about  Snipe and Jack Snipe.

Woodcock: The winter estimate remains as 1,400,000 – another figure that is not considered to be particularly precise, with much variation between years. The diminishing breeding population is dwarfed by winter numbers, as you can read in this WaderTales blog, with increased attention being given to ways to afford better protection of red-listed, British-breeding birds.

Many of the Golden Plover, Snipe and Woodcock that spend winter in Great Britain are birds that breed in Fennoscandia (Finland, Sweden & Norway). The latest assessment of breeding numbers shows that populations of all three species are stable. See Fennoscandian Wader Factory.

January counts

blog BTThe paper in British Birds also includes a table of January population estimates, to provide data that are comparable to mid-winter counts in other countries. These figures are used in waterbird monitoring for the International Waterbird Census for the African Eurasian Flyway. The main table (and figures mentioned above) are average maximum winter counts (in the period September to March). Black-tailed Godwit is one species that illustrates the difference, with a mean of 30,000 in January and a mean peak count of 39,000. Having moulted in Great Britain, some Black-tailed Godwits move south to France and Portugal in late autumn, returning as early as February. January counts are therefore substantially lower than early-winter and late-winter counts. There is more about the migratory strategy employed by Black-tailed Godwits that winter in southern Europe in Overtaking on Migration.

Looking forward

blog BB coverThe authors have done a tremendous job. They have refined the way that estimates are calculated, they have combined the results from WeBS and NEWS III, and they have delivered population estimates for 25 wader species and many more other species of waterbirds. These population estimates will be used in conservation decision-making until the next set of numbers becomes available. Meanwhile, thousands of birdwatchers will count the birds on their WeBS patches in each winter month, every year. Without them, this paper could not have been written.

Before the next assessment, there will need to be another NEWS survey, to check up on species that use rocky and sandy shore birds, such as Purple Sandpipers, Turnstone and Curlew. Hopefully, there will also be a dedicated survey to assess Lapwing and Golden Plover numbers and perhaps we might find a way to refine the old estimates for Woodcock, Snipe and Jack Snipe.

Paper

Population estimates of wintering waterbirds in Great Britain. Teresa Frost, Graham Austin, Richard Hearn, Stephen McAvoy, Anna Robinson, David Stroud, Ian Woodward and Simon Wotton. Published in British Birds Volume 112. March 2019.

blog flying godwits


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

Why is spring migration getting earlier?

In Iceland, young trend-setting Black-tailed Godwits are changing the timing of spring migration

Flocks of up to 5000 Black-tailed Godwits gather in Alftafjordur in spring: Tómas Gunnarsson

Flocks of up to 5000 Black-tailed Godwits arrive in Alftafjordur (East Iceland) in spring: Tómas Gunnarsson

In recent years, earlier arrival of spring migrants has been widely reported in birds as diverse as swallows and waders but it’s not a universal trend; species such as British Cuckoos and Icelandic Whimbrels have not changed their arrival dates.  Interestingly, many of the species that have not advanced timing tend to be those that are declining.  By thinking about the mechanisms that enable some species to take advantage of earlier spring warming it might be possible to explain how timings and population changes may be linked.

Are individual Black-tailed Godwits arriving earlier each spring? (Photo: Nigel Clark)

Are individual Black-tailed Godwits arriving earlier each spring? (Photo: Nigel Clark)

The simplest way for spring migration to advance would be for individual birds to change their arrival dates, arriving earlier now (either because they have departed earlier or migrated faster) than they did in previous years.  These changes could be facilitated by changes to weather conditions before, during or after migration.  In general, the arrival of short-distance migrant species has advanced more than long-distance species, which has led to suggestions that individual birds are able to assess conditions on their breeding grounds from afar, and to ‘fine-tune’ arrival accordingly. This could explain why long-distance migrants seem less well able to change their schedules than species which have less far to travel.

Figure 1: Changes in first spring arrival dates of six species of waders in southern Iceland from 1988 to 2009 (reproduced from Gunnarsson & Tómasson 2011)

Figure 1: Changes in first spring arrival dates of six species of waders in southern Iceland from 1988 to 2009 (reproduced from Gunnarsson & Tómasson 2011)

This pattern of advances in arrival dates, and greater advances in short-distance migrants is seen in birds arriving into Iceland each spring (Gunnarsson & Tómasson).   By monitoring the first dates of a range of migratory breeding species to the area around Laugarás, an inland village in southern Iceland, over the period 1988 to 2009, Tómas Gunnarson and Gunnar Tómasson showed that species which spend the winter further south than France showed no change in arrival, whilst those from further north in Europe were returning earlier.  The southern group included the only wader in the Gunnarsson & Tómasson study which uses this migration strategy, Whimbrel (see diagram).

GL-YX on a windy day in western Iceland. He has been seen in eleven years. Despite the vagaries of spring weather, his arrival dates have only been spread over nine days (standard deviation 3.5 days) and have not advanced over the period 2003-2015

GL-YX on a windy day in western Iceland. He has been seen in eleven years. Despite the vagaries of spring weather, his arrival dates have only been spread over nine days (standard deviation 3.5 days) and have not advanced over the period 2003-2015

One of the species that has advanced spring arrival (by about two weeks in the last two decades) is the Black-tailed godwit.  Since 2000, we have been recording arrival dates of individually colour-ringed godwits into coastal Iceland – giving us the opportunity to assess whether individuals have indeed brought forward their time of arrival.  By making regular visits to the same sites we have discovered that the dates when we first come across individuals are remarkably consistent.  Although the arrival of the whole population is spread over a five or six week period, the window in which a specific Black-tailed Godwit appears is generally predictable, whether he or she is a bird that we tend to first see in mid-April or mid-May.  There are annual differences, of course, which appear to be linked to periods of adverse weather during the period of the sea-crossing (Gunnarsson et al 2006), from departure points in The Netherlands, The UK Ireland, France and Portugal, but there is no significant trend.

Dates of spring arrival into Iceland of 54 individually marked black-tailed godwits recorded on arrival in between 4 and 8 years, from 1999 to 2012 (reproduced from Gill et al. 2014). Whether an individual arrives early (left-hand birds) or late (right), the sighting dates for each bird are highly consistent.

Dates of spring arrival into Iceland of 54 individually marked black-tailed godwits recorded on arrival in between 4 and 8 years, from 1999 to 2012 (reproduced from Gill et al. 2014). Whether an individual arrives early (left-hand birds) or late (right), the sighting dates for each bird are highly consistent.

timing pop v indivAlthough the arrival date for the population has been advancing at ~0.8 days per year (Gunnarsson & Tómasson 2011), there has been no trend in individual arrival dates (not significantly different to zero days per year); Gill et al. 2014.

Most of the godwit chicks were ringed by groups of volunteers led by Pete Potts and Ruth Croger (Photo: Tómas Gunnarsson)

Most of the Black-tailed Godwit chicks were ringed by groups of volunteers led by Pete Potts and Ruth Croger (Photo: Tómas Gunnarsson)

If individuals are consistent in arrival but the population is advancing, the advance must presumably result from new birds recruiting into the population being earlier-arrivers than recruits from previous years?  Fortunately, there is a second long-running set of data that’s available to answer this question, in a large part because of the efforts of Pete Potts and Ruth Croger of Farlington Ringing Group.  In the period 1999 to 2014, they organised teams of volunteers to ring Black-tailed Godwit chicks in Iceland, with the support of the Icelandic Natural History Museum.  Significant contributions to the total of over 350 colour-ringed chicks were also made by Tómas Gunnarsson and José Alves, while researching the breeding ecology of Black-tailed Godwits for the Universities of East Anglia and Iceland.

Dates of spring arrival into Iceland of 46 individuals hatched in different years and subsequently recorded on spring arrival (reproduced from Gill et al. 2014)

Dates of spring arrival into Iceland of 46 individuals hatched in different years and subsequently recorded on spring arrival (reproduced from Gill et al. 2014)

Wader chick mortality is quite high and there are further losses in the eighteen-month period between autumn departure from Iceland and the first return trip, eighteen months later, so it was wonderful to have a sufficiently big cohort of marked recruits to look at patterns and trends.  For this study, arrival dates for 46 individuals of known hatch year were available for analysis.  As can be seen from the graph, arrival dates of new recruits have been getting earlier, with birds hatched in the last decade arrive around two weeks earlier than individuals hatched in the 1990s.

There are several reasons why recent recruits may be arriving earlier than in previous years, but the most likely is that this is a knock-on effect of advances in godwit laying dates that have occurred in recent decades.  Icelandic godwits nest earlier in warmer springs, and the frequency of warmer springs has increased.  Early fledging may benefit new recruits, by increasing the time available for them to migrate south, locate a good winter site and be in condition to return early when they recruit into the breeding population (Alves et al. 2013 http://www.esajournals.org/doi/abs/10.1890/12-0737.1  http://dx.doi.org/10.1890/12-0737.1). As their arrival date will be consistent thereafter, the overall timing of arrival of the population will advance.

Will this young Black-tailed Godwit contribute to our understanding of the timing of migration? (Photo: Tómas Gunnarsson)

Will this young Black-tailed Godwit contribute to our understanding of the changing timing of migration? (Photo: Tómas Gunnarsson)

Many other studies of different species in which individuals are tracked during migration are showing similar levels of consistency in individual timing of migration.  What then is causing the variation among species in rates of advance?  Long-distance migrants typically arrive later on the breeding grounds and breed quite soon after arrival, while short-distance migrants can have quite large time gaps between arrival and laying, depending on conditions for breeding. Short-distance migrants therefore have more capacity to advance laying dates (because they are on the breeding grounds waiting for suitable conditions), while long-distance migrants, such as Whimbrels in Iceland, arrive later and so cannot breed earlier even in a warmer year. Advances in spring arrival dates may therefore result from advances in laying dates and associated benefits of early fledging for recruits, and lack of advance in long-distance migrants may be a consequence of arriving late and hence being unable to take advantage of early, warm spring conditions.

In the Icelandic subspecies of Black-tailed Godwit, which is expanding in both number and distribution, it is clear that young recruits to the breeding population are driving the advance in timing of migration.  We only know this because of the long-term programme of chick ringing by volunteers and because we have been able to record the timing of individual birds’ migratory activities over a large number of years.  Funding for this work has been provided by the volunteers themselves, NERC , Icelandic Research Council  and EU TMR.

This blog is based upon research presented in the following open access paper:

Gill, J.A., Alves, J.A., Sutherland, W.J., Appleton, G.F., Potts, P.M. & Gunnarsson, T.G. 2013 Why is timing of bird migration advancing when individuals are not? Proceedings of the Royal Society B. , 281, 20132161

Please send reports of colour-ringed Black-tailed Godwits to Jenny Gill (j.gill@uea.ac.uk). She will reply with full details of any birds ringed on the Wash or forward your e-mail to colleagues running other schemes.


 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

Is the Curlew really ‘near-threatened’?

If a Curlew can live for over 32 years and there are flocks of 1000 in Norfolk, how can they be described as near-threatened? 

Dark times lie ahead for Curlew? (© Graham Catley)

Dark times lie ahead for Curlew? (© Graham Catley)

Thirty years ago there were eight members of the world-wide curlew family but now we may well be down to six.  The planet has lost one species, the Eskimo Curlew, with no verified sightings since the 1980s, and probably the Slender-billed Curlew as well.  Of the others, Far Eastern Curlew and Bristle-thighed Curlew are deemed to be endangered and vulnerable, respectively, and our own Curlews are classed as near-threatened, which is the next level of concern. This may seem strange, especially when flocks of 1000 can be seen on the Norfolk coast.  However, evidence suggests that we should take heed of what is happening to other members of the curlew family, as we consider the future of this evocative species with its wonderful bubbling curl-ew calls.

Threat levels for the eight members of the Curlew family (based on IUCN BirdLife assessments)

Threat levels for the eight members of the Curlew family (based on IUCN/BirdLife assessments)

Our Curlew – more properly called the Eurasian Curlew – was until relatively recently a locally popular game species in Britain, especially in September and October, when birds are reputed to be particularly flavoursome.  A male Curlew is equivalent in weight to a Wigeon (or two Teal) and the bigger female may well be as heavy as a Mallard, so it is not surprising that they were worth targeting.  They came off the British quarry list in 1981.

Map showing movements of ringed curlews. Purple dots indicate where British/Irish ringed birds have been recovered and orange dots show ringing sites of birds found here and wearing foreign rings. Maps of movements can be found on the BTO website at http://www.bto.org/volunteer-surveys/ringing/publications/online-ringing-reports

Purple dots indicate where British/Irish ringed Curlews have been recovered and orange dots show ringing sites of birds found here and wearing foreign rings. Maps of movements can be found at http://www.bto.org/volunteer-surveys/ringing/publications/online-ringing-reports

The Curlews that we see on the Norfolk coast in autumn and winter are drawn from a wide breeding area; some are of British origin but many are from Scandinavia, Finland and Russia.  The Wash Wader Ringing Group recently received a report of a bird that was ringed in Norfolk in September 2000 and recovered in Izhma in Russia in May 2014.  At 3300 km (2000 miles) this is nearly as far away as the furthest east dot on the map of Curlew recoveries, shown here and published on the website of the British Trust for Ornithology.  The bird was an adult when ringed so must have been at least 15 years old when shot.  This seems like a good age for a Curlew but is less than half of the British longevity record, set by a chick ringed in Lancashire in 1978 and found dead on the Wirral in 2011.

Curlew mortality is higher in severe winters (© Graham Catley)

Curlew mortality is higher in severe winters (© Graham Catley)

Curlew numbers on the Wash, which sits between the counties of Norfolk and Lincolnshire, increased dramatically when shooting ceased in 1981, although milder winters could have also have been influential.  In the five years immediately before the ban, the average maximum, winter Wetland Bird Survey count on the Wash was 3281, rising to 9642 in the period 2006/07 to 2010/11.  There were similar increases on the North Norfolk coast and a bit further south at Breydon Water.  The broader, national picture is one of increase between 1981 and 2001, although generally at a lower level to that seen in Norfolk, followed by a steady, shallow decline.  If numbers are higher than they once were does this mean that we should be less concerned about Curlews – and what is the justification of the species’ near-threatened designation?

Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Conserving migratory species is difficult because individuals rely on different resources in different countries at different stages of the year.  For Curlews, there is evidence that breeding season problems are at the heart of large decreases in numbers in Russia, through the Baltic and into The Netherlands – the countries from which much of the wintering population on the east coast is drawn.  According to the European Commission’s species management plan, drivers of decline include wide-scale intensification of grassland management for milk production, land-abandonment and increased predation in some areas.  Autumn, winter and spring hunting is thought to have had a lesser but contributory effect to the long-term losses, with hunters across the European Community shooting between 3% and 4% of the population each year.  In the last twenty years, within the EC, hunting of Curlew has been confined to Ireland, Northern Ireland and France.  Much of this shooting pressure was and is in France, where coastal hunting of Curlew was reinstated after a five year moratorium. Read blog about this here.

curlew webpageFocusing on Britain and Ireland, we have seen major losses in our breeding populations.  In Ireland, the Curlew population is estimated to have dropped from 5000 to 200 pairs in the twenty years between 1991 and 2011 (with further declines since – see Ireland’s Curlew Crisis blog below). There has been an 80% decline in Wales and other losses elsewhere.  There’s more about these distributional changes in a 2012 article written for the BTO website.

Curlew productivity in several areas appears to be very low and it is possible that the adults we are seeing are part of an ageing population.  As has been shown in seabirds, counts of adults can give a false sense of security, as it is easy not to notice that there is little recruitment of new, breeding adults into the population, with obvious long-term consequences.

Graph shows the changing Curlew population in Great Britain (Wetland Bird Survey)

Graph shows the changing Curlew population in Great Britain (Wetland Bird Survey)

The decline in the number of breeding Curlew in Great Britain is clearly reflected in monthly, winter counts undertaken by volunteers on west coast estuaries.  On the Dee, for instance, the average peak-winter count dropped from 6109 in the early 1970s to 4348 in the five years after the shooting ban, rose to 5081 in the late 1990s but then slipped back to 3802.

In Ireland and Northern Ireland, a total ban on shooting Curlew was announced in 2012, brought in once it was clear that the estimated November harvest of between 6% and 8% was unsustainable and set against a background of the collapse of the local breeding populations.  The same local reasoning lies behind continuing protection in Wales, western England and in much of Scotland, especially at a time when financial support to land-managers is being used to try to bolster British breeding numbers.  In eastern England, Curlew conservation has a more international flavour, as we provide a safe haven for birds from as far away as Russia.

With relatively few continental birds, the Wetland Bird Survey trend reflects more local declines

With relatively few continental birds in Northern Ireland, the Wetland Bird Survey trends probably reflect local declines

Britain & Ireland, between them, provide winter homes for half of the Europe-wide population of Curlews (about 210,000 out of 420,000), with the Netherlands holding 140,000 birds.  There are also significant flocks in Germany and about 20,000 in France.  These may seem like reasonable numbers but, given that fewer chicks are being raised, the number of adults is declining, two close relatives have been driven to extinction and other curlew species are in trouble, the label of near-threatened seems highly appropriate.

We should be proud of our wintering Curlews in Great Britain, where numbers have stabilised, albeit at a level that is 20% lower than at the turn of the century, but there is no room for complacency in Northern Ireland, where the decline continues.

Update: Curlew was added to the red list of the UK’s Birds of Conservation Concern on 3 December 2015

Other WaderTales blogs about Curlew

  • Why are we losing our large waders? takes a look at a review of the common threats faced by the 13 Numeniini species (godwits, curlews and Upland Sandpiper).
  • Curlews can’t wait for a treatment plan focuses on the primary drivers of the species’ breeding decline in Great Britain.
  • Sheep numbers and Welsh Curlew looks at habitat associations within a large site  in the Welsh uplands; getting the grazing regime right seems to be very important.
  • Curlew Moon has at its heart a review of Mary Colwell’s book of the same name but also summarises some of the issues being faced by Curlew in Ireland and the UK.
  • Ireland’s Curlew Crisis focuses on the nationwide breeding survey between 2015 and 2017, which revealed a 96% decline in the number of pairs in just 30 years.
  • Curlews and foxes in East Anglia suggest that ‘curlew plots’ may be helpful in the fight to conserve the species.

On autumn high tides, flocks of Curlew roost on east coast stubble fields (© Graham Catley)

On an autumn high tide, a flock of Curlew roosts on an east coast stubble field (© Graham Catley)


 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

UK Dotterel numbers have fallen by 57%

Research from RSPB Centre for Conservation Science, with University of Aberdeen (School of Biological Sceinces), Scottish Natural Heritage (SNH) and Natural Research Ltd

Male Dotterel brooding chicks: Alistair Baxter

Male Dotterel brooding chicks: Alistair Baxter

I have only once climbed a mountain to count Dotterel, with Phil Whitfield decades ago, but that is enough to appreciate how many hundreds of hours of hard work lie behind the statement, “The number of Dotterel breeding in the UK declined by over half between 1987/88 and 2011”. This is the headline in a paper published in the November 2015 issue of the BTO journal, Bird Study:

Changes in the abundance and distribution of a montane specialist bird, the Dotterel Charadrius morinellus, in the UK over 25 years. Daniel B Hayhow, Steven R Ewing, Alistair Baxter, Andy Douse, Andrew Stanbury, D Philip Whitfield & Mark A Eaton Bird Study 62:4, 443-456

As Des Thompson and Phil Whitfield wrote at the conclusion of their account for the 1988-91 Breeding Atlas, “The Arctic affinities of the British Dotterel, its beauty, its rarity and its likely sensitivity to habitat and climate change secure its place as one of our most fascinating breeding birds”.  Well-documented stories of females laying clutches in Scotland, to be brooded by their male partners, and then flying on to Norway to lay second clutches add an air of mystery too.

The 2011 Dotterel Survey was carried out under the Statutory Conservation Agencies/RSPB Annual Breeding Bird Survey (SCARABBS) programme and was funded by the RSPB and SNH (Alistair Baxter)

The 2011 Dotterel Survey was carried out under the Statutory Conservation Agencies/RSPB Annual Breeding Bird Survey (SCARABBS) programme and was funded by the RSPB and SNH (Photo: Alistair Baxter)

The population estimate of 423 breeding male Dotterel in 2011 represents a decline of 43% since 1999, when the comparable total was 747 pairs, and of 57% since 1987/1988 (981 pairs).  All regions except the West Highlands had lower numbers in 2011 than in 1999, with the core area of the East Highlands (the Grampians east of the A9) experiencing a significant decrease of 32% since 1999 and 56% since 1987.  This massif has become increasingly important, with 60% of the pairs in what amounts to 30% of the potential breeding habitat for Scottish Dotterel.

No Dotterel were recorded outwith Scotland during the systematic national survey but Bird Atlas 2007-11 fieldwork did add a record from Northern England.  In the absence of annual monitoring, a national survey can only provide a snapshot for a species.  However, information gathered during the four summers of the Bird Atlas project and as part of an ongoing detailed study suggests that the results for 2011 are representative of the current UK Dotterel population – and that the declines are therefore very much real.

Population changes across the range

Large-scale surveys of Dotterel are difficult, due to the remoteness of many of their breeding sites, and monitoring elsewhere across their European breeding range tends to be based on visits to particular sites or using transects.  Given the plasticity shown by the females – including an ability to nest in two countries in one year – changes in apparent numbers could potentially reflect the fact that birds breed further north in some springs than in others.  The best series of data come from Swedish Lapland, where Svensson & Anderson reported no changes in the population over the period 1972 to 2011.

In, Finland, Pulliainen & Saari observed that most females left their study area after egg-laying and hypothesised that this was in order to secure more mates further north. Lucker et al. have found evidence for higher rates of shared incubation by females at the more northern extent of the species’ breeding range than those breeding further south, providing some evidence to support this hypothesis.  Saari had previously estimated the Finnish population to be 90% less than in the early 1900s and suggested that hunting in early 20th century and overgrazing by reindeer may have been to blame.   Since the 1960s, the tree line has advanced and large areas of the mountain heath are now covered by scattered Scots Pines, making the habitat largely unsuitable for Dotterel.  Similar processes, associated with warmer conditions, could have major, negative impacts the number of Dotterel breeding in Scotland.

Is the SPA network working for Dotterel in Scotland?

Racomotrium heath is an important and increasingly rare habitat (Alistair Baxter)

Racomotrium heath is an important and increasingly rare habitat (Alistair Baxter)

The designation of Special Protected Areas (SPA), based on the results of the 1987/88 survey has been a key tool in the efforts to conserve Dotterels in Scotland.  This network of montane sites has helped to provide a focus for research funding and planning considerations.  Encouragingly, SPAs have supported between 50% and 60% of the population since designation.

The decline in numbers of Dotterel within and outwith the SPA network is of concern, but in terms of site occupancy, sites in SPA/SSSIs were more likely to be occupied than those outside the protected area network.  Protected area designation has been shown to be good for a group of northern species at the trailing edge of their distribution in the UK, although this effect decreased at higher latitudes and altitudes (Gillingham et al. 2015).

Explaining the declines

The well-referenced, discussion section of the paper looks at the potential reasons for the changes to Dotterel populations and assesses the available evidence.

Habitat change in the high mountains: Racomitrium moss heath has been shown to provide important foraging opportunities for Dotterel of all ages; this is a habitat that has been in a long-term decline over the last half century.   Studies have outlined how overgrazing and levels of atmospheric nitrogen interact, resulting in changes to the composition and extent of montane heaths.

A frequent prey of both adult and juvenile Dotterel is Tipulid (cranefly) larvae which require dense mats of moss vegetation.  Changes in composition and extent of Racomitrium heath could result in reduced prey availability, potentially affecting settlement decisions and breeding success for Dotterel.

Raven abundance has increased across much of the Dotterel's range (Map from Bird Atlas 2007–11, which is a joint project between BTO, BirdWatch Ireland and the Scottish Ornithologists’ Club)

Raven abundance has increased across much of the Dotterel’s range (Map from Bird Atlas 2007–11, which is a joint project between BTO, BirdWatch Ireland and the Scottish Ornithologists’ Club)

Predation in the breeding season: Predation of Dotterel eggs by Ravens can cause localised declines, and lower return rates have been reported for adult male Dotterel after clutch loss by predation. The period of decline in Dotterel is coincident with an increase in range and abundance, of Ravens in Scotland.  Although previous work has found no significant negative associations between Raven numbers and upland wader populations, this interaction may well warrant further investigation.

Disturbance: There is little strong evidence for widespread effects of increased visitor numbers, despite negative impacts of such activities on heath condition.

Pressures in wintering areas: Pesticide use and hunting on the wintering grounds, North Africa and Spain, have been suggested as possible factors in the decline.

More attractive conditions further north: Upland species, such as Dotterel, are cold-adapted and may well find northerly areas more conducive to breeding.  Without a flyway approach to Dotterel monitoring it is not possible to distinguish between a northerly shift in the breeding area of Dotterel and population-scale declines.

What next?

The 2011 Dotterel survey clearly shows the decline in numbers of Dotterel breeding in the UK and contraction to core sites in the East and Central Highlands.  Further, detailed work is required to understand the mechanisms driving the observed population trends, which may well involve studies in wintering areas and migration hot-spots, as well as a mixture of ecological research and ongoing monitoring in the mountains of Scotland.

The 2011 Dotterel survey has provided a spring-board for detailed research by Alistair Baxter, which is being written up as part of his PhD at the University of Aberdeen.  By repeating studies carried out during the 1980s by SNH, he hopes to see whether changes in habitat availability, habitat quality and invertebrate abundance can help to explain the decline in numbers in the last thirty or so years.

Ptarmigan is another montane species that will be targeted by

Ptarmigan is a key montane species that is being targeted by “What’s Up?” (Alistair Baxter)

Given how much effort has to go into any survey of upland species and the relative infrequency of national surveys, it is great that two recent initiatives are making the most of the calories burned to climb our highest peaks.  Many volunteers involved in the annual Breeding Bird Survey of upland squares now add an adjacent square to the original, randomly-selected plots, in order to increase the sample size in these sparsely populated but special bird areas.  Another valuable contribution is being made by mountain-lovers who know their birds and who are now contributing to the BTO Scotland led “What’s Up?” project.  This focuses on species that are sensitive to climate change and disturbance, such as Ptarmigan, Snow Bunting and Dotterel.

In an era of ever tightening budgets, it is unclear when it might be possible to organise another national survey for Dotterel.  Let’s hope that, until then, “What’s Up?” can help to alert us to distribution changes and that annual surveys of key sites might provide indications of national population changes. 

Dotterel was moved onto the red list of species of conservation concern on 3 December 2015.


 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

Conserving British-breeding Woodcock

To help to take the pressure off declining and now red-listed British-breeding Woodcock, many estates are already delaying the start of the Woodcock shooting season.  How might this make a difference?

This is a modified version of an article published in Shooting Times on 30 Sep 2015. There are updates at the end, reflecting changing advice provided by the Game & Wildlife Conservation Trust.

Photo: Richard Chandler

Photo: Richard Chandler

Each autumn, the British population of Woodcocks is swamped by the arrival of up to a million birds, returning from northern Europe and Scandinavia. The exact timing of their migration is very much influenced by weather, with birds crossing the North Sea as early as October or as late as December.  The numbers each year are thought to vary markedly, reflecting peaks and troughs in the size of the European breeding population, annual chick production, the amount of frost and snow on the other side of the North Sea and the timing of periods of cold weather.

A quick look at the bag index for Woodcock, produced by the Game & Wildlife Conservation Trust (GWCT), shows annual variation in the numbers shot each winter but no downwards trend.  Hunting appears to be sustainable (but see note at the bottom giving advice from GWCT about shooting in winter of 2017/18).  Unfortunately, there is a problem; British-breeding Woodcock are in serious decline and there is no way to differentiate between a local bird and one from continental Europe.  As the GWCT Woodcock tracking project has shown, birds share the same woodland habitats during winter months.  Mara and Jack, for instance, two birds caught in March 2014 on Islay, have very different annual stories to tell, with Mara breeding locally and Jack migrating to Russia.

A shrinking distribution

Bird Atlas 2007-11, published by the British Trust for Ornithology (BTO), confirmed that our Woodcock are in trouble.  Between 1968-72 and 1988-91, the number of 10×10 km atlas squares where Woodcock were present fell from 1439 to 917, representing a decline of 36%.  By 2008-11, the number was down to 632, a further drop of 31%.  In the 1968-72 Atlas, Woodcocks were generally widespread, with birds absent only from parts of southwest England and Wales and easy to find from the North Midlands through to northern Scotland, other than in the highest mountains.  Fragmentation that was becoming apparent in 1988-91 was glaringly obvious in 2008-11, especially in the south and west.  In Ireland the situation, if anything, looked worse.

Bird Atlas 2007-11, published by the BTO, in association with the Scottish Ornithologists’ Club and BirdWatch Ireland, shows that breeding Woodcock are disappearing from southern and western Britain, as well as from Ireland. Downwards pointing black arrows show losses, with bigger symbols indicating recent changes.

Bird Atlas 2007-11, published by the BTO, in association with the Scottish Ornithologists’ Club and BirdWatch Ireland, shows that breeding Woodcock are disappearing from southern and western Britain, as well as from Ireland. Downwards pointing black arrows show losses.

Early results being contributed to the Bird Atlas 2007-11 project confirmed that there was an urgent need for a special Woodcock survey, to try to assess numbers as well as distribution, and this was organised for the summer of 2013.  The GWCT and the BTO wanted to replicate the survey they had organised in 2003, which suggested that the breeding population across Scotland, Wales and England included just over 78,000 territorial males.

Andrew Hoodless of GWCT has shown that the number of Woodcocks observed during a standard evening watch period provides a good index of local abundance.  The national survey called for the deployment of hundreds of birdwatchers, who were asked to visit chosen sites, many of which had been visited ten years previously.  Standing at dusk and listening to the distinctive roding calls of male Woodcocks, as they patrol the boundaries of their territories, provides magical moments for lucky birdwatchers.  However, the chance of success in many parts of the country was far lower in 2013 than it had been in 2003.  A paper, with a full regional analysis was published in 2015, revealing an estimated fall in numbers of 30%, to just over 55,000 roding males.  As suggested by the Atlas distribution maps, percentage losses were higher in Wales and England than in Scotland.

Current status and recent trend of the Eurasian Woodcock Scolopax rusticola as a breeding bird in Britain, by Christopher J Heward, Andrew N Hoodless, Greg J Conway, Simon Gillings & Robert J Fuller, in Bird Study Nov 2015

The main aim of the 2013 Woodcock survey was to assess the population, rather than to understand the causes of decline, but it is interesting to note that there were smaller losses in the largest areas of woodland.  More detailed studies have suggested that larger woods may offer a greater diversity of habitats and damper micro-climates in which to feed.  Booming deer populations are having major effects on a lot of woodlands; by browsing the vegetation they can open up the understorey, thereby removing nesting habitat and drying out soils.  There are probably several factors driving down the breeding population and it has been suggested that recreational disturbance and over-winter hunting of resident birds could each be playing a part in declines.

Changes to the hunting season?

BirdTrack is coordinated by the BTO, in partnership with RSPB, BirdWatch Ireland, the Scottish Ornithologists’ Club and the Welsh Ornithological Society. These lists provide fascinating information about the timing of migration, annual breeding patterns and species’ abundance. See www.birdtrack.net to learn more.

BirdTrack is coordinated by the BTO, in partnership with RSPB, BirdWatch Ireland, the Scottish Ornithologists’ Club and the Welsh Ornithological Society. These lists provide fascinating information about the timing of migration, annual breeding patterns and species’ abundance. See www.birdtrack.net to learn more.

Although the main pressures may well occur during the summer months, one way to help British breeding Woodcock may be to change the start of the shooting season.  The season currently opens on 1 September in Scotland and 1 October across the rest of the UK.

Looking at BirdTrack data, collected from species lists sent in by thousands of birdwatchers across Britain & Ireland, it is clear that there are virtually no continental Woodcock in these islands during September and few until at least the second half of October.  In the graph alongside, the red line shows average rates of occurrence on birdwatchers’ lists.  The blue line for 2014 indicated a pulse of arrivals in early October, largely as observed by birdwatchers on the east coast.  These birds will have moved inland and disappeared into woodland and farmland.  The main arrival in this particular year appears to have been in late October with later spikes in the graph suggesting further bursts of east coast activity in November and December.

The 2013 Woodcock survey was funded by the Game & Wildlife Conservation Trust, the Shooting Times Woodcock Club and a charitable trust. Photo: Richard Chandler

The 2013 Woodcock survey was funded by the Game & Wildlife Conservation Trust, the Shooting Times Woodcock Club and a charitable trust. Photo: Richard Chandler

The BirdTrack pattern will come as little surprise to gamekeepers and shoot-owners, many of whom already restrict Woodcock shooting to the winter months, in order to minimise losses of local, resident birds.  GWCT scientists have been encouraging restraint in the autumn months for some while.  Now, having analysed the results of the GWCT/BTO 2013 Woodcock survey, and shown a further decline of nearly a third in just ten years, they are researching the potential impact of shooting on resident birds. This will include an assessment of whether a formal change to the timing of the hunting season for Woodcock is required, in order to add an extra level of protection to resident birds.

Update: 28 July 2017

New GWCT  guidance: ‘generally we recommend not shooting woodcock before 1 December’ and not at all if ‘numbers have been low in the area’. More information is available at https://www.gwct.org.uk/media/696047/Pocket-woodcock-guide.pdf

Update: 11 December 2017

Migrant Woodcock appear to have had a poor breeding season and GWCT is advising restraint:

Dr Hoodless has issued the following statement: “GWCT and the Woodcock Network are advising shooters across the UK to rethink their woodcock shooting for this season and reduce their bags. This echoes moves being taken by organisations in several other European countries. A further update will be issued in early January, once more information is available.”

“Although similar events will have happened many times in the past, this is the first time that monitoring of woodcock age ratios by ringers, and improved communication across Europe, has been able to offer shooters an early warning system. Populations normally rebound after such events, but most shooters understand the importance of preserving breeding stocks when there are signs of adverse natural events and are prepared to minimize shooting pressure in order to aid population recovery.”

Read more here

Update: 16 March 2018

Woodcocks are severely affected by cold weather. Research by GWCT suggest that Woodcock start to suffer when the ground has been frozen for relatively short periods of time. They propose restraint after four days of freezing conditions, with birds being given a recovery period of seven days once a thaw commences. There’s more in this blog here and the paper can be found here.

Update: September 2020

There is no suggestion that the numbers of Woodcock breeding in Finland, Sweden and Norway are changing. This blog summarises survey data for breeding waders during the period 2006 to 2018.


 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

A helping hand for Lapwings

This article has been slightly adapted from one written for the Autumn 2015 edition of The Harrier, published by the Suffolk Ornithologists’ Group

Lapwing in flight: Richard Chandler

Lapwing in flight: Richard Chandler

The space-invader cries of displaying Lapwings are welcome signs of spring across much of Britain’s countryside and losses of this iconic species, especially in lowland England, have been well chronicled.  Conservation organisations, and the RSPB in particular, are successfully supporting breeding numbers on nature reserves but how can their interventions be replicated on working farms, without flooding fields and installing fox-proof electric fences?

On the look-out: Grahame Madge/RSPB impages

On the look-out: Grahame Madge/RSPB impages

Dr Jen Smart of the RSPB Centre for Conservation Science and Professor Jenny  Gill of the University of East Anglia have been studying breeding waders on  RSPB Reserves in the Norfolk Broads for over ten years, but more recently they have extended their wader research into commercially managed grasslands across Norfolk and Suffolk, using funding from Defra.  At the February 2015 ‘Foxycology’ conference, Dr Smart explained how the RSPB is trying to manage the conflict between the conservation of ground-nesting birds and foxes.  The RSPB does not rule out shooting as a protection measure – there’s active fox control in the study site – but prefers to adopt non-lethal solutions to the predation problem.  One answer may be to provide foxes with ‘convenience food’, in the form of mice and voles.  If it’s easier to find mice and voles than wader nests and chicks then perhaps that’s what foxes will do?

Predation is a natural process but rates can be severely skewed by the way that the countryside is managed, especially when the balance of predator and prey is disturbed.  Many predators are opportunists, with species such as foxes, crows, gulls and raptors switching their activities to take advantage of local food availability.  Seasonal abundance of food resources can affect both survival and productivity.  An inexperienced young fox must have a better chance of surviving the winter if he is presented with a generous supply of released pheasants, whilst a vixen, trying to raise a litter of cubs, will find easy pickings in a gull colony.  In the same way, a nature reserve that is full of nesting waders will often attract foxes during the breeding season.

By creating shallow ditches, which add water and insects to grassland habitats, Lapwing productivity is increased: Mike Page/RSPB

By creating shallow ditches, which add water and insects to grassland habitats, Lapwing productivity is increased: Mike Page/RSPB

The RSPB has become very good at increasing populations of wading birds breeding on their lowland nature reserves but staff are frequently frustrated by the low numbers of young birds that survive through to fledging in some years.  Adding water to the landscape, in the form of pools and ditches, attracts high densities of breeding waders, as these wet features provide insect-rich places to which adults can take their chicks.  The RSPB/UEA research team has found that Lapwing nests are far more successful when birds nest at high densities, presumably because they work together to look out for and drive off potential predators, and they also found that Redshanks benefit from the activities of the more numerous and defensive Lapwings.  Practical actions, such as clearing woodland that abuts wetland or removing single trees in which crows sit to spot the next meal, have been shown to reduce avian predation in the daytime, to such an extent, in fact, that three-quarters of nest-losses are now taking place at night.

Lapwing chick: Richard Chandler

A young and vulnerable Lapwing chick: Richard Chandler

Using cameras, the team has shown that 70% of the culprits filmed taking eggs are foxes, with badgers coming a distant second, at 12%.  Wader chicks leave the nest soon after hatching, and RSPB research has shown that chick predation is then largely from foxes at night and raptors in the daytime, but with stoats, weasels and opportunistic birds, such as grey herons, taking smaller numbers.  Overall, by far the biggest threat to productivity is the fox.

One fox (and badger) deterrent that is available on nature reserves is to use well-maintained mains-supplied electric fences to surround fields in which waders nest.  Trials by the RSPB have shown that Lapwing fledging success is significantly improved in fenced areas, increasing from just over 0.2 chicks per pair to 0.8 chicks.  The target level for a sustainable population is 0.6 young per pair so the lower figure is well below par and 0.8 should be providing a surplus of birds that can go on to nest elsewhere.  Fences are not perfect, however; they do not exclude predators such as stoats and weasels, and the increased success of nests means high densities of chicks can be an irresistible resource for opportunistic and adaptable aerial predators trying to feed their own young.  Fencing is also only really effective on a relatively small scale so does not provide the solution to what is a landscape-scale problem.  RSPB research has shown that there is a lot of variability in predation rates, which provides opportunities to try to understand the complex interactions between foxes, mustelids (stoats and weasels), small mammals and waders.

In open grassland, Lapwings can keep an eye out for approaching predators: Richard Chandler

In open grassland, Lapwings can keep an eye out for approaching predators: Richard Chandler

Much of the patchiness of productivity within a site is linked to the amount of grass in fields and along field edges.  Grazing is a key management tool in wet grasslands, with cattle creating the short and varied sward structure that is attractive to a range of breeding waders.  By using ink tracking tunnels, within which mammals leave their footprints, and looking for field-signs of activity, Dr Becky Laidlaw has been able to show that this short grass is of little use to mice and voles.  She discovered that they prefer verge areas, outside the fields, where the grass is at least 20 cm tall and where there is ground-level vegetation cover of more than 80%.  Using data on wader nest success collected over 10 years, she was also able to show that Lapwings nesting in fields close to this small mammal habitat had lower rates of predation. Adding in tall grass strips and patches within a farmland landscape could potentially increase the populations of small mammals, thereby distracting foxes and mustelids, and reducing predation pressure.  Avian predators of wader chicks might appreciate this intervention too!  This work is published as:

The influence of landscape features on nest predation rates of grassland-breeding waders by Rebecca A Laidlaw, Jennifer Smart, Mark A Smart & Jennifer A Gill in Ibis 157:4 Oct 2015

Over the last two years, the RSPB/UEA team has worked with landowners of commercial grasslands across East Anglia, who between them are responsible for a large percentage of remaining breeding wader populations. Building on the work on reserves, the aim was to understand whether habitat suitability and predation processes differ between reserve and wider countryside waders.  To accomplish this, they assessed the extent to which grassland management options within agri-environment schemes support small mammal populations, as well as measuring field wetness, Lapwing densities and nest predation rates.  They also assessed the importance of different nest predators for waders nesting in the wider countryside and within nature reserves.

A weasel leaves its mark: Becky Laidlaw

A weasel leaves its mark: Becky Laidlaw

Becky and her team found similar distributions of small mammals in the wider countryside as had already been found on nature reserves.  Within both, there were higher densities of small mammals within grassland habitats outside of fields, while presence within fields did not vary significantly among fields managed under different grassland agri-environment options.  Encouragingly, densities of Lapwing nesting in fields managed in accordance with the breeding wader option were significantly higher than in fields with no interventions. Lapwings nesting in areas with many other Lapwings and nests that were closer to patches of small mammal habitat were less likely to be predated, but the rate of Lapwing nest predation did not differ between the wider countryside and reserves.  It should be possible, therefore, to create Lapwing hot-spots outside of nature reserves, thereby expanding the reproductive potential of East Anglia.  Unsurprisingly, given the previous findings about the causes of nest-losses on nature reserves, wider-countryside sites where foxes were present experienced both higher overall nest predation and nocturnal nest predation.

Redshank also benefit for management designed to support Lapwings and probably appreciate the shared look-out duties Photo: Richard Chandler

Redshank also benefit for management designed to support Lapwings and probably appreciate the shared look-out duties Photo: Richard Chandler

The main findings of this study are that wader nest predation rates and spatial patterns of nest predation on lowland wet grasslands are remarkably similar inside and outside reserves. This should help to directly inform the design and development of lowland wet grassland landscapes, making them capable of attracting and supporting sustainable populations of breeding waders within the constraints of commercial grasslands.  Jen Smart is optimistic; “If we can provide wet fields that look attractive to Lapwings in spring and patches of tall vegetation that hold high numbers of small mammals it ought to be possible to improve nesting success and productivity”.  She and her colleagues are now looking at how a range of different agri-environment options might be used to create such landscapes.  The next phase of the project will be to try out the most promising options, in order to see the scale at which these patches of tall vegetation for small mammals need to be provided if they are to deliver the desired result – more breeding waders.

Update 

The are several other WaderTales blogs that may be of interest to people who like Lapwings:

For a full list of WaderTales blogs visit https://wadertales.wordpress.com/about/

 


 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