Migration of Scottish Greenshank

pic12 ringedIn the days of big data sets and complex analyses, it is pleasing that local, focused studies can still answer specific gaps in our understanding of migratory behaviour. Ron Summers and his colleagues have responded to a comment by Patrick Thompson, at the end of his contribution to The Migration Atlas, published by BTO in 2002: “… it is of major concern that we know so little about where Scottish birds [Greenshank] go once they leave the breeding grounds.” With a small number of geolocators and a few dozen plastic colour-rings, they are now able to answer this implied question, in a 2020 paper in Bird Study.

On the edge of range

Greenshank (or Common Greenshank) breed across the boreal zone of the Palearctic, from eastern Siberia in the east to Scotland in the west. The map below, produced by BirdLife International clearly shows that Scottish Greenshank lie at the southern and western extremes of this distribution. The species is even more widely distributed outside the breeding season; you can hear their three-note tew-tew-tew calls from New Zealand to the west of Ireland.

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Scotland holds a small population of Greenshank, estimated at 1440 pairs in 1995 (Hancock et al. 1997) but revised to be 1100+ in the latest population estimate in British Birds. This is a tiny part of a global population estimated as between 440,000 and 1.5 million individuals (Wetlands International). The lack of precision implicit in this large range is unsurprising; Greenshank tend to occur in small numbers in most of their wintering locations, not conveniently collecting in large flocks, such as Redshank or Knot.

pic4 breed mapThe northwest corner of mainland Scotland, together with the northern isles of the Outer Hebrides, are the main focus of the UK distribution, as is clear in the map showing relative abundance, taken from the BTO’s MapStore, based on Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC).

The Greenshank is far more widely spread across the British Isles in the winter. The three maps below, also based on data from Bird Atlas 2007-11 show a growth in the number of inland and east-coast sightings between 1981-84 (left) and 2007-11 (middle), with the highest densities in west coast sites in Ireland and Scotland.

pic2 winter maps

The Greenshank of Tongue

pic7 breed adultThe sound of a calling Greenshank takes me back to an Easter holiday that involved cycling into the wind (and odd snow flurry) along the A roads of the north coast of Scotland. These elegant waders are very much at home in this terrain of bogs, moorland and rocky outcrops. The study area for the project at the heart of this blog was near Tongue, two-thirds of the way from John o’ Groats, in the east, to Cape Wrath, in the west.

Between 2010 and 2015, twenty-four breeding Greenshank were trapped at the nest, by laying a mist-net over them. All were colour-ringed (most uniquely) and geolocators were attached to twenty of them. In most cases, feather samples were taken to determine gender. As many as possible of the geolocators were retrieved when the birds returned to breed, by again catching birds on their nests but one was recovered by a French hunter and another when a bird was recaptured in North Wales.

pic11Tongue

Stories from colour-rings

Prior to this study, the only ringing recoveries of Scottish-breeding birds refer to a chick ringed at Forsinard (Sutherland) on 6 June 1926 and shot in Ireland four months later, and a chick ringed in Perthshire in June 1974 and shot in northwest France that September. As both of these were autumn records, the young birds could still have been on migration when shot. The first definite winter location was established when an adult colour-ringed in Sutherland in 2010 was found to winter in Essex (eastern England).

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Ten of the colour-ringed birds from Tongue have been seen away from the breeding grounds: two in Scotland, five in Ireland and one each in Wales, northwest England, southeast England and southwest France. These movements represent migrations of between 530 km and 1560 km, which must seem unimpressive to a Greenshank that flies 10,000 km to reach southern Australia. Scottish colour-ringed birds have been seen on staging areas but once they arrive in their wintering areas in late June and July, they don’t move again until the following March or April.

In the case of one pair of Greenshank, both male and female were ringed and resighted. The male was in Wales and the female in France. If you have read Black-tailed Godwits: the importance of synchrony, this will come as no surprise!

Additional data from geolocators

pic10 scanColour-rings cannot really establish whether migration is non-stop or staged, just because sighting probability is low. By using geolocators, which collect data on the timing of dusk and dawn, it is possible to work out where individuals go between one year and the next – as long as you can re-catch individuals wearing geolocators! Seven geolocators were recovered (five by recapture of breeding birds, one shot in France and one recaptured at its Welsh wintering site – see image alongside). One geolocator did not work but there was sufficient information from the other geolocators to show that:

  • Geolocations for four birds indicated that they spent the winter in Ireland (but geolocators do not give precise information and one of these birds was actually seen (and subsequently caught) in North Wales)
  • One bird spent the winter in France (proved by being resighted and later shot there)
  • One tagged bird was recorded as being in Ireland in September, after which data collection ceased
  • Median departure date from northern Scotland was 16 July
  • Median arrival date in final wintering locations was 17 July
  • One Irish-wintering bird staged for two days in southwest Scotland
  • The French wintering bird appeared to spend a day in southern Ireland on its way south and to stop off in northern France on its way north.

Context and conclusions

pic6 chickAlthough the Summers et al Greenshank study only involves a small number of birds, it seems that Scottish birds do not migrate far, with none seen outwith Ireland, Britain or France.  Further, the data from the geolocators, which do not rely on birdwatchers spotting the birds, provided no evidence of birds going further south than France.

Although the migration distances were relatively short, there was some staging during southward and northward migrations.  For most birds, there was no staging and they could have accomplished the migration distance to Ireland or Wales (500-700 km) in about 10 hours, if flying at 60 km per hour (Alerstam et al. 2007).

The size of the wintering populations of Greenshank in Ireland, Great Britain and France are estimated as 1,265, 810 and 200, giving a total population of about 2,300 in these countries.  The breeding population in Scotland in 1995 was estimated as being between 1,100 and 1,790 pairs. Adding in chicks might mean that 4,000 birds are on the move each autumn. Although this value is higher than the numbers counted in Ireland, Britain and France in winter, the authors suggest that the two values are not so far apart as to discount the conclusion that the majority of birds from these wintering populations are derived from the Scottish-breeding population.

Winter visitors and passage migrants

pic1 BTO mapThe map alongside shows the movements of ringed Greenshank to and from Britain & Ireland, as extracted from the BTO’s online ringing report on 20 March 2020. There is evidence of the classic leap-frog migration, with individuals that breed further north spending the winter months further south. British breeding Greenshank may not move very far but many birds from Norway, Sweden and Russia spend time in Britain on their way to western African countries such as Ghana and Ivory Coast. Spring records in Italy suggest some birds might take a more easterly route on their way north.

Data from a UK-based colour-ring and tagging programme, coordinated by Pete Potts of Farlington Ringing Group, are being analysed. Initial findings suggest that a single estuary can host birds from a range of breeding locations. Some passage birds stay to complete moult but others just fatten and move on. We should soon know more about the relative importance of these British stop-over sites to western European Greenshanks.

pic8 bandwTo read the paper

The full story is available in Bird Study: 

Scottish-breeding Greenshanks Tringa nebularia do not migrate far. Ron Summers, Nick Christian, Brian Etheridge, Stuart Rae, Ian Cleasby and Snæbjörn Pálsson. Bird Study. March 2020.

The study was a Highland Ringing Group project, supported by the Scottish Ornithologists’ Club Endowment Fund.

More about migration

If you found this blog interesting, here’s a selection from the WaderTales catalogue that may also appeal. The first two articles reveal the results of a local study of Green Sandpipers that spend the winter in Hertfordshire.

In the next two blogs, you can read how migration patterns vary in Oystercatchers, depending upon how far north birds breed, the locality in which they nest and the obstacles that lie in the way if they undertake migratory journeys.

And this blog is all about ‘happenstance’, the seemingly random processes that presumably determine why Sanderling from the same small part of Greenland may fly as far as South Africa or just to Scotland:

pic9 flying


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

 

Where to nest?

pic whimbrelThere is nothing more obvious than an Oystercatcher sitting on his or her nest, but a brooding Snipe can be invisible until almost trodden upon. Which strategy works better: nesting in plain view but laying cryptically camouflaged eggs or hiding yourself and your nest in a clump of grass? Which species is most likely to hatch a successful brood of chicks and in what circumstances? In a 2020 paper in IBIS, Becky Laidlaw and colleagues analysed nest site characteristics and nest locations of 469 wader nests in Iceland in order to provide some answers

The perils of ground-nesting

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Hatching Whimbrel eggs, with the tell-tale shell fragments that signal a nesting attempt has been successful

Almost all waders are ground-nesters, which makes them highly vulnerable to a wide range of nest predators. To reduce the risks of predation, different strategies have evolved. In some species, nests are placed out in the open, and the camouflage is provided only by mottled egg colouration that resembles the background. In other species, nests are secreted in vegetation, meaning eggs and incubating adults are concealed from predators.

In both groups of species, the risk of nests being predated might vary, depending on the surrounding habitat. For open-nesting species, for example, clutches that are laid in large patches of similar habitat may be harder for predators to locate. The same could apply to closed-nest species that hide their nests; Snipe nests may be tricky to find in extensive areas of long grass but perhaps more at risk if there are only a few suitable clumps of long grass that predators need to check out.

pic hidden Redshank

Iceland: a wader factory

tableAs discussed in previous WaderTales blogs, particularly Do Iceland’s farmers care about wader conservation? Iceland is hugely important as a European ‘wader factory’. As farmland elsewhere has become less suitable for species such as Redshank and Snipe, the global importance of the country has increased (see table alongside for most recent figures from an AEWA report)  With this in mind, it is important to understand the factors that underpin the population dynamics of Iceland’s breeding waders.

Working in South Iceland, Becky Laidlaw and her co-authors tried to find as many nests as possible during the summers of 2015 and 2016. This area is largely a mosaic of open habitats, although there are more patches of forestry than there were twenty years ago. Most of the Southern Lowlands area is farmed, on a gradient between intensive and semi-natural, and this is reflected in the distribution of breeding waders (see Farming for waders in Iceland).

pic rope

Dragging a light rope across the vegetation to flush nesting birds

For this project, nests were located by surveys from vehicles and on foot, through observation of incubating adults, systematic searching, incidental flushing of incubating adults and rope-dragging (dragging a 25 m rope, held between two fieldworkers, lightly across vegetation) to flush incubating adults.

The analysis in the resulting paper in IBIS focuses on 469 nests of three open-nesting species (Oystercatcher, Golden Plover and Whimbrel) and three species that hide their nests in tall vegetation (Redshank, Snipe and Black-tailed Godwit). The team recorded the habitat and vegetation structure around each nest (at the nest, within a 5 m x 5 m square and in a wider 50 m x 50 m square) and worked out which nests hatched successfully and which were predated. The date and time of predation were determined, where possible, with nest-cameras providing extra information for some nests. Cameras captured nest-predation events involving Arctic foxes, Arctic Skuas, Ravens and sheep.

Interestingly, 2015 and 2016 were very different wader breeding seasons. The graphic below shows the mean temperatures for the months from April through to July (encompassing the wader breeding season at this latitude) were much cooler in 2015 than in 2016, representing average monthly difference of between 1.5°C and 2.5°C. At high latitudes these figures translate into very different rates of vegetation growth.

pic pretty graph

First, find your nest

When nests were first located, their positions were marked and referenced using GPS. Eggs were floated in water to provide an estimate of laying date and thereby predict hatching date. As the chick develops within an egg, the density of the egg falls. A newly laid egg will lie on the bottom of the flotation vessel. Over the next few days the ‘blunt end’ rises until the egg is still touching the bottom but vertical. Eggs in the late-development stage float ‘point-end-down’, with the latest eggs floating at an angle to the vertical (method described by Liebezeit et al.).

pic skua-ed goldie eggs

This Golden Plover nest was probably predated by an Arctic Skua

Nests were considered successful if one or more eggs hatched, and predated nests were defined as those that were empty in advance of the predicted hatch date or those without any eggshell fragments in the nest (a sign of successful hatching). To determine the time and date of nest failures, iButton dataloggers were placed in a randomly selected subsample of nests. These loggers recorded a temperature trace every ten minutes. A sharp and permanent decline in nest temperature below incubation temperature indicates nest predation. In both study years, motion-triggered cameras were deployed on a sample of open-nesting species to determine the predator species active on these nests.

When each nest was first located, the percentage of eggs visible from directly above the nest was estimated and the habitat surrounding each nest was assessed in the field at three spatial scales: the nest cup, the 5 m x 5 m and the 50 m x 50 m area surrounding each nest. Details are in the paper.

Which nests survive through to hatching?

Over the breeding seasons of 2015 and 2016, the outcomes of 469 wader nests were assessed. 259 hatched successfully (55%), 192 were predated (41%), 13 were abandoned, 7 were trampled and 2 were mown. A nest-loss rate of 40% is fairly typical for ground-nesting waders, when compared to studies in different countries and habitats.

pic fox attack

Daily nest predation rates did not vary significantly in relation to the habitat heterogeneity or the extent to which the dominant habitat covered the area surrounding the nest, at either 5 m x 5 m or 50 m x 50 m scales. Most clutches were laid in habitats that were the same or similar to the surrounding areas. Where there were differences, the dissimilarity between the habitat at the nest cup and in the surrounding area did not influence daily nest predation rates for open- or closed-nest species. Although nest predation is high, at about 40%, incidence of predation events appears to be unpredictable – or even random.

pic snipe nest

In cold spring conditions, Icelandic Snipe are not able to hide their nests

Daily nest predation rates were significantly higher for closed nests (Redshank, Snipe and Black-tailed Godwit nests) in which a greater percentage of the clutch was visible. This suggests that the onset and rate of vegetation growth could potentially constrain the availability of suitable nesting locations for these species, and hence influence nest success, particularly among early season nests. This has been studied in Icelandic Black-tailed Godwits by José Alves and colleagues and is described in From local warming to range expansion.

For closed-nest species, the visibility of nests was significantly greater during the early part of the 2015 breeding season, when compared to 2016, due to slower grass growth in cooler conditions.  The higher predation rate of more visible nests of closed-nesting species was apparent even though nests were predated up to three weeks after egg visibility was measured. These findings suggest that early nesting attempts by concealed-nest species are unlikely to be successful in years when vegetation growth is delayed or slow. There can be major benefits of hatching early, with recruitment into breeding populations typically being lower for later-hatched chicks, so vegetation growth rates are likely to be really important to species that conceal their nests (Redshank, Snipe & Black-tailed Godwit in this study). However, given the ongoing trend for warmer springs at subarctic latitudes, the conditions in which early nests can only be poorly concealed are likely to be reducing in frequency.

In summary

pic goldie nest in habitat

Golden Plover nest set within a homogeneous habitat matrix

Perhaps surprisingly, nest predation rates were similar for open-nest and concealed-nest species and did not vary with vegetation structure in the surrounding landscape. However, nest-concealing species were about 10% more likely to have nests predated when the nests were poorly concealed, and the frequency of poorly concealed nests was higher at the start of the breeding season in colder conditions.

The paper at the heart of this blog is:

Vegetation structure influences predation rates of early nests in subarctic breeding waders. Rebecca A. Laidlaw, Tómas G. Gunnarsson, Verónica Méndez, Camilo Carneiro, Böðvar Þórisson, Adam Wentworth, Jennifer A. Gill and José A. Alves. IBIS. doi:10.1111/ibi.12827

pic sheep


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

 

 

Black-tailed Godwits are on their way home

bg topAs I write this, at the start of March 2020, spring is on its way – and so are limosa Black-tailed Godwits. Many have flown north from wetlands and rice-fields in West Africa and are now fattening and moulting in a small number of sites in Portugal, France and Spain. The vast majority are heading for the Netherlands but a few will ‘bear left’ and end up in East Anglia.

The biggest spring flocks of limosa Black-tailed Godwits are found on the Tagus (or Tejo) Estuary, in Portugal, a site that is under threat from a planned airport development. Swirling flocks of up to 80,000 birds create a wildlife spectacle that attracts an increasing number of tourists. Among these ranks of telescope-wielding birdwatchers is a small band of dedicated colour-ring readers from the Netherlands working on a University of Groningen / Global Flyway Network project. They are looking for marked Black-tailed Godwits (Grutto in Dutch) that are part of their conservation science project; some of these Grutto are old friends, others will have been ringed as chicks and are now heading north for the first time.

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This year, the Dutch team working in Portugal in mid-February spotted ten Project Godwit birds – Black-tailed Godwits that belong to the tiny and highly threatened population that breed in the Ouse and Nene Washes. An increasing number of these sightings of English birds are of ‘head-started’ godwits; birds that started life as eggs in nests on the RSPB’s Nene Washes reserve and were then hatched in incubators and reared in captivity at the Wildfowl & Wetland Trust’s Welney reserve. You can read more about head-starting here.

Before telling some fascinating individual stories, here’s a quick reminder that conservation operations in The Netherlands, the UK and elsewhere might be jeopardised by a plan to build a second airport for Lisbon, within the Tagus Estuary – one of the top wetlands in Europe and a critical stopover site for limosa godwits.

Birds v Planes

bg petitionMillions of euros – and a smaller number of pounds – are spent each year in support of the dwindling populations of limosa Black-tailed Godwits that breed in the Netherlands, here in the UK and in other countries within Europe. Much of the money is helping ‘meadow birds’ in general but there are specific interventions to protect godwit nests and chicks during farming operations in the Netherlands and to boost chick production in England. These huge (and often expensive) conservation efforts are potentially being threatened by a plan to build the so-called Montijo Airport in the heart of the Tagus Estuary. This is where up to 80,000 Black-tailed Godwits gather in spring and several thousand spend the winter. You can read more about the planned airport and the importance of the area to migratory waders and other waterbirds in Tagus estuary – for birds or planes?

You can support the Dutch initiative to stop the new airport by signing the petition being organised by Vogelbescherming, the BirdLife partner in the Netherlands. Link here.

Last chance for England’s breeding Black-tailed Godwits

When Project Godwit started in 2017, there were only 38 pairs of Black-tailed Godwit breeding in East Anglia, mostly on the Nene Washes, with a small number on the Ouse Washes. Despite huge efforts by conservation organisations, and the RSPB in particular, productivity was consistently very low. Predation and flooding were the main challenges; there was a real prospect of ageing birds failing to raise enough youngsters to maintain the viability of the population. While work continued to create alternative flood-free breeding areas at the Ouse Washes and to tackle predation issues, these godwits needed a boost. That’s where head-starting comes in; by removing first clutches, incubating the eggs, raising the chicks and releasing them back onto the Nene and Ouse Washes, once fledged, it proved possible to greatly increase the number of young birds that headed south for the winter.

Sep2019

At the start, there was no guarantee that head-starting would work. The first WaderTales blog about Project Godwit was a plea for birdwatchers to look out for colour-ringed, head-started chicks, the second asked whether the released chicks would be able to find their way back to East Anglia and the third celebrated early successes.

  1. Special Black-tailed Godwits
  2. Site-fidelity in Black-tailed Godwits
  3. Head-starting success

The success of these special head-started Black-tailed Godwits has been enjoyed by millions who watch the BBC’s Springwatch series and thousands of visitors to the WWT centre at Welney. In addition, individual godwits have played starring roles in newspaper and magazine articles and on local television news programmes.

bg map

Migration

bg SenegalOne of the big take-home messages from Project Godwit is that head-started chicks, released back on the Ouse and Nene Washes, soon mix with wild-reared birds and adults.  Information collected so far suggests that head-started birds follow similar migration patterns to the wild godwits.  Most limosa Black-tailed Godwits travel south to countries in West Africa, especially Senegal, and then fly north after Christmas, to Portugal and Spain.  Some may make another stop in France, before reaching their territories. An increasing proportion of the main Dutch population is now wintering in Europe (Should Black-tailed Godwits cross the Sahara?). Dutch and Iberian researchers are using satellite tracking to monitor day-to-day movements (King of the Meadows)

Birds on the Tagus in 2020

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Black-tailed Godwits feeding in a Tagus rice-field

Some limosa Black-tailed Godwits spend the winter on the Tagus but big flocks do not start to build until the start of the new year, as birds return from Africa. The ten colour-ringed Project Godwit individuals that were seen by the Dutch team between 2nd and 10th of February 2020 were a mixture of old friends and birds that had not been seen on the rice fields before. Flocks of 30,000 or more Black-tailed Godwits can descend upon a single rice-field, post-harvest, to feed on spilt grain and invertebrates. It is not easy to spot colour-ringed birds in the melee of legs, as birds wade through the water, and it is very likely that there were many more Washes birds that were not spotted. The ten Project Godwit birds were seen alongside hundreds being studied by Dutch conservation scientists. So, which individual godwits were seen?

Class of 2017

Two head-started chicks from the first year of the project were seen in February 2020. One of them was YG-GL(E) or Remi (click on her name to read her story), who starred in the WaderTales blog Site-fidelity in Black-tailed Godwits. We know that she is one of the majority of Black-tailed Godwits that fly to West Africa because she was also spotted in Senegal in November 2019. A total of 24 head-started birds were released in the summer of 2017 and six of them have now been seen on the Tagus.

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Class of 2018

bg HurricaneIn the summer of 2018, 38 head-started chicks were released and two of them were seen this February in the Tagus rice-fields. One of these was WG-WL(E) or Hurricane, a bird that spent his first summer near Valencia in Spain before departing in mid-June. Some Black-tailed Godwits fly north in their first spring but many do not. After months of Spanish sunshine, Hurricane may well have flown south with an early flock of post-breeding adults, moving through to West Africa in the late summer,  and that the Dutch team spotted him on his way back to the Washes. Two other head-started birds from the second year of the project have been seen on the Tagus, making a total of four.

Class of 2019

The 48 head-started birds from 2019 are still only a few months old. Some might be on their way back to the Washes but there were no sightings in early February. It has been suggested that birds that do migrate north to breed in their first year might be on a slightly later schedule, so perhaps later teams of Dutch observers might report one or more of these birds.

Wild chicks 2017-2019

bg ad chicksThe Project Godwit team try to ring as many as possible of the wild-reared chicks on the Nene Washes, so that they can compare their behaviour patterns to those of the captive-reared group. Two of the wild-reared birds have been seen on the Tagus; a chick from 2018 was reported in both 2019 and 2020, and a chick from 2019 was seen in the autumn of 2019.

Earlier chicks

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Two members of the Dutch team of colour-ring readers: Rienk Jelle Hibma & Teade de Boer

The RSPB has been studying Black-tailed Godwits for over twenty years. One of the very early chicks was spotted in the rice-fields this February. LG-RL(E) was ringed 21 years ago and she had previously been reported in the Tagus estuary in the springs of 2017, 2018 and 2019, and in the autumn of 2018. Black-tailed Godwits are known to live for up to 25 years.

Ringed as adults

RSPB researchers also ring adults by catching them on their nests. Four birds ringed in this way were seen on the Portuguese rice-fields in February 2020. Adding in four head-started chicks, and two chicks that was raised in the wild, this makes a total of ten birds from the Ouse and Nene Washes that are known to have visited the Tagus Estuary during this spring.

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There are two colour-ringed birds in this photograph

One that won’t be seen again

RY-OL(E) was ringed in 2002 and spotted in the Tagus in February 2018. She has been a key contributor to Project Godwit over the last few years, fledging two chicks in the wild in 2018 and three in 2019. Additionally, she provided four extra young godwits via the head-starting process in 2018. Her metal-ringed leg was recently found in a Peregrine nest in Brighton. Presumably she became a meal for a young Peregrine in the late summer of 2019.

Conservation importance of the Tagus Estuary

In February, the Tagus is thought to hold half of what is left of the Dutch population of Black-tailed Godwits, when up to 80,000 birds move around the estuary in huge flocks. Colour-ring reports and sighting probabilities suggest that around half of the Project Godwit birds, heading for the Ouse and Nene Washes, may also rely on the mud-flats and surrounding rice-fields in the early spring.

bg Hotting

Project Godwit has already given a terrific boost to the Black-tailed Godwits breeding in England, with the number of pairs up from 38 in 2017 to 45 in 2019, and it seems ridiculous that much of the good work could be put at risk if Montijo Airport is built. It is sad that a five-year project, that has involved over 20 dedicated RSPB and WWT staff , together with local volunteers and observers in the UK, Europe and Africa, might be in jeopardy.

Project Godwit has received major funding from the EU LIFE Nature Programme, HSBC 150th Anniversary Fund, Natural England, the Heritage Lottery Fund (through the Back from the Brink Programme) and Leica UK. The Dutch team of colour-ring readers in February 2020 was: Jan Vegelin, Kees de Jager, Egbert van der Velde, Rienk Jelle Hibma, Teade de Boer, Bob Loos & Jacob de Vries.  Their work is directed by Jos Hooijmeijer and funded by the University of Groningen and the Global Flyway Network.

bf afonso pump


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

Curlews and foxes in East Anglia

blog chicksWith Curlew populations in free-fall across much of the British Isles, researchers are trying to understand the reasons for poor breeding performance. At the same time, several groups are trialling emergency interventions, such as predator control and predator exclusion, to try to boost the number of fledged chicks. Sharing knowledge is crucial, so it’s great that a 2020 paper by Natalia Zielonka and colleagues in Bird Study adds to our understanding of nest-site selection and the reasons for nesting failures.

Breckland Curlew

When we think of Britain’s breeding Curlew, the traditional image that comes to mind is moorland, where displaying birds deliver their haunting, bubbling call across upland heather moor and sheep pasture. In lowland East Anglia, in the east of England, things are very different. Some Curlew nest on Breckland heaths, which are structurally similar to moorland, but you can also find nests in sugar-beet field, in military training areas and around airfields.

The Eurasian Curlew is now categorised as Near Threatened by IUCN & BirdLife International, due to populations declines (see Is the Curlew really near-threatened?). Figures from the Breeding Bird Survey for the period 1995-2017 show that the situation in England (30% decline) is less bad than Scotland (down 61%) or Wales (down 68%). The species is now too thinly spread to be monitored in Northern Ireland but we know that the breeding population in the Republic of Ireland dropped from 3,300 pairs to just 138 pairs in 30 years (more in Ireland’s Curlew Crisis). In this context, the hot-spot in Breckland (see left-hand map from Bird Atlas 2007-11) is significant, as is the fact that there are four 10-km squares in East Anglia where an increase in density was noted between 1988-91 and 2008-11 (right).

blog maps

Problems for Curlew

The main driver of UK Curlew decline is low breeding productivity, attributable to predation and reduced quality of breeding habitats (see review by Franks et al., summarised in Curlews can’t wait for a treatment plan). Research has informed habitat provision and demonstrated that legal predator control (of foxes, crows, stoats and weasels) can increase Curlew breeding success and abundance – but not in all cases.

blog flyingMuch of the research underpinning the above review was conducted in upland areas. What is happening in the flatlands of East Anglia and might any differences explain the apparent resilience – or even growth – of this population? Most lowland Curlew breed on dry grasslands and heathland, where physical ground-disturbance is increasingly advocated as a land management technique for other rare, scarce and threatened species, such as Stone-Curlew and Woodlark. How do these interventions affect breeding Curlew in the same areas?

Study site

Natalia and her colleagues studied Curlew in two extensive grass-heath sites that differed in predator density and management. Across both sites, vegetation structure had been modified, using ground-disturbance plots, as part of a wider multi-taxa experiment, aimed at increasing biodiversity and supporting key species such as Woodlark (paper in Ibis) and Stone Curlew (paper in Biol. Conserv.).  This disturbance involved creating  2 to 4 hectare plots of deep- or shallow-cultivated ground within the wider grassland/heathland environment.

Before the experiment began, and based on previous research elsewhere, it was assumed that Curlew would avoid physically-disturbed areas, given that Curlew have been shown to prefer to nest in rougher habitats with longer grass swards.  Wherever the Curlews decided to nest, it was predicted that nest survival would be higher on the site with lower predator density, that most clutches would be taken at night and that success would decrease through the season.

blog STANTA

The study was carried out in 2017 and 2018 across the Stanford Military Training Area (STANTA) and Brettenham Heath. Both sites contain extensive areas of dry grassland and grass-heath, surrounded by arable farmland and woodland. Generalist predator control on STANTA was largely carried out around Pheasant release pens, with little or none in most of the surrounding, open arable farmland and woodland. In contrast, Brettenham Heath was subject to continuous predator control across the whole site and in surrounding arable farmland (but not woodland). Brettenham Heath is also enclosed by a two-metre high deer fence with a single electric strand set 50 cm above the ground. There is more about the two sites in the paper (link below).

blog Brettenham

Across both sites, 64 experimental ground-disturbance plots were established in early 2015 and subsequently disturbed annually, using a variety of management techniques. Areas on STANTA that might have contained unexploded ordinance could not be disturbed – and were trickier to survey! In both years, nests were located between mid-April and late June, by visiting any area where Curlew had been seen and looking for adults sitting on, or walking back to, a nest.

Evidence of nest success

blog chickTo determine the date and timing of nest failure, temperature sensors were placed under the eggs. Nests were remotely checked every three-to-seven days, to confirm adults were still incubating, and the scrape was visited once a week to record any predation events (e.g. partial clutch predation). From three days before the predicted hatch date, nests were remotely monitored daily to accurately determine their fate. After hatching, the nest site was visited every three-to-five days, to observe adults and chicks from a vehicle, continuing until the chicks fledged or the breeding attempt had failed.

Three types of evidence can help to reveal the outcome of a nesting attempt:

  • Small chicks or alarming adults are seen in the vicinity of an empty nest.
  • Small shell fragments are found in the nest cup, indicating that chicks have hatched.
  • The temperature sensor reveals that adults kept the eggs warm for the whole incubation period.

A sudden drop in nest temperature can reveal the timing of predation and hint at the culprit. Other studies have shown that nocturnal visits are usually by foxes or badgers, or occasionally hedgehogs. In 2018, infra-red cameras, triggered by movement, were used on ten nests.

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Where to nest?

Unexpectedly, given that breeding Curlew in the uplands are usually associated with areas with longer grass, Breckland pairs were five- to six-times more likely to select disturbed plots than undisturbed grassland. Nearly half of nests were located on disturbed grassland across both years, which only occupied about 8% of the grassland area. Curlew are long-lived and site-faithful, so disturbed plots may have been created within already-established breeding territories. Whilst physical-disturbance interventions are unlikely to bring birds in from the wider landscape, this study shows that nest placement was more likely to occur on disturbed grassland within a pair’s home range. This suggests that local-scale management can influence nest placement within established breeding sites.

Disturbed grassland is characteristically bare and short compared to uncultivated grassland. Curlew may have placed nests in this habitat because it allows greater vigilance and/or because there is a greater abundance of some important prey for chicks than the surrounding grassland (information in paper by Hawkes et al.). Most nests were on shallow-cultivated plots (created with a rotary rotovator), with few on the barer deep-cultivated plots (created with an agricultural plough). There was taller vegetation and more ground cover in the shallow-cultivated plots.

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Nest survival rates                                                                                                                       

Over the course of the two summers, 44 Curlew nests were monitored, of which 32 failed. 29 nests were predated, one was trampled by livestock, one was mown and one pair deserted (and then renested). Mean overall nest survival probability from start of incubation to hatching was 0.70 ± 0.18 SE at Brettenham Heath (where there was intensive predator control and fencing) and 0.16 ± 0.06 at STANTA (where predator control was patchy and the site was open). Overall breeding productivity was 0.16 ± 0.01 SE fledged chicks per nesting attempt. As predicted, daily nest survival rate decreased through the course of the nesting season.

The figure for STANTA represents low nesting survival, especially when compared to other lowland sites in England, and re-nesting following failure appeared infrequent. Productivity here is likely to be substantially below that required to maintain a stable population. Importantly, nest survival across the two sites was not influenced by ground-disturbance, which suggests that this management intervention did not increase nest exposure to predators.

Identifying the predators

D4_sheep_predation_20May

Sheep versus Curlew

Of the ten 2018 nests with nest cameras:

  • Three nests survived through to hatching.
  • Four were predated by fox (one during the day and three at night).
  • One nest was predated by an unknown predator (following camera malfunction).
  • One nest was predated by a sheep (two out of four eggs remained but incubation was not resumed and the other eggs were later taken by a crow).
  • A single-egg, late-season re-nesting attempt was abandoned three days after camera deployment (egg was later taken by a crow)

There was no effect of nest cameras on daily nest survival rate.

G1_Fox_predation_20May

Fox versus Curlew

Parent Curlews removed some of the temperature loggers but there were sufficient data to identify the timing of predation events for 23 nests. Of these, 17 events were during the night (13 nocturnal, four crepuscular) and six during the day. This nocturnal timing of nest predation was consistent with mammalian rather than avian predation, with camera traps and other evidence suggesting that foxes were the main perpetrators.

As expected, from the levels of predator control, nest survival was lower at STANTA than Brettenham Heath. The latter site was both fenced and subject to lethal fox control, delivering a breeding productivity well above that considered necessary for a sustainable population of Curlew. It is possible that a few fenced sites and others with high levels of predator control might be disproportionately responsible for the fact that Curlew appear to be doing better in the Brecks than in other areas.

Conservation implications

blog bare nestThe key finding of this project is that physical ground-disturbance, which is advocated as a conservation measure within lowland dry grassland and grass-heath for many rare, scarce and threatened species, also provides suitable Curlew nesting habitat, with no reduction in nest survival. Implementing ground-disturbance, particularly through shallow-cultivating, in areas with few or no mammalian nest predators, could provide a useful management tool for attracting breeding Curlew to safer areas.

An intervention to help Stone Curlew and Woodlarks was never designed to assist Curlew. Indeed, there was a prediction that Curlew would actively avoid areas that had been rotovated, in order to create bare patches in which the target species could nest and feed. In a rare case of serendipity, experimental research by Rob Hawkes, Paul Dolman and others has delivered a way of encouraging Curlew to nest in relatively small plots (2-4 hectares) around which it may be possible to run an electric fence. One of the big questions “How can we protect Curlew nests when they have such big territories?” might have become easier to answer. If ‘Curlew plots’ can be created within known territories, or even areas that seem good for Curlew, then they can potentially become the focus for protection.

Having spotted that Curlew seemed to be attracted to disturbed areas it is great that Natalia Zielonka was able to study this population, in order better to understand constraints that seem to be restricting productivity. Her research was undertaken as part of her MSc in Applied Ecology and Conservation at the University of East Anglia,

Further reading

blog RARThe paper at the heart of this blog is:

Placement, survival and predator identity of Eurasian Curlew Numenius arquata nests on lowland grass-heath. Natalia B. Zielonka, Robert W. Hawkes, Helen Jones, Robert J. Burnside & Paul M. Dolman.

Bird Study. DOI 10.1080/00063657.2020.1725421


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

Which Icelandic Oystercatchers cross the Atlantic?

blog ringed birdMost Icelandic Oystercatchers leave Iceland in the autumn, crossing the Atlantic and arriving in Ireland, the UK and mainland Europe. Despite much shorter day-length and colder conditions, 30% spend the winter in Iceland, as discussed in this blog (Mission Impossible).

A 2020 paper from Verónica Méndez and colleagues asks whether birds that stay in Iceland or cross the Atlantic differ in sex, body-size or breeding location (within Iceland) and whether birds behave differently in different years. Interestingly, they were also able to test whether there is assortative mating – do Oystercatchers that stay in Iceland pair with other stay-at-home birds?

Iceland’s Oystercatchers

Iceland lies at the northern edge of the breeding range of Eurasian Oystercatchers. The country supports an unusually high proportion of wintering Oystercatchers, given its latitude and winter temperatures (Þórisson et al. 2018), and this may be influenced by the trans-oceanic flight of at least 700 km that migratory individuals must undertake to reach the European wintering sites. Individuals that migrate or stay within Iceland could differ in body size, for example if size influences the capacity to survive adverse winter conditions. Females tend to be slightly larger, and thus any sex differences in migratory behaviour could potentially reflect differences in body size.

It would be easy to imagine a scenario in which Oystercatcher pairs try to breed as early as possible, as this could increase the number of potential nesting attempts, as discussed in Time to nest again, based on Morrison et al. 2019. Does this mean that stay-at-home birds pair off at the start of the season, before migrants arrive? Given that most birds will choose the same mate in successive years, what happens in mixed pairs if a resident is waiting around for a delayed migrant? Is divorce likely to occur, as discussed in the importance of synchrony for Black-tailed Godwits, and could this mean that mixed pairs are rare?

Colour-marks and isotopes

blog map of sightingsA huge amount of the evidence that was used to answer the questions posed by Verónica and her colleagues was provided by volunteer birdwatchers, who reported colour-ringed Oystercatchers in their wintering areas, in the period through to April 2018. There’s an impressive set of dots on the map alongside, from the north of Scotland through to Spain, and the number of sightings continues to rise. It’s perhaps unsurprising, given the direction of travel from Iceland, that there is a strong westerly bias to the distribution across the British Isles.

The sample size from colour-ring observations was not big enough to answer all of the questions posed above, especially relating to whether pairs mate assortatively. To provide one data-point, it’s necessary to know the winter locations of both members of the pair. Might feather isotope ratios provide some help?

Oystercatchers that winter in Iceland use a restricted number of coastal sites (as inland sites are frozen during winter) and forage on marine prey. Elsewhere in Europe, a much wider range of marine and freshwater resources is available, with birds readily moving between the shoreline and fields, golf-courses, football pitches and road-side verges. Previous studies have shown that terrestrial diets produce different carbon and nitrogen isotope ratios, based on salinity and trophic level of prey items.  Are differences in habitat use and diet of Oystercatchers reflected in carbon (δ13C) and nitrogen (δ15N) isotope ratios of feathers grown during late winter?

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Oystercatchers moult their chest feathers in late winter

The research team hoped that isotopic signatures from resighted colour-marked migrants and residents would be sufficiently different to be able to predict the probable wintering areas (Europe or Iceland) of marked birds not seen away from their breeding sites. If so, this would greatly increase the sample size, by enabling the combination of data from observations of colour-marked individuals with information on birds that could be assigned as Icelandic or European winterers using the isotopic composition of their feathers. They predicted that it would then be possible to:

  • Identify migratory strategies of individual Oystercatchers and explore whether the likelihood of migrating or staying in Iceland is related to gender, body size or breeding location.
  • Assess how consistent these individual strategies are between years.
  • Quantify spatial variation in the distribution of migrants and residents across the Icelandic breeding range.
  • Determine whether Oystercatchers mate assortatively in relation to migratory behaviour.

The work covered in this paper was conducted between 2013 and 2017. Full details of the study areas and methods are available in the paper – link below.

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Early nesting is not always a good idea – still incubating after sudden snow-fall

Migrant or resident?

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An Icelandic Oysterctaher spending the winter in Co. Sligo in Ireland

Of the 537 colour-ringed adults in the study, 58 were seen away from Iceland and 55 were shown to be resident in Iceland. Oystercatchers undertake a partial moult at the end of the winter period, when they grow new feathers on the neck and chest. The isotopic signature of a tiny piece of one of these feathers, taken from each adult at the time of ringing or recapture, was determined. The values of δ13C, which relates to habitat salinity, and δ15N, which relates to trophic level of diet, varied between residents and migrants but there was an overlap (details in paper).  There was enough of a difference, however, for it to be possible to allocate two-thirds of ringed birds that had not been seen in the winter period to the resident and migratory categories, with sufficient certainty, thereby increasing the sample size for other tests.

Consistency of migratory tendency

The 18 individuals that were observed in more than one winter were all consistent in migratory behaviour (10 residents and 8 migrants) and each was seen in the same specific location (Iceland or western Europe) in both winters. Where feather samples were taken in more than one year, there was no evidence of any bird changing its habitat or diet.

Factors influencing individual migratory programmes

Females and males were equally likely to migrate and there was no evidence that bigger (or smaller) birds were more likely to leave Iceland. Most Oystercatchers that winter in Iceland are in flocks in the west of the country, where the coast is warmed by the Gulf Stream. Unsurprisingly, westerly breeders were more likely to be resident than those in the south or northeast of Iceland (see figure below).

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Assortative mating

Vero and her colleagues were able to assign the migratory strategy to both members of the pair for 162 pairs (either by resightings or using predictions from isotopic signatures). Among these, 75 pairs (46%) were both migrants, 32 pairs (20%) were both residents and 55 pairs (34%) were mixed. The frequency of full-migrant, full-resident or mixed pairs varied significantly among regions, which was to be expected, given the differences in the likelihood of migrating from different parts of Iceland. There was no evidence of assortative mating; the likelihood of a particular individual pairing up with a migrant was as expected from the proportion of migrants in the area; it was not influenced by whether the particular individual was itself a migrant (see figure above).

To migrate or remain in Iceland

The consistency of adult migratory behaviour suggests that migratory strategy is determined in early life, and the regional variation in the frequency of migrants and residents may thus reflect variation in the conditions encountered by individuals during this life stage. As noted above, the frequency of residency is greatest amongst Oystercatchers breeding in the west of Iceland, which are the areas closest to the main wintering locations. Juveniles from the northwest and west are more likely to encounter these flocks of adult and sub-adult birds when moving south, than juveniles from the south, north-east and east, which are more likely to encounter migrating adults.

blog gen chThe regional variation in migratory strategy could arise through the influence of social cues, with juveniles adopting the behaviour of Oystercatchers they encounter and then recruiting back into their natal locations (more about this in Generational Change, focusing on Black-tailed Godwits). Birdwatchers across Europe will hopefully help to test this theory, by tracking colour-ringed juveniles during the early years of life. This is all part of a quest to identify the conditions that influence migratory behaviour and to understand the consequences, in terms of survival rates and productivity, of adopting different migratory traits.

Paper

Please click on the title below to access the paper:

Individual variation in migratory behavior in a sub-arctic partial migrant shorebird by Méndez V., Alves J.A., Þórisson, B., Marca, A., Gunnarsson, T.G., Gill, J.A.  Published in Behavioral Ecology (2020).  doi.org/10.1093/beheco/araa010 

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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

 

Nine red-listed UK waders

blog rpIf you ask British birdwatchers to name the nine wader species that are causing the most conservation concern in the UK, they would probably not include the Ringed Plover. Curlew may well be top of the list, even though we still have 58,500 breeding pairs in the UK*, but would people remember to include Ruff? This blog is written to coincide with the publication of Red67, an amazing collaboration of artists and essayists that highlights and celebrates the 67 species on the current UK red list, nine of which are waders.

*Avian Population Estimates Panel report (APEP4) published in British Birds

What’s a Red List?

The UK Red List is made up of a strange mixture of common and rare species. Nobody will be surprised to see fast-disappearing Cuckoo, Turtle Dove and Willow Tit, but why are 5.3 million pairs of House Sparrow in the same company? The list is very important because it helps to set the agenda for conservation action, the way that money for research is distributed and focuses attention during planning decisions. The main criteria for inclusion are population size – hence the inclusion of species that are just hanging on in the UK, such as Golden Oriole – and the speed of decline of common species. Data collected by volunteers, working under the auspices of the British Trust for Ornithology, measured a population decline for House Sparrow of 70% between 1977 and 2017, which is worrying enough to earn this third most numerous breeding species in the UK a place in Red67.

blog bookIn his foreword to Red67, Mark Eaton, Principal Conservation Scientist for RSPB, explains how listing works. The Birds of Conservation Concern (BOCC) system, through which the Red List and Amber List are determined, uses a strict set of quantitative criteria to examine the status of all of the UK’s ‘regularly’ occurring species (scarce migrants and vagrants aren’t considered), and uses a simple traffic light system to classify them. There are ‘Red’ criteria with thresholds for rates of decline in numbers and range, historical decline and international threat (if a species is considered globally threatened it is automatically Red-listed in the UK), together with a range of other considerations such as rarity, international importance of UK populations, and how localised a species is. If a species meets any of the Red List criteria it goes onto the Red List.

The Red67 book – words meet art

Red67 is the brainchild of Kit Jewitt, a.k.a. @YOLOBirder on Twitter. It’s a book featuring the 67 Red-listed birds, each illustrated by a different artist alongside a personal story from a diverse collection of writers. Proceeds will support Red-listed species conservation projects run by BTO and RSPB. Kit describes Red67 as 67 love letters to our most vulnerable species, each beautifully illustrated by some of the best wildlife artists around, showcasing a range of styles as varied as the birds in these pages. My hope is that the book will bring the Red List to a wider audience whilst raising funds for the charities working to help the birds most at need.

This blog is about the nine waders in the book, but there are 58 other fascinating species accounts and wonderful artworks. Each species account starts with a quote from the story in the book and is accompanied by a low-resolution version of the artwork (Ringed Plover is illustrated above).

Lapwing

blog l“It’s the crest that does it for me – that flicked nib stroke, the artist’s afterthought” – Lev Parikian

The Lapwing used to nest across the whole of the United Kingdom and was a common bird in almost every village. It’s still the most numerous breeding wader in the UK, with 97,500 pairs (APEP4), beating Oystercatcher by just 2,000 pairs. Numbers dropped by 54% between 1967 and 2017, according to BirdTrends 2019, published by BTO & JNCC. Huge losses had already occurred over the previous two centuries, as land was drained and vast numbers of eggs were collected for the table. The Lapwing is now a bird associated with lowland wet grasslands and the uplands, rather than general farmland.

Red-listing has been important for Lapwing, increasing the profile of the species and encouraging the development of specific agri-environment schemes targeted at species recovery. These include ‘Lapwing plots’ in arable fields and funding to raise the summer water tables in lowland grassland. Several WaderTales blogs describe efforts to try to increase the number of breeding waders in wet grassland, especially Toolkit for Wader Conservation. The loss of waders, and Lapwings in particular, from general farmland is exemplified in 25 years of wader declines.

Ringed Plover

blog rp graph“They gather at high tide like shoppers waiting for a bus: all facing the same direction, and all staring into the distance” – Stephen Moss

One of the criteria that the BOCC panel takes into account, when constructing the Red List, is the responsibility the UK has for a species or subspecies in the breeding season, during winter or both. The Ringed Plovers we see in the UK in the winter are almost exclusively of the hiaticula subspecies; birds that breed in southern Scandinavia, around the Baltic, in western Europe and in the UK. There are only estimated to be 73,000 individuals in this subspecies, so the 42,500 that winter in the UK constitutes a large percentage of the Ringed Plovers that breed in many of these countries.

The Wetland Bird Survey graph alongside shows a decline of over 50% between 1989 and 2014. At the start of the period, Ringed Plover numbers were at an all-time high but this is still a dramatic and consistent drop. Numbers have stabilised and may even have increased slightly but Ringed Plovers need some good breeding years. Disturbance is an issue for breeding Ringed Plovers, which share their beaches with visitors and dogs, and could also potentially be a problem in the winter (see Disturbed Turnstones).

Dotterel

blog dot“I want you in the mountains. Summer breeze. At home. Doing your thing. So don’t go disappearing on us, okay?” – Fyfe Dangerfield

The Dotterel is a much clearer candidate for Red67 – there’s a small population in a restricted area and numbers have fallen. The detailed reasons for decline may still need to be nailed down but candidate causes such as declining insect food supplies and the increasing numbers of generalist predators are probably all linked to a changing climate – squeezing Dotterel into a smaller area of the mountain plateaux of Scotland.

There’s a blog about the decline in Dotterel numbers called UK Dotterel numbers have fallen by 57%, based upon a paper that uses data up until 2011. At this point, the population was estimated at between 280 and 645 pairs. There has been no suggestion of improvement since that blog was written. Interestingly, Dotterel may have a way out of their predicament, as we know that marked individuals move between Scotland and Norway in the same breeding season.

Whimbrel

blog whim“How often do Whimbrels pass overhead nowadays? Unseen and unheard, their calls mean nothing to most of us” – Patrick Barkham

Most British and Irish birdwatchers think of Whimbrel as spring migrants, enjoying seeing flocks of Icelandic birds when they pause on their way north from West Africa (see Iceland to Africa non-stop). There is a small, vulnerable population nesting almost exclusively on Shetland. The latest estimate is 310 pairs (2009), down from an estimate of 530 pairs, published in 1997. Many pairs have been lost from Unst and Fetlar and this blog about habitat requirements, based on RSPB research, might give clues as to why: Establishing breeding requirements of Whimbrel.

The curlew family is in trouble across the Globe, potentially because these big birds need so much space (see Why are we losing our large waders?)

Curlew

blog cu“… achingly vulnerable in a world that is battling to hold onto loveliness” – Mary Colwell

What more can be said about Curlew, ‘promoted’ to the red list in 2015 and designated as ‘near threatened’ globally. Most significant is the story from Ireland, where 94% of breeding birds have disappeared in just 30 years. These blogs provide more information about the decline and review some of the reasons.

There are more Curlew-focused blogs in the WaderTales catalogue.

Black-tailed Godwit

blog blackw“A glimpse of terracotta is obscured by ripples of grass, dipping gently in the breeze” – Hannah Ward

Winter Black-tailed Godwit numbers are booming but these are islandica – birds that have benefited from warmer spring and summer conditions in Iceland, as you can read here in: From local warming to range expansion. Their limosa cousins are in trouble in their Dutch heartlands (with declines of 75%) and there have been similar pressures on the tiny remaining breeding populations in the Ouse and Nene Washes. Here, a head-starting project is boosting the number of chicks; so much so that released birds now make up a quarter of this fragile population. Red-listing has shone a spotlight on this threatened subspecies, attracting the funding needed for intensive conservation action.

Ruff

blog ruff“They look a bit inelegant – a small head for a decently sized bird, a halting gait, and that oddly vacant face” – Andy Clements

There are two ways for a species to be removed from the Red List – extirpation (extinction in the UK) and improvement. Temminck’s Stint came off the list in 2015, having not been proven to breed since 1993, and Dunlin was moved to Amber at the same time. Ruff are closer to extirpation than they are to the Amber list. There is a spring passage, mostly of birds migrating from Africa to Scandinavia and the Baltic countries, and some males in glorious breeding attire will display in leks.

250 years ago, Ruff were breeding between Northumberland and Essex, before our ancestors learnt how to drain wetlands and define a hard border between the North Sea and farmland. Hat-makers, taxidermists and egg-collectors added to the species’ woes and, by 1900, breeding had ceased. The 1960s saw a recolonisation and breeding Ruff are still hanging on. There are lekking males causing excitement in sites as disparate as Lancashire, Cambridgeshire and Orkney, and there are occasional nesting attempts. Habitat developments designed to help other wader species may support Ruff but the situation in The Netherlands does not suggest much of a future. Here, a once-common breeding species has declined to an estimated population of 15 to 30 pairs (Meadow birds in The Netherlands).

Red-necked Phalarope

blog rnp“… snatching flies from the water in fast, jerky movements, droplets dripping from its slender beak” – Rob Yarham

Red-necked Phalaropes that breed in Shetland and a few other parts of northern Scotland appear to be an overflow from the Icelandic population; birds which migrate southwest to North America and on to the Pacific coastal waters of South America. This BOU blog describes the first track revealed using a geolocator.

The Red-necked Phalarope was never a common breeder and came under pressure from egg-collectors in the 19th Century. Numbers are thought to have recovered to reach about 100 pairs in Britain & Ireland by 1920. Numbers then fell to about 20 pairs by 1990, so the latest estimate of 64 pairs (The Rare Breeding Birds Panel) reflects conservation success. Given the restricted breeding range and historical declines, it is unlikely that the next review will change the conservation status from Red to Amber, despite the recovery of numbers.

Woodcock

blog wk“… taking the earth’s temperature with the precision of a slow, sewing-machine needle” – Nicola Chester

The presence of Woodcock on the Red List causes heated debate; how can this still be a game species? Red-listing is indisputable; the latest survey by BTO & GWCT showed that there was a decline in roding males from 78,000 in 2003 to 55,000 in 2013, with the species being lost from yet more areas of the UK. Each autumn, the number of Woodcock in the UK rises massively, with an influx of up to 1.4 million birds. Annual numbers depend upon seasonal productivity and conditions on the other side of the North Sea. A recent report on breeding wader numbers in Norway, Sweden and Finland, shows that breeding populations of Woodcock in this area are not declining (Fennoscandian wader factory).

The UK’s breeding Woodcock population is under severe threat from things such as increased deer browsing and drier ground conditions but winter numbers appear to be stable. The difference in conservation status between breeding and wintering populations is reflected in the fact that Woodcock is on both the Red List and the Quarry List, for now. There is a WaderTales blog (Conserving British-breeding Woodcock) that discusses ways to minimizes hunting effects on British birds. These guidelines from GWCTemphasise the importance of reducing current pressures on British birds.

In conclusion

blog bookThe Red List creates some strange bedfellows. In the book, Turtle Dove follows Herring Gull; a bird with links to love and romance and another with at best the charm of a roguish pirate. But the List works; it creates an evidence-base that help those who devise agricultural subsidy systems, advise on planning applications, license bird control and prioritise conservation initiatives.

Red67 seeks to raise awareness of the UK’s most at-risk bird species, nine of which are waders, and to raise money for BTO and RSPB scientists to carry out important research. It’s a lovely book that captures the thoughts and images of a generation of writers and artists. You can learn more about the project, order the book and buy some Red Sixty Seven products by clicking here.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

 

Disturbed Turnstones

blog facingIn a 2020 paper, Mark Whittingham and colleagues show that, in one area of northeast England, the decline in Turnstone numbers is more obvious on mainland sites that are subject to human disturbance than on offshore refuges. Whilst national declines are probably linked to factors affecting productivity in breeding areas in Greenland and Canada, it is interesting that Turnstone seem to be withdrawing into areas where they are subject to less winter disturbance.

Turnstones – some background

The Turnstones that we see around the coastline of Britain and Ireland in the winter are almost exclusively birds that fly here from Greenland and eastern Canada, as you can read in this blog about wader migration (Which wader, when and why?). Britain’s wintering Turnstone numbers are falling, as are populations of several other species, such as Curlew, Oystercatcher, Knot and Redshank (see Do population estimates matter?). Turnstones are opportunist feeders; although traditionally thought of as rocky coast specialists, they can also be found on muddy estuaries and around beach-bars in the Caribbean (Why do Turnstones eat chips?).

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Measuring disturbance

Assessing the effects of disturbance during the winter is not easy. Feeding waders may be flushed by bait-diggers, kayakers, dog-walkers etc. but is this an issue if the food that they were attempting to eat becomes available later? To demonstrate that disturbance is a real problem, one would ideally demonstrate reductions in fitness measures such as survival, recruitment and/or productivity. This is discussed in a paper by Jenny Gill and colleagues, who studied the potential effects of disturbance on feeding Black-tailed Godwits (paper in Journal of Applied Ecology) and in another paper by Colin Beale and Pat Monaghan that shows that well-fed Turnstones were quicker to respond to disturbance than birds that had not received supplementary food supplies (Animal Behaviour).  Birds may be quicker to fly if they are well-fed or there is somewhere else where they can feed. The ones that have no choice and are still hungry may be the last to leave. The issue is discussed more widely in Why behavioural responses may not reflect the population consequences of human disturbance.

blog chasing egret

It’s not just waders : Little Egret being chased  along the shores of the River Bann SPA and (below) the last few Brent Geese being removed from saltmarsh on the Exe Estuary (SPA)

Potentially, roosting waders could be more prone to disturbance than feeding birds, because of the wasted energy associated with flying around over the high-tide period or relocating to an alternative roost site (see A place to roost). An interesting modelling paper by Mark Rehfisch and colleagues showed that 90% of Dunlin, Grey Plover and Redshank on the Wash could be serviced by roost sites that were 2 km, 2.5 km and 3.5 km apart, respectively (Applied Ecology). These numbers may or may not be comparable for Turnstone but do suggest that small- to medium-sized waders feed within relatively short distances of their preferred roosting areas.

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Turnstone in this study

Turnstone is a species of qualifying interest for the Northumbria Coast Special Protection Area (SPA) and for several Sites of Special Scientific Interest (SSSI) in the region. On this 140 km stretch of coast, the population of Turnstone declined by 27% between 2004/5 and 2009/10, during a period when the wintering number within England declined by 9%. There was concern that human disturbance may be one of the drivers of the population decline of wintering Turmstone within the SPA. Potentially such conditions could become more challenging towards the end of the winter, when food supplies may be less and birds are preparing for migration, or during periods of very cold weather. Given an increase in the local human (and canine) population and a marked rise in tourism within the region, it was suggested that the potential for disturbance may have increased.

 

study area

The aim of the study was to compare wintering Turnstone densities and changes in counts across time from sites with differing levels of human disturbance. This was possible because long-term Wetland Bird Survey counts of waders had been made in the period between 1998/99 and 2015/16. Counts were available for two offshore refuges and 17 mainland sites that were subject to higher levels of human disturbance. No direct measure of human disturbance was available so questionnaires were used to determine the behaviour of beach users, in terms of distance travelled to visit the coast. The paper contains full detail of this methodology.

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Results

After controlling for the extent of preferred habitat (rocky shore) at each site the authors found that:

  1. The closer each of the 19 sites was to the nearest offshore refuge the higher the density of Turnstones, where density is calculated as birds per hectare of suitable feeding habitat.
  2. Turnstone counts at the four sites closest to, or containing, offshore refuges showed no significant declines. Despite the national decline in the number of wintering Turnstones, the counts on the Farne Islands and on St. Mary’s Island (both offshore islands) rose during the study period, although the rate of increase was not statistically significant from zero. There were declines at 15 of the 17 non-refuge sites. These results are consistent with the idea that, as populations decline generally, the sites of the highest quality (in this case those subject to less human disturbance) will show no, or slower, declines.
  3. 65% of the walkers interviewed on beaches were exercising their dogs, 83% having travelled 6 km or less to get to the beach. No relationship was found between Turnstone counts and human population densities. There is more information in the paper about the amount of time that people spend on different types of beaches.
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Graph showing Turnstone densities at different distances from refuges on the coast of northeast England. Figure from paper in Bird Study.

 

Implications

The authors of the Bird Study paper have not sought to explain declines in Turnstone numbers, but they have provided some useful references in the Discussion that highlight how improved water treatment and warmer winters might have affected regional distributions. They also remind us that Turnstone numbers are declining – as is the case for several High Arctic species. Having established that there are declines, they use the pattern of change to ask questions about whether disturbance is an issue for this species.

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Seahouses, looking out towards The Farnes – not far, as the Turnstone flies

The results of the research suggest that Turnstones make greater use of relatively undisturbed areas (offshore refuges) than those subject to greater disturbance by humans and their four-legged friends. Previous work has shown that excessive disturbance prevents the use of roosts and that disturbance can have serious energetic consequences (see A place to roost). Although the paper does not distinguish between birds that are foraging or roosting, this study suggests greater provision of undisturbed sites (refuges) within, or close to, protected areas is important for Turnstones, especially if there is also a drive to build more houses and attract more tourists.

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Beaches at Seaburn (County Durham) and Ross Back Sands (Northumberland). Proximity to human settlement makes a big difference! There are 15 dogs in the left-hand picture.

When looking at the planning process for developments close to SPAs, Mark Whittingham and his colleagues suggest that three issues need to be considered in some detail:

  1. While it is valuable to consider the SPA as a whole, it is also important for decision-makers to consider the vulnerabilities of constituent parts of the site.  Thus, for planning decisions based upon environmental impact assessments, there is clearly a need to consider pressures on particularly vulnerable areas, e.g. those used for roosting.
  2. blog tagged

    One of the tagged individuals that was tracked as part of a complementary study

    Studying the behaviour of marked individuals might help to pinpoint areas that are of critical importance. A separate, small-sample study of radio-tagged Turnstones in the area showed that these birds avoided mainland feeding and roosting areas at night, with at least some of the tagged Turnstones being found on offshore sites.

  3. Species need to be considered separately when assessing disturbance issues because habitat use and resource distribution varies widely. The focus for Turnstones is on rocky coasts and this determines their choice of roosting sites. The requirements of red-listed Ringed Plover (for instance) may be very different, especially as they spend a lot of time feeding on the sort of open beaches that look great for exercising dogs.

Paper

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Dogs are an important part of the disturbance issue.

The paper at the heart of this blog is:

Offshore refuges support higher densities and show slower population declines of wintering turnstones by Mark J. Whittingham, Ailsa J.  McKenzie, Richard M. Francksen, David Feige, Tom Cadwallender, Matthew Grainger, Nadheer Fazaa, Caroline Rhymer, Catherine Wilkinson, Pauline Lloyd, Ben Smurthwaite, Steve M. Percival, Tammy Morris-Hale, Clare Rawcliffe, Claire Dewson, Sarah Woods, Gavin B. Stewart & Elizabeth Oughton. Bird Study DOI  10.1080/00063657.2020.1713725


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

 

WaderTales blogs in 2019

Nineteen new WaderTales blogs were published during 2019. Click on a link in bold to read an individual blog.

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Ringed Plovers often have time to nest again if the first clutch is lost

Over 25,000 people, representing 130 countries, visited the WaderTales website during 2019.

  • The most widely-read blog was Ireland’s Curlew Crisis, reflecting the international concern for the species and the culew family as a whole.
  • It is great that the next most popular blog is Managing water for waders, as this is such a positive story about how farmers, conservation organisations and statutory agencies can work together to deliver better habitat for breeding waders and an improved water supply for farmers.
  • In third place is Sixty years of Wash waders which describes six decades of scientific outputs of the Wash Wader Ringing Group. The WWRG’s founder, Clive Minton, died in tragic circumstances just a couple of months later and there are some lovely tributes here, on the International Wader Study Group website.

Migration

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The distinctive white under-wing of a Steppe Whimbrel

The migration blogs cover a wide range of species:

  • Generational Change uses colour-ring sightings to explore how Black-tailed Godwit populations have changed in distribution and migratory timing.
  • Whimbrel: time to leave summarises a paper about the consistencies and variability of annual migration patterns of individual Whimbrel.
  • Red Knot pay the price for being fussy eaters discusses the reliance of Delaware Bay birds on the unpredictable annual supply of horseshoe crab eggs. Why are Ruddy Turnstones better able to cope in a changing world?
  • Not-so-Common Sandpipers mixes information about migration with a review of Common & Spotted Sandpipers by Phil Holland.
  • Travel advice for Sanderling summarises research to understand the pros & cons of spending the non-breeding season in widely different locations. Birds in equatorial Africa do far less well than those in England and Namibia.
  • In search of Steppe Whimbrel summarises a paper about two very special individual Whimbrel. Will this knowledge help to rescue a subspecies?

Breeding waders

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Redshanks need long grass in which to hide their nests

There is bad news for Curlew and Redshank, some interesting information about the effects of ticks on chicks and an important stock-take of Fennoscandia’s breeding waders.

  • Redshank – the ‘warden of the marsh’ focuses on Redshank that breed on saltmarshes and the agricultural subsidies that help to fund their conservation.
  • From local warming to range expansion explores the role of climate warming in fuelling the century-long range expansion of Iceland’s Black-tailed Godwit population.
  • 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 the previous 30 years.
  • Chicks and Ticks reviews a study of the effects of ticks on the survival probability of Golden Plover chicks.
  • Fennoscandian wader factory summarises analyses of breeding wader numbers in Finland, Sweden and Norway over the period 2006 to 2018.
  • Managing water for waders celebrates work to reduce flooding, store fresh water for farmers and create habitat for breeding waders.
  • Time to nest again? asks how much of the advantage of being an early migrant could be associated with having an option to nest again, if the first attempt fails.

Winter waders 

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Winter numbers of Oystercatcher and Knot have declined in Britain and Ireland

The Green Sandpiper blog reveals unpublished information about territoriality. The other two blogs in this section summarise population estimates of waders in Great Britain and Ireland, based on new papers in British Birds and Irish Birds.

  • Winter territories of Green Sandpipers includes unpublished information from southern England, where survival is affected by the severity of winters.
  • Do population estimates matter? is inspired by the waders section of Population estimates of wintering waterbirds in Great Britain, based on data from the Wetland Bird Survey and the Non-estuarine Waterbirds Survey.
  • Ireland’s wintering waders complements the above blog, providing information from I-WeBS and WeBS for the island of Ireland and set in a European context.

The others!

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Adding colour rings and individual flags to Grey Plover

One of the aims of these blogs is to engage people in projects that are in need of volunteers or other forms of public engagement – hence the Northern Ireland blog. The other two articles celebrate sixty years of The Wash Wader Ringing Group and share concerns about a new airport for Lisbon, to be built right next to the Tagus/Tejo Estuary.

  • The Waders of Northern Ireland was written as a promotional tool for a 2019 breeding survey but covers wintering and passage species too.
  • Sixty years of Wash waders celebrates the longest-running wader-ringing project in the UK  (and the world?), by summarising six decades of migration research.
  • Tagus estuary: for birds or planes? What could go wrong if an international airport is built right next to an estuary that is important to Black-tailed Godwits?
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Vast flocks of Black-tailed Godwit gather in the Tagus Estuary in February

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.The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published. Full list of blogs here.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

Tagus estuary: for birds or planes?

blog samoucoA planned new airport that will serve Lisbon threatens the future of internationally important flocks of waders and other waterbirds. These same birds pose safety concerns for the passenger aircraft that will fly through the airspace that is currently reserved for them.

The development site of the proposed Montijo airport abuts the part of the Tagus/Tejo estuary that is designated as a Special Protection Area (SPA) and an Important Bird Area (IBA). This designation is based upon counts of 49,000 Black-tailed Godwits, 12,000 Dunlin, 6000 Avocet, 4500 Wigeon, 3300 Greylag Geese, 2000 Grey Plover and 1600 Greater Flamingos. That’s 23 tonnes of birds, representing just a few key species, before you add in gulls, Spoonbills and up to 6,000 Glossy Ibises. This blog focuses upon the importance of the Tagus/Tejo Estuary for just one of the species, the Black-tailed Godwit.

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The planning process

At first sight, turning the air force base in Montijo into a commercial airport looks like an obvious option, given that planes already take off and land there. However, the runway will need to be longer, there will have to be a vast new infrastructure and planes will be landing every few minutes, rather than during scheduled periods of military training. There will be some habitat removal, and it will be hard to avoid run-off of fuel and chemicals into the estuary, but the big problem will be disturbance of the flocks of birds within this IBA, as planes land and take-off and when airport employees frighten away flocks that are too close to the main flight-paths. Each time a flock of birds takes to the air, a large amount of fuel is burnt – as fat laid down for migration is wasted.

blog flamingoPlanes and birds do not mix, as we saw on 15 January 2009, when US Airways Airbus Flight 1549 landed on the Hudson River after an encounter with Canada Geese. How many Greater Flamingos will it take to stop a jet engine? Each one weighs about three kilogrammes and there are 1600 on the SPA, many within a few hundred metres of the airport site.

Around the world, there have been many bird/plane incidents, some causing significant loss of (human) life, which explains why there’s not a ‘Boris Island Airport’ in the Thames Estuary. History suggests that bird-strike risks are underplayed at the planning stage but have to be coped with later. Once the airport is operational, it is likely that nests will be removed and attempts will be made to disperse flocks through disturbance and shooting.

Icelandic Black-tailed Godwits

The Tagus is particularly important for Black-tailed Godwits. Although the published count, associated with the designation of the estuary, is 49,000, it is agreed that the maximum late-winter number for the estuary and surrounding rice fields is now 70,000 or more, which includes birds of both the islandica and limosa races.

mapThere are Black-tailed Godwits on the Tagus during every month of the year. Numbers are lowest in the summer, chiefly comprising young islandica birds that do not travel back to Iceland in their first spring. Adults arrive back from Iceland between July and November, the later birds having stopped off to moult in sites such as the Wash (Eastern England) and coastal France. Numbers drop again as early as January, when adults move to the Netherlands and England, to fatten up for the trip back across the Atlantic to Iceland. There is a blog about this ‘overtake manoeuvre’ and the advantages it confers.

Given that islandica Black-tailed Godwits can spend the winter anywhere between Scotland and the south of Spain, it could be argued that disturbance on the Tagus, to try to disperse flocks, would be no big problem, as there are other places for individuals to spend the winter. Two things are wrong with this theory. Firstly, as was described in Generational Change, individual Black-tailed Godwits are creatures of habit, typically using a suite of about four non-breeding sites during their entire lives. If a Black-tailed Godwit is on a patch of mud in December one year then it will be back there the next year, and possibly for the next twenty.

blog RedshankThere is no reason to believe that Black-tailed Godwits are unique in being site-faithful. In the WaderTales blog called A place to roost there is a description of the consequences of site removal for Redshank in Cardiff Bay. Birds displaced by the flooding of the bay had much lower survival rates in the next year and in subsequent years than other Redshank with which they shared their new winter homes. This illustrates the second point; even though these Redshank were only forced to move a few kilometres, they were still severely disadvantaged.

Limosa Black-tailed Godwits

The Tagus really comes into its own during the late winter, as limosa Black-tailed Godwits pour into the area, en route to their breeding grounds in continental Europe. An increasing number of the limosa subspecies now spend the winter on the estuary and in surrounding fields but numbers grow rapidly in January, as others join them from sites as far south as Guinea, in West Africa. On the Tagus, they moult into summer plumage and build up fat reserves that will fuel flights to The Netherlands and surrounding countries, and prepare them for the breeding season that lies ahead. A favourite rice field may hold up to 70,000 Black-tailed Godwits in late February, which includes half of what’s now left of the Dutch breeding population. This is also where many of the birds that are heading back to the Nene and Ouse Washes of Eastern England fuel up for the final leg of their journeys home. Several of the Project Godwit head-started birds (youngsters raised from eggs and released when just about to fledge) have been seen on the Tagus in February.

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To watch vast feeding flocks of Black-tailed Godwits, or their swirling aerial displays, when disturbed by a hunting Peregrine, is an amazing experience – a highlight for locals and for visiting birdwatchers, who holiday here in late winter and early spring. It’s especially impressive to watch the godwits at dusk, when clouds of Glossy Ibis create a backdrop to the action, as they move off the fields and cross the IBA to roosting islands on the far side of the estuary.

blog take offAs indicated earlier, The Tagus Estuary is designated as an EU Special Protection Area because of its crucial role in the lives of a suite of species, just one of which is the Black-tailed Godwit. Over the last few years, the average peak godwit numbers on the Tagus and Sado Estuaries in Portugal have risen from 44,000 to 51,000, at the same time as the breeding population of the subspecies has dropped rapidly (see this WaderTales blog about 75% drop in Dutch numbers). The Portuguese increase has coincided with a rapid decline in spring totals in Extremadura (Spain).

Without colour-rings, it might be assumed that individual Black-tailed Godwits have changed their migration routes, suggesting a flexible response to changing conditions. This is not the case. In their paper, Generational shift in spring staging site use by a long-distance migratory bird, Mo Verhoeven and colleagues show that nearly all of the older birds stick to the routes that they know, with young birds establishing routes that are more likely to include the Tagus and Sado Estuaries. Western Portugal has become vitally important to limosa Black-tailed Godwits, a subspecies that is in huge trouble and upon which millions of conservation Euros are being spent in The Netherlands and elsewhere.

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What next?

The Portuguese Environmental Agency (Governmental institution) has given the go-ahead for the development of the airport at Montijo, despite robust arguments from researchers and conservationists about the inevitable effects on the IBA, and errors and limitations they have identified within the Environmental Assessment Study. There are also concerns about flooding risk, air pollution and other issues that seem not to have been fully assessed.

AEWASPEA, the Portuguese BirdLife partner, together with wader researchers who have studied waterbirds in the Tagus for decades, have submitted a request to the UNEP African-Eurasian Migratory Waterbirds Agreement (AEWA) to open an Implementation Review Process, to help Portugal to ensure that it complies with its obligations as a signatory to the treaty. The approach to AEWA is particularly appropriate for Black-tailed Godwits, as AEWA has already published a Single Species Action Plan to try to support efforts to restore populations of the rapidly declining limosa subspecies.

Black-tailed Godwits may be the most numerous of the key waterbird species for which the Tagus/Tejo Estuary is designated but let’s not forget the next most numerous six: 12,000 Dunlin, 6000 Avocet, 4500 Wigeon, 3300 Greylag Geese, 2000 Grey Plover and 1600 Greater Flamingos.

flamingo and ibis

Key conservation point

The most important conservation fact to bear in mind is that, as has been shown for Black-tailed Godwits, individual birds tend to be remarkably inflexible. Circumstances determine the migration pattern in the first year of life and, if a bird survives, it will continue to do the same things in subsequent years. Building an airport and then trying to reduce plane/bird interactions will quite probably affect the quality of the IBA for waders and other species. Individuals are unlikely to move elsewhere; they are more likely just to try to cope with altered circumstances. Habitat loss and disturbance on this scale are very likely to result in high levels of mortality and declines in the numbers of birds using this critically important site on the East Atlantic Flyway.

Petition

The Black-tailed Godwit is the Dutch national bird. The BirdLife partner in the Netherlands, Vogelbescherming, has launched a petition to register Europe-wide concern about the Portuguese decision to build the new airport. Not only will the new airport be a disaster for the East Atlantic Flyway, it also sets a precedent for developments affecting other Europe wetlands. Please click here to sign.

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GFA in Iceland

Graham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

Fennoscandian wader factory

 

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Nesting Temminck’s Stint – the smallest of the 22 wader species for which trends are reported

At the end of the summer, vast numbers of waders leave Norway, Sweden and Finland, heading southwest, south and south-east for the winter. In a 2019 paper by Lindström et al, we learn what is happening to these populations of Fennoscandian breeding species, as diverse as Temminck’s Stint and Curlew. The news for the period 2006 through to 2018 is basically pretty good – most populations have been stable and there are even some that have increased – but there are worrying signs for Broad-billed Sandpiper, Red-necked Phalarope and Whimbrel.

Breeding waders of Fennoscandia

blog mapAs a volunteer taking part in the Breeding Bird Survey (BTO/JNCC/RSPB) in the UK, I feel that I do my bit to monitor what is happening to local bird population – providing counts that build into national trends. The work involved in delivering indices for breeding waders across the area of Fennoscandia shown in the map is in a different league. Here, counters visit habitats as diverse as forests, wetlands, mires and tundra, within the boreal and arctic areas of Norway, Sweden and Finland. Some survey sites are so remote that access requires the use of helicopters.

Fennoscandia provides important breeding areas for a large set of wader species, and models suggest that these habitats may be particularly vulnerable to climate change, especially increasing summer temperatures. The 2006-18 analysis in Wader Study, the journal of the International Wader Study Group, presents population trends for 22 wader species. The trends are based on 1,505 unique routes (6–8 km long), distributed over an area that’s about four times that of the United Kingdom. 

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The surveys took place across the whole of Norway and Finland, and in the northern two thirds of Sweden, between 58°N and 71°N, which largely coincides with the boreal, montane and arctic regions of Fennoscandia. The systematic distribution of these routes ensures that the main habitats in these countries are sampled in proportion to the area they cover. The paper describes the methodologies used in the three countries and the way that data were combined, especially factors used to translate sightings of individuals into ‘pair-equivalents’.

Overview of results

blog mountainLooking at the results from across Norway, Sweden & Finland:

  • In terms of pure numbers, Golden Plover was the most commonly encountered wader species, followed by Wood Sandpiper, Snipe, Greenshank and Green Sandpiper.
  • The five most widespread species, seen on the highest number of routes, were Snipe, Green Sandpiper, Greenshank, Wood Sandpiper and Common Sandpiper.
  • Wader species richness and the total number of wader pairs were both higher with increasing latitude; the median number of wader pairs per 10 km increased from just below 3 at latitudes 58–60°N, to just above 26 at latitudes 69–71°N.
  • Using a multi-species indicator, the research team found no general change in wader numbers over the period 2006-18.
  • The trends were significantly negative for three species: Red-necked Phalarope (-7.9% per year), Broad-billed Sandpiper (-5.4% per year) and Whimbrel (-1.3% per year).
  • The trends were significantly positive for three species: Oystercatcher (+4.9% per year), Dunlin (+4.2% per year) and Wood Sandpiper (+0.8% per year).
  • There was no significant trend for another 16 species for which encounters were deemed to be frequent enough for analysis.
  • Population trends of long-distance migrants tended to be more negative than those of medium-distance migrants. This is discussed in detail in the paper.

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Focusing on some key species

The Lindström et al paper is a tremendously rich source of information and references. Here are some species-specific highlights.

Oystercatcher. In the context of a species that is declining across NW Europe, the fact that there is a significant increase in Oystercatchers across Fennoscandia may be surprising. However, the authors note that there was a jump in numbers between 2006 and 2007 with little change since then.

blog l graphLapwing. The trends within the three Fennoscandian countries are very different. In Norway, there has been a dramatic decline (-15.2% per year during 2006–2018) and the Lapwing is now nearly extinct in many areas. The trend in Sweden is also significantly negative (-5.8% per year). In Finland, however, where the species is more widespread and numerous, there has been a strong increase (+5.9% per year) during the same period. See figure alongside.

Golden Plover. No significant change overall. There are some country-specific differences in trends, with a moderate decline in Norway being countered by a moderate increase in Sweden. 

Snipe. The overall trend of this species for each country indicates an initial decline followed by an increase. A similar pattern has been noted in the UK’s Breeding Bird Survey over the same period. 

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Nesting Whimbrel

Woodcock. The trend for 2006–2018 is basically stable and similar in all three countries.

Curlew. There is no significant trend, overall, but populations in Norway and Sweden have declined at the same time that numbers in Finland have increased.

Whimbrel. Fennoscandian trend indicates a decline of 1.3 % per year. Whimbrel is doing poorly in Norway and Sweden but better in Finland. 

Wood Sandpiper. This widespread species has increased slowly (0.8% per year), a trend that is largely driven by Norwegian and Swedish populations.

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Wood Sandpiper was the second most commonly encountered wader

Redshank. The fact that no change was discernible, suggests that boreal and arctic populations are faring much better than the breeding populations further south in Europe. For example, see Redshank – warden of the marsh.

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Redshank – more obvious than most breeding waders encountered!

Spotted Redshank. The estimated annual decline for Spotted Redshank is 2.8% per year but the species is too thinly spread for this to provide significant evidence of a decline. This rate is very similar to the recent drop in the Wetland Bird Survey index in the UK. See Fewer Spotted Redshanks.

Broad-billed Sandpiper. This species has the second most negative trend among the 22 species analysed (-5.6% per year). The bulk of information comes from Finland where the trend is even more negative (-7.5% per year). Birds head southeast in the autumn to countries bordering the Indian Ocean – areas for which winter trend data are not available. The species is still considered to be of ‘least concern’ but perhaps this designation may need to be revisited?

Dunlin. Breeding birds in the survey area are largely of the alpina race. The overall trend is significantly positive (+4.1% per year), which is in sharp contrast to the strong declines of the schinzii subspecies that breeds around the Baltic Sea, western Finland and further south and west in Europe.

blog rnpRuff. There were major declines in the period immediately prior to this review (Lindström et al. 2015) but changes reported here are lower (-2.3% per year) and the decline is not statistically significant.

Red-necked Phalarope. The authors write, “This species has the most negative trend of all the 22 species [-7.9% per year], with most data coming from Sweden. We do not know the cause of this decline but, given that this species shares its south-eastern migration route with Broad-billed Sandpiper, whose population exhibits the second largest decline, the relevant problems might largely apply somewhere along the migration routes”.

Link to Britain & Ireland

As shown in Which wader when and why? there are strong migratory connections between Fennoscandia and the British Isles. Some waders, such as Green, Common and Wood Sandpipers, pass through on their way south in the autumn, whilst many more fly here for the winter, to take advantage of the warmer maritime climate.

Three wader species with particularly strong links between Fennoscandia and Britain & Ireland are still shot and eaten in these islands. Each autumn, large numbers of Woodcock, Golden Plover and Snipe cross the North Sea. It is difficult to ascertain figures for the number that are shot but there is agreement that the vast majority are winter visitors, as opposed to native birds. The results presented in the paper suggest that there have been no discernible changes in the Fennoscandian populations of these three game species in the period 2006-18. Two earlier WaderTales blogs focus on Woodcock and Snipe in Britain & Ireland:

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There has been no significant change in Golden Plover numbers across Fennoscandia

Two WaderTales blogs about wintering waders in Great Britain and the island of Ireland were published in 2019, based on reviews in British Birds and Irish Birds. These were Do population estimates matter? and Ireland’s wintering waders. The six big losers, in terms of wintering numbers in these islands, were Knot, Oystercatcher, Redshank, Curlew, Grey Plover and Dunlin. Knot arrive from Greenland and Canada, with Grey Plover flying from Russia, but it is interesting to think about this Fennoscandian breeding analysis in the context of winter losses of the other four species.

  • Wintering numbers of Oystercatchers have dropped recently in Britain and in Ireland. The population is made up of migrants from Iceland (more about this here), very large numbers from Norway, birds that stay within the British Isles and smaller numbers from other European and Scandinavian countries. Given there is no discernible decline in Fennoscandia, it seems likely that much of the decline can be attributed to a major fall in Scottish breeding numbers (more about this here).
  • Most Redshank wintering in Britain & Ireland are of local or Icelandic origin. Fennoscandian numbers seem to be stable; if there were any changes, these would probably not be apparent in wintering numbers within the British Isles.
  • The Eurasian Curlew has been classified as ‘near-threatened’ and the species is known to be declining in many areas (see this blog about serious problems in Ireland). Ringing shows a particularly strong link between Finland, where breeding numbers seem to be increasing, and Britain & Ireland. The decline in British and Irish winter numbers is probably being driven by lower breeding numbers within the British Isles and in countries such as Sweden, Norway and Poland.
  • There is a theory that new generations of alpina Dunlin may be more likely to winter within Europe’s mainland estuaries, instead of continuing their westward migration across the North Sea. This might explain the apparent anomaly between the 4.1% per annum rise in Fennoscandian numbers and recent winter declines of 3% in Britain and over 20% in Ireland.

Going forwards

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Some of the survey areas were in particularly remote areas

Many of the study squares that were covered during these surveys are a long way from the main centres of human population in Norway, Sweden and Finland. The governments of the three countries are to be congratulated for supporting this important monitoring, which relied on the commitment of hundreds of volunteers. It is to be hoped that these surveys will continue and that further species-focused work will be able to explain some of the differences across Fennoscandia, particularly between eastern and western areas. The rapid declines in numbers of two species that migrate southeast each autumn (Broad-billed Sandpiper and Red-necked Phalarope) highlights the need for better information about what is happening on the flyway linking Fennoscandia with the Arabian Sea and coastal countries of the Indian Ocean.

Paper

Population trends of waders on their boreal and arctic breeding grounds in northern Europe: Åke Lindström, Martin Green, Magne Husby, John Atle Kålås, Aleksi Lehikoinen & Martin Stjernman. Wader Study 26(3)

Click on the title of paper to access it on the International Wader Study Group website. Paper is only available to members of IWSG. If you have read the whole of this blog you’ll probably want to join!

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Nesting Bar-tailed Godwit in smart summer plumage


GFA in Iceland

Graham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.