Mission Impossible? Counting Iceland’s wintering Oystercatchers

If Norwegian Oystercatchers migrate south and west for the winter, how is it that thousands of Oystercatchers can adopt a stay-at-home strategy in Iceland, which lies at a higher latitude than most of Norway?

Braving the cold

As part of a project to try to understand why some Oystercatchers spend the winter in Iceland, when most fly south across the Atlantic, researchers needed to count the ones that remain. Unlike in the UK, where the Wetland Bird Survey can rely on over 3000 volunteers to make monthly counts of waders and waterfowl, it’s tough to organise coordinated counts of waders in Iceland. Winter weather, a small pool of birdwatchers and short days don’t help when you are trying to cover the coastline of a country the size of England.

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Up until 2016, the only winter wader data in Iceland came from Christmas Bird Counts, first run in 1956. These coordinated counts suggested that most Oystercatchers were to be found in southwest and west Iceland, which is also where most birdwatchers live, but with smaller numbers in areas such as the southeast. The maximum number of Oystercatchers found in any one year was 4466 birds but this excluded known wintering sites which were inaccessible or very hard to access. Some contributors to Christmas bird counts live in areas away from the well-populated west of the country, and they provided evidence that there were no Oystercatchers in the north, for instance. This information gave some guidance as to where to look for Oystercatcher flocks but could a small team of researchers and birdwatchers do a complete count of the resident component of the species in the middle of winter?

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Part one of the survey involved a group of well-prepared birdwatchers and researchers spending several days counting Oystercatchers in as many areas as possible of the southeast and in the whole of the west, from the southwest tip of Iceland (where Keflavik airport is situated) through to known wintering locations in the northwest fjords. The north and south coasts could largely be discounted; the north is too cold and the south coast is very barren.

Part two of the survey was carried out by air, allowing the addition of counts of the islands and inaccessible coastal sites in the Breiðafjörður Bay, as well as some key sites in Faxaflói Bay (see map). Flocks of roosting Oystercatchers were usually seen from afar and photographs were used to make counts without flushing the birds.

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Survey results

The ground-based wader surveys were carried out between 28 January and 3 February 2017 and the aerial survey took place on 16 February. In total, 11,141 Oystercatchers were counted, which nearly triples the previous Christmas total. As expected, the vast majority of Oystercatchers were found on wintering sites in SW and W Iceland. Large numbers of birds were found on sites not covered by the Christmas counts, particularly on the north side of Faxaflói Bay and during the aerial survey over Breiðafjörður Bay.

blog BoddiThe full results of the paper are presented in a new paper in the BTO journal Bird Study. (Click on title for link)

Population size of Oystercatchers Haematopus ostralegus wintering in Iceland Böðvar Þórisson, Verónica Méndez , José A. Alves, Jennifer A. Gill , Kristinn H. Skarphéðinsson, Svenja N.V. Auhage, Sölvi R. Vignisson, Guðmundur Ö. Benediktsson, Brynjúlfur Brynjólfsson, Cristian Gallo, Hafdís Sturlaugsdóttir, Páll Leifsson & Tómas G. Gunnarsson.

Resident or migrant? 

One of the key questions that researchers wanted to answer was ‘what proportion of the Icelandic breeding population is migratory?’ This is part of a bigger project exploring the causes and consequences of individual migratory strategies, as you can read in the previous WaderTales blog: Migratory decisions for Icelandic Oystercatchers. This project is a joint initiative by the universities of Iceland, East Anglia and Aveiro, led by Verónica Méndez.

blog familyIn order to estimate the proportion of migrants and residents it was necessary first to determine the total size of the Icelandic Oystercatcher population, based on a recent estimate of 13 thousand breeding pairs (Skarphéðinsson et al. 2016) . How many sub-adults are there to add to the 26,000 breeding birds?

Verónica Méndez and her team have shown that Oystercatchers fledge on average about 0.5 chicks per pair. Using estimates that 50% of these chicks are alive by mid-winter, that there is then a 90% chance of annual survival and birds typically breed when they are four years old, it was possible to come up with a total population of just over 37,000 birds.

Although the authors of the paper have produced the best winter estimate thus far, they note that it is a minimum – there could be small numbers of birds in other areas. At 11,141 out of 37,177 birds, the minimum estimate of the residential part of the population is 30%, leaving 70% to be distributed around the coasts of the British Isles and (in smaller numbers) along the coastline of mainland Europe.

Latitudinal expectation 

blog ringed birdTo put the migratory status of the Icelandic Oystercatcher into context with other Oystercatcher populations breeding in NW Europe, the authors collated information about the proportion of resident and migratory Oystercatchers in coastal countries between Norway and the Netherlands. They show that there is a strong latitudinal decline in residency. From Northern Norway (69.6°N) to Southern Sweden (57.7°N), where mean January temperatures are typically in the range of -1 to -4°C, only occasional individuals are found in winter, whereas populations in Denmark (55.4°N), where mean January temperatures 0.8°C, and sites that are further south and warmer mostly comprise resident individuals.

blog scenicThis cline in migratory tendency is also seen within the British Isles, which stretch from 60.8°N to 50.2°N. Writing in the BTO’s Migration Atlas, Humphrey Sitters reports that birds from the north of the British Isles have a median recovery distance of 213.5 km, whereas in the west, east, south and Ireland the respective figures are 35.5, 27.0, 6.0 and 13.5 km. In each group, there are birds that travel over 800 km, implying some degree of migratory tendency in birds breeding in every part of the British Isles.

Iceland lies between 63.2°N and 66.3°N, which puts it well within the latitudinal range of the ‘almost-all-migrate’ group of Scandinavian birds. The Icelandic proportion of 30% residency is likely to be a function of the temperature and geographical isolation of the island. Bathed by the relatively warm waters of the Gulf Stream, some coastal areas, particularly in the west of Iceland, provide a relatively mild oceanic climate and apparently ample food stocks to support high survival during most winters. On the other hand, days are very short. For an Oystercatcher that spends December in Reykjavik, the time between sunrise and sunset is just four hours and the average January temperature is -0.6°C. For a bird in Dublin day-length figure is almost twice as long, at seven and a half hours, and temperature is 5.3°C. Food availability may well be compromised by the time available to collect it, as previous studies have shown that feeding efficiency is on average lower at night.

blog of other wadertalesIceland might hold a higher proportion of residents than would otherwise be the case as it is far enough away from Britain (about 750 km to mainland Scotland) and Ireland for the sea crossing to potentially be a significant barrier. For migrants, time will need to be spent acquiring the reserves needed for the journey south in the autumn and north in the spring and the flights may well add costs in terms of survival probability.

There is a blog about the broader project to understand how individual birds become ‘programmed’ to be migrants or residents here: Migratory decisions for Icelandic Oystercatchers.

The migration option 

blog sightingsIf 30% of Oystercatchers are staying in Iceland this implies that up to 26,000 birds of Icelandic origin are to be found in the British Isles and on the western coast of Europe during the winter. Some of these – young birds that are yet to breed – can be found in these areas in the summer too. By the end of the summer of 2017, Verónica Méndez and her team had colour-ringed about 800 (500 adults, 300 juvenile) birds in Iceland, in order to try better to understand the reasons for the migratory/residency decisions that individuals make. Every dot on the map alongside (which was created on 1st June 2018) represents a migratory bird. Each record is valuable and there are lots more birds to try to find! Are there really no Icelandic Oystercatchers in the vast flocks of eastern England?

If you come across a colour-marked Oystercatcher, please report it to icelandwader@gmail.com 

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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.

 

 

 

 

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Site-fidelity in Black-tailed Godwits

Shorebirds are generally philopatric (site-faithful to breeding areas) – youngsters settle to breed in areas near where they were raised and adults don’t move far in subsequent years. What happens to this process when a species is expanding its range or if chicks are reared away from their parents?

Successful head-starting

In a recent trial, to see if head-starting might help to secure the future of limosa Black-tailed Godwits in the Washes of Eastern England, one of the questions to be answered was “would youngsters reared in captivity be able to gather all of the information they need to return to the same area to breed?”

blog nestEggs collected from nests on the RSPB’s Nene Washes nature reserve were taken to the WWT’s facilities at Welney, about 35 kilometres away, to be head-started. Here, the eggs were hatched and the chicks were raised in captivity. As they got bigger, the birds were colour-ringed and moved into a large pre-release cage before being given their freedom, when old enough to fly. With 26 successful head-started chicks, this process added far more young Black-tailed Godwits to the local population than birds in the wild could manage, subject as they were to predation and to flooding of nests. You can read more on the Project Godwit website and in this WaderTales blog Special Black-tailed Godwits.

Limosa Black-tailed Godwits migrate south for the winter, most flying to countries such as Senegal in West Africa but with an increasing number short-stopping in Spain and Portugal. (There’s a blog about the wisdom of crossing the Sahara).

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In this picture of three head-started chicks, Remi is the chick on the right

As birds moved north in the spring, Project Godwit staff were on the look-out for the previous year’s chicks. They were overjoyed when the first of these appeared at Welney, as had been hoped and might be expected, but puzzled when the second was sighted in Doel, near Antwerp in Belgium, showing signs of pairing with what was assumed to be a local, unringed male. So, what had happened to site-fidelity? Why had this colour-ringed female, named Remi, decided to settle over 300 km away? What are the implications for the project to boost the East Anglian population?

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Sites mentioned in this blog. Remi was collected (as an egg) in the Nene Washes, raised at Welney and turned up next spring in Doel, Belgium. Friesland is Roos Kentie’s study area (see below).

Philopatry in Black-tailed Godwits

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Manea – all grown up and back on the Ouse Washes

The head-starting team had been fairly confident that site-fidelity would ensure that head-started birds would recruit locally, as long as the hand-rearing process did not mess with the innate processes that initiated recruitment.

A paper based on ringing recoveries of the limosa subspecies in The Netherlands, published in 1998 by Kruk et al, suggested that young Black-tailed Godwits tend to settle to breed close to where they previously fledged, with most moving no further than 6 km and no appreciable difference between the sexes.

Natal philopatry in the Black‐tailed Godwit L. limosa limosa and its possible implications for conservation, Ringing & Migration, 19:1, 13-16, DOI: 10.1080/03078698.1998.9674156

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The expanding range of breeding Black-tailed Godwits within Iceland

In Iceland, where the islandica population of Black-tailed Godwits breeds, colour-ringing of chicks has also allowed dispersal patterns to be measured. Here, youngsters of the islandica race are still pretty site-faithful but there are appreciable differences between the two sexes, with some females dispersing far more than males. In their paper published in 2011, Tómas Gunnarsson et al found that males dispersed an average of 2.3 km (with a range of distances of 0.5 to 7 km) and females dispersed an average of 48 km (with a range of 1 to 204 km). As has been discussed in a previous WaderTales blog, Icelandic Black-tailed Godwit numbers have been increasing for a century, with birds moving into new breeding areas further away from the heartlands of the south coast. Dispersal is a necessary part of the expansion process. There’s more detail here:

Rapid changes in phenotype distribution during range expansion in a migratory bird. Proc. Royal Soc. B, 279:1727 (2011). DOI: 10.1098/rspb.2011.0939

postThe conservation problems being faced by limosa Black-tailed Godwits have spawned a lot of recent research in The Netherlands and along the subspecies’ annual migration route (see Dutch Black-tailed Godwit numbers down by nearly 75%, for instance). In a recent paper, Roos Kentie showed that three-quarters of the adults in her Friesland study site in The Netherlands breed within 500 m of their previous nest site, with a maximum movement of 15 km. Having successfully fledged and migrated south and then north, new recruits settled within 18 km. As in the previous paper about the limosa subspecies, there was no discernible difference between the distances moved by males and females, but there were differences in mean dispersal distances of youngsters raised in different habitats. Birds hatched on grass monocultures moved about twice as far as those from herb-rich meadows, but the mean distances were only 915 m and 1700 m for the two habitats. Young birds moved at a higher rate from the predominant monocultures to meadows than the other way around.

Age-dependent dispersal and habitat choice in black-tailed godwits across a mosaic of traditional and modern grassland habitats Journal of Avian Biology 45: 396–405 (2014). DOI: 10.1111/jav.00273

If limosa Black-tailed Godwits recruit to local sites then what was Remi, the head-started bird from the Washes of eastern England, doing in Belgium? Does this failure to be site-faithful impact upon the conservation programme that aims to boost local populations through hand-rearing and releasing chicks?

Back to the Belgian defector

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Protecting nesting waders by setting up electric fences

By early May, five of the Project Godwit head-started Black-tailed Godwits (three males and two females) had been seen on the Ouse Washes, at Welney and other sites. This was excellent news and in line with what might be expected, given that the Dutch study has shown that only 30% of recruitment is in the first summer, with most birds not starting to breed until their second year. No birds had returned to the Nene Washes, where these eggs had been laid. In terms of site-fidelity, this is what had been expected. It was great news; head-starting works and can give a conservation boost for the species in areas where insufficient young are produced to maintain local populations. It may therefore be possible to reintroduce (or even introduce) Black-tailed Godwits to suitable sites, simply by releasing hand-reared fledglings when they are ready for their independence.

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The Nene Washes

And then came number six. On 6 May, another of the ringed, head-started birds was seen on the Nene Washes, just a short distance from where the eggs had been collected. She was ‘home’ but did not know it, having been transported 35 km to Welney when in the egg. Amazingly, this bird turned out to be Remi, the female that had been consorting with a male in Belgium three weeks earlier. She was with an unringed male, a bird that members of the Project Godwit team felt looked ill-at-ease, not as accepting of their vehicles as were local birds. Perhaps Remi had acquired her mate in Belgium and brought him with her to England? If so, wouldn’t that be a result – this head-started Black-tailed Godwit had not only returned to breed but she might also have brought an extra bird with her!

Remi's chicks

In terms of site-fidelity, Remi fits with the patterns discussed above; she has not moved very far from the site she knew as a fledgling, as suggested by the studies of limosa birds, but she has dispersed further than any of the males, in line with the islandica study. It will be interesting to see what happens to subsequent groups of head-started birds.

** Fantastic update from Project Godwit **

“Delighted to share news that Remi, released last year at WWT Welney, now has chicks of her own at RSPB Nene Washes! Godwits don’t usually breed in their first year and we hope this is the first of many” 14 June 2018

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For the latest news of the head-starting project, check out projectgodwit.org.uk or follow @projectgodwit on Twitter.


 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

 

 

Curlew Moon

In deference to the scientific papers that underpin them, stories in previous WaderTales blogs are expressed in facts and correlations, not emotions. This blog, which is in part a review of Curlew Moon by Mary Colwell, is a little more personal.

Curlew Moon – a special book

book coverCurlew Moon, is based upon Mary Colwell’s walk from the West of Ireland to the East of England, raising money for the BirdWatch Ireland, BTO, RSPB and GWCT Curlew appeals and researching material for the book. She takes the reader into the stripped-bare peat bogs of central Ireland, shares the excitement of feeling the beating heart of a newly-ringed Curlew and meets some great people who care about Curlews in their own, local patches. The book is a fascinating blend of Curlews, agricultural history, culture and poetry – written beautifully.

Global problems

blog flightCurlews are large waders that live long lives. The family to which they belong, the Numeniini, is not coping well with the speed with which the world is changing. Two species of curlew are probably extinct – functionally if not actually – and the godwit members of the family are faring little better. The blog Why are we losing our large waders? summarises an excellent review by the BTO’s James Pierce-Higgins and colleagues from thirty other organisations/institutions around the world. In it, they assess the stresses that humans are imposing upon curlews & godwits, through direct activities and the impact we all have on the climate. It’s not just our Eurasian Curlew that we need to worry about.

British breeders and foreign visitors

Mary’s walk from west to east began on 21 April 2016, so the bulk of her story focuses upon the Curlew breeding season. The book, however, starts with a couple of trips to see flocks that consist mostly of wintering birds, in Norfolk and the Moray Firth.

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The Wash estuary, the bite out of the east coast of England, between Lincolnshire and Norfolk, holds up to a quarter of a million waders in some months, with a peak annual count of 8,000 or so Curlew. Mary went to Snettisham to see some of these Curlews for herself. Most of the birds had crossed the North Sea in the autumn, from countries such as Finland, Germany and even Russia. There are British-bred birds here too but these are in a minority. The WaderTales blog Is the Curlew really near-threatened? is also rooted in Norfolk. If a Curlew can live for 32 years and there are flocks of 1000 in Norfolk, why are they red-listed as a species of conservation concern?

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Tagging a Curlew: Mary Colwell, with Ron Summers of the Highland Ringing Group

Mary’s next trip was to the Moray Firth, where she met up with members of the Highland Ringing Group. Here, Bob Swann and his colleagues caught eight Curlew, in a mixed cannon-net catch of waders and gulls. I love the way that the strange activities of these dedicated, well-trained volunteers are described! The Curlews were all fitted with geolocators, to track their movements over the next twelve months. A previous bird had revealed a fascinating journey to Sweden and back, with only 53 days on her breeding grounds. She spends by far the largest part of each year in Scotland. What will these new birds tell us about the lives of our largest waders?

Habitat and predators

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An Irish marsh, freshly prepared for the peat-cutting machines

The long walk started in Ireland, where breeding Curlew are closest to extinction. In the Irish Republic, the latest survey revealed a breeding population of 124 pairs, down from perhaps 4,000 pairs in the 1980s. I had read about the causes of the demise of the Irish Curlew but Curlew Moon helped me to understand them. I could hear the silence that made an old man cry, I could see the rows of peat-devouring machines and I could understand the impact of changing farming methods. There may have been economic benefits (for some), associated with funding from the EU and the cessation of the Northern Ireland troubles, but Curlews have not been able to keep up with the changes that prosperity has delivered.

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Curlew nest, tucked away in some long grass

The situation is not dissimilar on the other side of the Irish Sea. In a paper reviewing associations between Curlew numbers in Britain and changes that may be causing them, Sam Franks and BTO and RSPB colleagues conclude that Curlew are less numerous and have shown greater population declines in areas with more arable farming, woodland cover and higher generalist predator abundance. Putting it simply, the key thing that conservationists should focus on are “habitat restoration and reducing the negative impacts of predators”. There’s more about this in Curlews can’t wait for a treatment plan.

blog chickIn the book, Mary describes the disappointments experienced by the Curlew Country team in Shropshire; in the years 2015 and 2016, 32 nesting attempts yielded no fledged chicks. Foxes were the main problem – with additional pressure from other predators and farm machinery. There was better news in 2017, perhaps associated with more fox control; three chicks were raised naturally and others were head-started. By taking ten eggs at the point of laying, replacing them with dummy eggs, and switching again at the point of hatching, the team increased the total number of fledged chicks to eight. After two blank years, this was an encouraging success for the team.

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Grouse

Much has been written about grouse moors and waders. As Mary moved on towards the Staffordshire Moors and then The Peak District she knew that she would “come face-to-face with some of nature conservation’s most bitter conflicts”.

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Curlew, nesting in the short grass on a grouse moor

I shall not attempt to summarise the Curlews and Controversy chapter – read it for yourself – but Mary, who describes herself as “left-wing, vegetarian with vegan tendencies” and who has never even held a gun, found more Curlew on a grouse moor she visited in early April than anywhere on her walk.

By removing predators, burning heather to encourage new growth and keeping trees at bay, shooting estates create habitat that is good for both Red Grouse and Curlew. It also suits Hen Harriers which feed on the youngsters of both species. And that’s when the potential for conflict really starts!

One of the arguments in favour of grouse shoots is a financial one. If there is no shooting, land-owners are going to want a return on their investments and an obvious replacement is serried rows of non-native forestry. This will not only take away moorland but will also have effects beyond the woodland edges, due to the actual and perceived risks of predation.

Making space

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Mary with Neal Warnock of RSPB Northern Ireland

There are conversations to be had about how space can be made for Curlews in upland farms and moors, while enabling these areas to be farmed profitably, or at least without loss. As Mary points out, if one farmer is being compensated for managing land in ways that suit breeding waders, the chance of success becomes vanishingly small if a neighbour receives subsidies to grow carbon-capturing trees. How can we ensure that planners understand the bigger picture?

Curlews need plenty of space and three WaderTales blogs talk about how farming and habitat heterogeneity might be impacting upon their success.

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Rachel Taylor, downloading data from a tracking station

In Curlew Moon, Mary writes about a day in Migneint moor, which lies to the south of Mynydd Hiraethog (mentioned above). Here, she and Rachel Taylor of BTO Cymru went in search of tagged Curlews that are contributing to a study Rachel is running with Steve Dodd of the RSPB. Four males have revealed the scale at which the species operates – “One bird flew a staggering 21 km away to a favoured feeding spot”. A paper in Wader Study by Steven Ewing and colleagues suggests that birds are highly variable in the way they use the landscape; two of their males travelling 1.6 km each evening but one bird staying close to the nest. Curlews need more space than perhaps we appreciated.

The people who care

In researching for her new book, Mary Colwell seems to have learnt as much about the people who study and love Curlew as she has about these special birds.  From her close encounters with cannon-netters, using geolocators to chart Curlews’ movements, through to gamekeepers who control predators, Tom Orde-Powlett managing a grouse shoot and others who are improving breeding habitats and monitoring nesting success, she focuses upon the respect so many people have for this fast-disappearing species. At the same time, she shares her own passion for this emblematic bird, the haunting calls of which echo across too many abandoned moors.

The Book

Curlew Moon is published by William Collins. ISBN 978-0-00-824105-6

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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

 

 

Green Sandpipers and Geolocators

In a paper in the BTO journal, Ringing & Migration, Ken Smith and his collaborators review how wearing a tag, attached using a harness, affects the preening and feeding behaviour of Green Sandpipers. What did they find and where do their Hertfordshire birds spend the summer?

The lives of Green Sandpipers

Tom SpellerAccording to BirdLife International’s Data Zone page, there are between 1.2 million and 3.6 million Green Sandpipers across Europe and Asia. The breadth of this estimate reflects the difficulty of assessing the population of a species that breeds in wet forest clearings, from western Norway to about 155 degrees east in Russia. It’s hardly any easier to count them in the winter, sprinkled as there are around small pools, in ditches and along river valleys from West Africa to Japan.

The occasional pair of Green Sandpipers breed in the UK and Population Estimates of Birds in Great Britain and the United Kingdom, published in British Birds by Andy Musgrove at al suggests, that fewer than 1000 birds spend the winter here, although rather more are seen on passage between Scandinavia and Africa. In an ever-changing world, studying populations of a species that is at the edge of its range has the potential to explain patterns of loss (or gain) that are less obvious in the heart of a species’ distribution.

Why use geolocators? 

In a previous blog (Bar-tailed Godwits: migration & survival), it was shown that colour-rings, which enable individual recognition of a bird without capture, provided 30 times as much information about annual survival as a metal ring. Adding a geolocator takes you into a new data-rich environment. A geolocator is a small device that records the location of an animal. By recapturing a bird a year after ringing and downloading these data, important information about the timing of migration, the duration of stop-overs at fuelling sites and the exact breeding and/or wintering location can be ascertained.

One of the important things to appreciate about scientists who study bird migration is that they are as keen as any other birdwatcher to ensure that the tracking devices they use cause as little disturbance to the normal life of their study birds as possible.

Attaching geolocators

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Geolocator with a light-stalk

In shorebird research, the most common form of geolocator is one that is attached to a ring on the bird’s leg. For most individuals, these devices do not have any negative effects but for smaller waders there can be some problems. Shorebird ecologists from around the globe cooperated to review these issues , publishing it in Movement Ecology. It is summarised in the WaderTales blog, Are there costs to wearing a geolocator? Hopefully, anyone contemplating a new shorebird study will read these before starting. Any data that are collected are only valuable if the birds are either unaffected by the equipment and attachment methods or, if there are effects, these do not prejudice the scientific integrity of the study or the welfare of the birds.

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GPS geolocator, fitted with elastic loops to form the harness

In this study, the Green Sandpipers were fitted with leg loop harnesses, first described by Rappole and Tipton, the authors having decided that ring-mounted geolocators might be too bulky on such a small wader. These harnesses are looped around the top part of a bird’s legs so that the geolocator sits like a small rucsac on the lower back, nestled in the feathers. In the figure below, the left picture shows a tagged bird; you may just make out a slight lifting of the back feathers over the top of the geolocator light stalk. The right-hand picture has been annotated to show how the ‘rucsac’ is fitted.

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The geolocators and harnesses represented 1.4–1.6% of the body mass of the birds. In the study, two different types of device were used, light-level geolocators and GPS geolocators – see the details in the paper. The effects of tagging on behaviour patterns have been examined and written up as a paper in the BTO journal Ringing & Migration, using data collected from seven Green Sandpipers that were fitted with harnesses.

Feeding and preening behaviour

Ken Smith and his colleagues have been studying the Green Sandpipers wintering at Lemsford Springs Nature Reserve in Hertfordshire, southeast England for over thirty years. These shallow lagoons were previously managed as watercress beds. In this particular investigation, the scientists compared the behaviour patterns of individual birds fitted with geolocators, before and after tagging, with a control group of untagged birds. They were particularly interested in the proportion of time spent feeding and preening. Feeding time was thought to be an indication of normal foraging behaviour and preening would be an indication of any discomfort or unfamiliarity caused by the tags and harnesses.

lemsford

Green Sandpipers spend their time feeding, preening and roosting, with most of the feeding activity occurring in loosely defined territories. Four of the tagged birds could be viewed regularly and their activities were observed alongside seven untagged (but colour-ringed) individuals. The amount of time spent feeding increased as days lengthened in the spring and birds prepared for migration. Previous research has shown that the Green Sandpipers on this site are not constrained by feeding opportunities, except in the coldest of condition. In these latter circumstances birds will also feed at night but normally they only feed during the day.

Investigating tag effects

Picture1Lemsford is a well-watched site. Most birdwatchers couldn’t tell which birds were tagged and which ones were not. The tags were so well preened into the plumage that they were extremely difficult to see, even in high-quality photographs. The tags could only be spotted by experienced observers and tag-effects could only be established using 20,000 minutes of observations. A less-intensive study would have showed no significant effects. These bullet points summarise more detailed findings in the paper:

  • All four tagged birds that were closely observed in this study returned successfully from their breeding areas and three of the tags were retrieved. There were no apparent signs of any problems such as skin abrasion or feather wear, caused by the tags or harnesses, and the birds continued to be observed after their tags were removed. The one bird that evaded capture and whose tag was not retrieved was present throughout the second winter.
  • Within the wider group, eight out of ten birds with tags returned the next winter, which is not significantly different from the overall return rate for untagged birds.
  • Tagged birds spent a small but significantly higher percentage of their time preening than untagged birds (untagged birds 4.6%, tagged birds 6.3%). Comparing the periods immediately before and after tagging for the four tagged birds for which detailed observations were collected, there were no differences in the time spent feeding but a significantly higher proportion of the time was spent preening (rather than just resting).
  • Birds may well get used to their tags over time. Of the three tagged birds for which there was sufficient data, two showed significant declines in the proportion of time spent preening over time (15% down to 5%), whereas one was at 6% throughout.

Where do these Green Sandpipers go?

Colour-ringing at Lemsford had already shown that birds are very site-faithful during the winter, once autumn passage birds have moved through. There’s more about this in a previous paper in Bird StudyHabitat use and site fidelity of Green Sandpipers Tringa ochropus wintering in southern England.

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This map is available from the BTO website

At the time that the Migration Atlas (Movements of the Birds of Britain & Ireland) was written, using data collected between 1909 and 1997, there was only one record of a BTO-ringed bird in its breeding area. That bird was found in Sweden, and there has been one other in Finland since. Green Sandpipers are not easy birds to observe and, although the long-term colour-ringing project at Lemsford Springs has generated large numbers of local re-sightings, there have been none elsewhere. Early results from the geolocator study show that the Lemsford wintering birds breed in Norway (2), Sweden (3) and Finland (1). A paper will be produced once a larger sample of results is available for analysis; it will look at migration strategies as well as breeding locations.

There is a WaderTales blog that summarises migration of over 40 wader species to, from and through Britain & Ireland: Which wader, when and why?

This paper

Neil Beadle - twoAlthough this study has involved small numbers of tagged and untagged birds, it has shown a consistent pattern of increase in the proportion of time spent preening by birds after tagging, with some evidence that this subsequently decreases over time. There is no evidence of an adverse impact on return rates of tagged birds from one winter to the next, although with such small sample sizes only a major change would have been detectable.

This paper is published in the BTO journal, Ringing & Migration:

The effects of leg-loop harnesses and geolocators on the diurnal activity patterns of Green Sandpipers in winter Ken W. Smith, Barry E. Trevis and Mike Reed


 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

 

 

Just one Black-tailed Godwit

When you receive a list of sightings of a colour-ringed bird that you have reported to a scheme organiser, it can hide a wealth of information. Here’s one such bird.

Blue Red – Yellow Green-flag

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BR-YGf photographed in Caithness (north of Scotland) in the spring of 2017

There are some colour-ringed Black-tailed Godwits that have generated two hundred or more sightings at well-watched locations but BR-YGf is more typical. When seen in Cambridgeshire on 26 March, that was only the 12th observation in the database.

The Black-tailed Godwit that was soon to become BR-YGf was wintering in Portugal when caught in a mist net, by José Alves and a team of other ringers, just before dawn on 25 October 2014. It was given a unique set of three colour-rings and a flag that would enable it to be identified in the field by birdwatchers. Measurements of wing length and bill length, taken at the time, meant that it could be identified as a male, using criteria described in this paper in Bird Study.

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Wader-ringing team in Portugal

Colour-ringing of Black-tailed Godwits started in Portugal in 2006, when José was working on a PhD at the University of East Anglia, in which he studied the ecology of Black-tailed Godwits wintering on the Tagus and Sado Estuaries of Portugal. Colour-ringing has continued since, contributing to coordinated studies of Icelandic Black-tailed Godwits in Spain, Portugal, France, the UK, Ireland and, of course, Iceland.

Breeding in Iceland

Almost all of the islandica Black-tailed Godwits breed in Iceland, with small numbers on the Faeroes, a handful on the Lofoten Islands of Norway and an occasional breeding pair on a Scottish island. Jenny Gill and I saw BR-YGf in the west of Iceland in April 2016, as we checked for marked birds in a flock of 1100 birds, many of which were new arrivals. He was feeding in a newly-ploughed cereal field, that had been previously spread with pig-muck from the neighbouring industrial-scale piggery. We managed to look at 800 pairs of legs in that flock; there was another green-flagged bird from Portugal, two orange-flags from France, a bird from Ireland and three from England.

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The history of BR-YGf since he started wearing coloured rings in 2014

We have been checking flocks of Black-tailed Godwits arriving in Iceland for many years. One of the most significant recent outputs is a paper that explains that young birds, recruiting into the population, are driving the advancing arrival of the species into Iceland in spring. The results are summarised in this blog: Why is spring migration getting earlier?

Autumn moult

Most of the Icelandic Black-tailed Godwits that winter in Portugal stop off to moult en route in autumn. We see some of these birds in the UK but BR-YGf is one that, from the sightings in September 2016, probably moults into winter plumage in France. Moulting is an energetically expensive process; birds that are mid-moult don’t usually migrate so these autumn staging sites are very important to the flocks that use them. When first caught in Portugal, in late October 2014, BR-YGf was in full winter plumage, probably having recently arrived from France.

Spring overtake

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The Samouco salt-pans, where BR-YGf was ringed, with Lisbon in the background

Portugal is a warm place to spend the winter, with relatively long days and plenty of food – very different from the east coast of England, for instance. The only down-side is that Portugal is a long way from Iceland, which you might think leads to later return in the spring. Most Portuguese birds get around this problem by migrating in two legs, the first of which takes them to either the Netherlands or the British Isles. This blog explains this migratory strategy: Overtaking on migration.

BR-YGf has been spotted in two springs since ringing. On 14 March 2016 he was seen at Old Hall Marshes in Essex by Steve Hunting and on 26 March 2018 he was seen by the Project Godwit team on the Nene Washes in Cambridgeshire. Mark Whiffin and colleagues were looking for limosa subspecies godwits, newly returned from Africa to breed, but their birds were outnumbered by large flocks of islandica, fattening up for the trip north. There’s more about the differences between the two subspecies in Godwits in, godwits out: springtime on the Washes with some hints on distinguishing which is which.

Portuguese birds, on an earlier migratory schedule, tend to be further ahead in terms of moult, standing out in their red finery against the greyer local birds, some of which will travel to Iceland up to four weeks later. You can read more about the spring moult in this WaderTales blog: Spring moult in Black-tailed Godwits. Did you know that waders smell different in summer plumage?

Why Caithness?

BR-YGf has been following a well-used migration route: breed in Iceland, moult in France, winter in Portugal, spring in England, back to Iceland and repeat, for perhaps twenty or more years. What was he doing in Caithness, in the very far north of Scotland on 22 April 2017?

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Although the average timing of arrival of individual godwits in Iceland has not changed, the small amount of annual variation in their timings may be related to the weather they encounter en route. In the spring of 2017, we were in Iceland waiting for birds to turn up. The weather was lovely – if cold – but northerly winds appeared to bring a brief halt to most migration. In our two-week stay we saw only 28 colour-ringed Black-tailed Godwits; not quite as bad as the spring of 2013, when winter returned to Europe in April, but close.

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In some years, Black-tailed Godwits, and other waders making the trip to Iceland, may get part way across the Atlantic and have to turn back or they may reach the north of Scotland or the Western Isles and stop. Colour-ring sightings alert colour-ring coordinators to these events, as presented in the blog: Waiting for the wind.

Thank you

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Looking for Black-tailed Godwits in Moita (Portugal) – José Alves, Jenny Gill and me

Thousands of birdwatchers have contributed to the studies of Icelandic Black-tailed Godwits. Every sighting is valuable, especially repeat records from the same site. This WaderTales blog tells the stories of some of the birdwatchers who contribute their sightings to these projects: Godwits and Godwiteers.

It’s great to see old friends, when out ‘godwitting’. Jenny Gill and I have seen BR-YGf in Portugal (2016 & 2017) and in Iceland (2016). We recognised him but he probably will not have recognised us.

Please report any colour-ringed Black-tailed Godwits to j.gill@uea.ac.uk and she will forward them to the appropriate coordinator as necessary. Thank you!


 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

 

Measuring shorebird survival

BlogRPOver the last fifty years, a range of methods have been used to estimate the annual survival rates of waders/shorebirds. These estimates are based on many hours of patient catching and colour-ring reading, making each one too valuable to discard. How can estimates generated in different ways be combined and what can these estimates tell us about the way in which survival rates vary between species and in different parts of the world?

Survival rates are important

As revealed in this previous WaderTales blog, Waders are Long-lived Birds, larger species survive for 30 years or more and even smaller species, such as Ringed Plover (right), manage 20 years. With relatively low annual breeding productivity, maintaining a high survival probability of typically between 70% and 90% per annum is essential for population stability. If the annual survival figure for adults drops, as discussed in this blog, Wader declines in the shrinking Yellow Sea, this can have rapid and serious consequences for population levels.

BlogYellowSea

Different survival measurements

Cups, ounces and grams; Celsius, Fahrenheit and gas mark; if we all used the same measurements and systems when cooking, life would be much simpler. It turns out the same is true when measuring annual survival rates for waders/shorebirds.

Measures of annual survival rates can be hard to obtain because large-scale, long-term tracking of individuals is not easy and the resulting data contain many inherent biases. There are many different ways to estimate survival rates.

BlogKnotReturn rates: the proportion of marked individuals that are recaptured/resighted in subsequent years. Any bird that changes its location before the next resighting period will reduce the estimate of annual survival for the study population, even though it may still be alive.

Mark-recapture models: a range of different methods are available that allow the researcher to account for the effort that goes into looking for marked birds. Effectively this apportions the probability of missing a marked bird and the bird not being alive.

Dead recovery models: survival rate is inferred from the number of dead, ringed birds that are recovered. At its simplest, this does not take account of the number of birds ringed.

Complex modelling: used to separate apparent survival estimates into ‘true’ survival and site-fidelity, using live encounters and resighting/recovery rates. This helps to take account of the probability of birds leaving monitored sites.

Tracking studies: Survival estimates from radio-telemetry tracking studies are only available for a very limited number of shorebird species and for short periods. These measures were not included in this study.

BlogTTWash

Wouldn’t it be great if someone pulled together all of the available estimates of survival, produced by different methods? That’s what Verónica Méndez has done, with José Alves (University of Aveiro, Portugal), Jennifer Gill (University of East Anglia, UK) & Tómas Gunnarsson (University of Iceland) in Patterns and processes in shorebird survival rates: a global review, published in IBIS. (Click on the title to link to the paper).

In the paper, the authors  have reviewed published estimates of annual adult survival rates in shorebird species across the globe, and construct models to explore the phylogenetic, geographic, seasonal and sex-based variation in survival rates. The supplementary material includes an appendix detailing all of the available published estimates.

Key findings

Using models of 295 survival estimates from 56 species, Verónica and her colleagues showed that:

  • BlogGraphAs expected, survival rates for larger-bodied species are higher than for smaller species.
  • Survival rates calculated from return rates of marked individuals are significantly lower than estimates from mark-recapture models.
  • Annual survival tends to be slightly higher when estimated in wintering populations, but the difference from breeding season estimates was not significant.
  • As has been shown in many individual studies, female shorebirds often have lower survival rates than males, although this difference can be exaggerated if survival estimates are based on return rates and females are less site-faithful.
  • Survival rates vary across flyways, largely as a consequence of differences in the groups of shorebirds that have been studied and the analytical methods used.
  • BlogSpotSandPublished estimates from the Americas and from smaller shorebirds (Actitis, Calidris and Charadrius spp) tend to be underestimated.
  • By incorporating the analytical method used to generate each estimate within the models, the authors show that it is possible to ‘correct’ survival estimates, according to method used and genus, for a total of 52 species of 15 genera.

What about Slender-billed Curlew?

I asked Verónica whether it might be possible to estimate the annual survival rate for an adult Slender-billed Curlew. If there is a relict population somewhere then that’s a figure that’s going to be important to scientists who are trying to find them. Verónica said that these methods won’t provide a species-specific estimate but, given that the survival rate for the Numenius family is 0.71 ± 0.045 (standard error), the predicted survival should be somewhere within the range 0.62 to 0.79. If Slender-billed Curlews are no longer breeding successfully then half of any remaining adults will be disappearing every couple of years. That’s a sobering thought.

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Conservation Imperative

BlogTTDelawareA large number of the world’s shorebird populations are in decline and reduced annual survival rates seem to be a cause for concern in some parts of the world. Although it is impressive that the research team were able to find 295 survival estimates for this paper, I reckon that the data exist to calculate a whole lot more. Each of these extra results might not produce a novel paper but it would be great to see them published somewhere, as brief notes in the journal Wader Study for instance. That way, they will be available as bench-marks, next time researchers are worried about what appears to be a lowered level of annual survival. Meanwhile, here’s hoping that colour-ring readers will continue to provide sightings of birds for decades to come – there’s no substitute for long-term data-sets.

IBIS imageThis is an IBIS Open Access Review

Méndez, V., Alves, J. A., Gill, J. A. and Gunnarsson, T. G. (2018), Patterns and processes in shorebird survival rates: a global review. Ibis. doi:10.1111/ibi.12586

Verónica Mendez has written a blog about the methods used in her paper for the BOU blog series.


 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

 

Scottish Wader Woes

The latest report on Scotland’s terrestrial bird species, covering the period 1994-2016, does not make easy reading for wader lovers. All but one species is contributing negatively to the upland bird indicator, with declines of over 40% for breeding Lapwing, Curlew, Dotterel, Oystercatcher and Golden Plover. In this short blog, there are links to information that helps to explain what might be going wrong for Scotland’s waders.

The full report is available on the SNH website (https://www.nature.scot/information-library-data-and-research/official-statistics/official-statistics-terrestrial-breeding-birds)

One species has been increasing – Snipe up 22%

snipe abundance changeThe one spot of good news is that breeding Snipe numbers in Scotland have risen over the period 1994 to 2016. This is particularly encouraging, given declines in much of the rest of Britain and Ireland, as you can see in the map alongside and read in this WaderTales blog Snipe and Jack Snipe in the UK and Ireland.

In the map, produced for Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC), pink colours show abundance increases and grey areas show decreases.

Lapwing declines largest – down 63%

GHH pictureWhen a widespread species such as Lapwing is in decline this is bad news. Subtle difference in the way that lowland valleys are farmed may be part of the problem, as illustrated in this WaderTales blog based on work by Mike Bell, written up with the help of John Calladine, of BTO Scotland: 25 years of wader declines.

Curlew down 62%

Blog Jill PThe Curlew is causing huge concerns in Ireland and Wales, where conservationists are contemplating its disappearance as a breeding species. Scotland holds much larger numbers but a decline of nearly two-thirds suggests that there are major problems here as well.

Two WaderTales blogs tell the Curlew story. Is the Curlew really near-threatened explains why we should be so worried about what is happening and Curlews can’t wait for a treatment plan summarises a BTO-led paper from Sam Franks and colleagues which attempts to explain the patterns we are seeing in the species’ decline.

Dotterel down 60%

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Alistair Baxter

Most of the information about Scotland’s breeding birds comes from annual data collected by volunteers contributing to the Breeding Bird Survey (BBS), organised by the BTO, in partnership with JNCC and RSPB. Dotterel is different; here the counts are dependent on dedicated surveys of Scotland’s high-mountain plateaus. Concern for the species is very much linked to climate change but this blog, based on a paper by the RSPB’s Daniel Hayhow and colleagues, shows that there may well be other reasons for the species decline: UK Dotterel numbers have fallen by 57%. The figure for the decline may be slightly out-of-date but the blog isn’t.

TGG OycOystercatcher down 44%

In England, the latest BBS report shows an increase of 50% in Oystercatcher numbers but, in Scotland, where there are far more breeding pairs, the species is in decline. Oystercatchers: from shingle beaches to roof-tops looks at the history of the species’ spread from the shoreline, into the hills and onto roofs and considers the role of predation in recent declines.

Golden Plover down 43%

As noted in the press release about the new report ‘The golden plover population has declined by 43% since 1994 and stands at its lowest point since the BBS survey began. Declines may be linked to climate change, in part due to impacts on the abundance of craneflies during the breeding season’. There are two interesting papers about this by James Pearce-Higgins and colleagues.

golden ploverPearce-Higgins, J.W., Yalden, D.W. & Whittingham, M.J. 2005. Warmer springs advance the breeding phenology of golden plovers Pluvialis apricaria and their prey (Tipulidae). Oecologia 143: 470–476.

Pearce-Higgins, J.W., Dennis, P., Whittingham, M.J. & Yalden, D.W. 2010 Impacts of climate on prey abundance account for fluctuations in a population of a northern wader at the southern edge of its range. Global Change Biology 16: 12–23.

Common Sandpiper down 39%

The Breeding Bird Survey does not properly capture trends for species found mostly along rivers. Data for Common Sandpiper are derived from the BTO Waterways Bird Survey and the Waterways Breeding Bird Survey.

Why no Redshank?

Unfortunately, breeding Redshank are now patchily distributed across Scotland, with too few being picked up by BBS surveyors to make a contribution to Scottish population indices. Across the UK, the latest published BBS decline is 38%. UK graphs for Oystercatcher, Redshank and Curlew are shown below.

UK BBS


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

 

Well-travelled Ringed Plovers

Waders breeding in Chukotka, in the north-east corner of Russia, have a long way to travel at the end of the summer, in search of suitable habitats in which to spend the non-breeding season. A new study, using geolocators, shows that Ringed Plovers from this area fly between 8,900 and 12,100 km each autumn and in a very different direction to most other shorebirds that breed in the same area.

RP no geolocatorThis blog is based on a new paper in Wader Study, written by a team led by Pavel Tomkovich of the Moscow Zoological Museum. Their study describes the seasonal movements of tundrae Ringed Plovers from the easternmost edge of the subspecies’ distribution.

Pavel and his colleagues work in the south-eastern part of Chukotka, the region of Russia that is bounded by the Pacific Ocean to the east and the Arctic Ocean to the north. The data used in the paper were collected from five males that carried geolocators on their journeys to and from their wintering locations. Incredibly, during the mid-winter period, the birds were scattered from the Persian Gulf to the Nile Delta and south to Somalia, all of which are a very long way from Chukotka.

Range and distribution

RP snowy welcoms.jpg

Scene awaiting Ringed Plovers arrive in Chukotka in spring

Ringed Plovers breed over much of the Arctic region, from Greenland (and the eastern fringe of the northern Canadian islands), eastwards through northern Norway and right the way across Russia to the far eastern corner of Chukotka. The missing piece of the Arctic, between Newfoundland in eastern Canada and the western islands of Alaska, is the home of the very similar Semipalmated Plover. Additionally, there is a latitudinal spread in Ringed Plovers, with pairs in Europe breeding from Iceland throught to France.

Ringed Plovers breeding in the west

TTFReaders in Britain & Ireland will see Ringed Plovers in every month of the year. A colour-ringing study in Norfolk showed that many marked birds remained near their breeding sites for the whole year, while others migrated in a variety of directions in the autumn, exemplified by individuals flying south to France, north to Scotland and west to Ireland. In the spring, we see a strong passage of birds that have been wintering in countries in western Africa and southern Europe. They are on their way to breeding areas in Canada, Greenland and Iceland, in the west, and (to a lesser extent) Scandinavia in the north.

Ringed Plovers breeding in the north and east

Ringed Plovers breeding along the Arctic coastal fringe of Russia were believed to winter in eastern and southern Africa, right down to the southern tip of the continent. This new study, written up in Wader Study, the journal of the International Wader Study Group, is the first to reveal the migration routes of birds from the very far east of the range. The results are amazing, as illustrated by the map below which shows the movements of one male bird that wore a geolocator for a year. During that time he flew north-west to the Arctic coast of Siberia, south-west and south to Somalia, returning home through Siberia in the spring by a more southerly, inland route. His annual migrations totalled 25,000 km.

Global map

The migration route of one Ringed Plover. Map provided by Ron Porter

In the paper, the authors map and discuss the journeys of this Ringed Plover and four other males, in great detail. The ultimate winter destination of the birds that are not shown in this blog were the Nile Delta, the Persian Gulf (2) and the Red Sea. Unlike some other wader species, the migration strategy of Ringed Plovers is to use a wide range of suitable wetlands (often small and temporary) for only brief stops. It is unusual to see large flocks; the only important staging area to be identified so far, across the whole of Asia, is in north-central Kazakhstan.

Global perspective

global illustrationChukotka attracts birds from across the world. As well as Ringed Plover that fly here to breed from North Africa and the Arabian Peninsula, there are Knot from Australia and New Zealand, Semipalmated Sandpipers from South or Central America and Spoon-billed Sandpipers from anywhere from India to China – just to select three species that share the tundra with Ringed Plovers. The diagram alongside hints at the many different directions in which birds depart at the end of the breeding season. It’s really quite amazing!

RP three spcies

The Chukotka melting-pot: Knot from Australasia, Semipalmated Sandpiper from the Americas and Spoon-billed Sandpiper from Asia.

Historical perspective

Most Chukotka waders follow the East Asian-Australasian Flyway and it may seem surprising that Ringed Plovers are so different. The authors suggest that bird migration routes repeat the direction of expansion of a species’ historical breeding range, which will have changed markedly since the last Ice Age. In the late Pleistocene, Ringed Plovers may have had a largely Western Palaearctic breeding distribution with migration south to Africa each autumn. As the ice melted, and large areas of suitable habitat became available, the breeding distribution may have expanded eastwards, with these eastern breeders continuing to winter in Africa but travelling a lot further in autumn and spring.

Read the full paper here

RP geolocatorTranscontinental pathways and seasonal movements of an Asian migrant, the Common Ringed Plover Charadrius hiaticula tundrae. Pavel S. Tomkovich, Ron Porter, Egor Y. Loktionov & Evgeny E. Syroechkovskiy. Wader Study 124(3)

Further Reading in WaderTales

If you would like to learn more about migration to, from and through Britain & Ireland, have a look at Which wader, when and why?

RP lesser sandplover

Lesser Sandplover is one of the Chukotka species that migrates via the Yellow Sea

Geolocators are providing new and important information about migration but they need to be used safely. There’s a review here that will be of interest to anyone who is thinking of attaching devices to birds: Are there costs to wearing a geolocator?

There is a lot of concern about species such as Knot and Spoon-billed Sandpiper that breed in Chukotka and rely upon resources in The Yellow Sea. Read more in Wader declines in the shrinking Yellow Sea.

 

RP habitat


 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

 

 

Waders are long-lived birds!

The BTO longevity record for a wader is held by an Oystercatcher that was ringed as a chick by Adrian Blackburn in Lincolnshire (east coast of England) on 14 June 1970 and last caught by the Wash Wader Ringing Group on 16 July 2010, in virtually the same bit of the county. The time between ringing and last capture was 40 years 1 month and 2 days. Perhaps the bird is still alive?

Redshank

Will this Redshank live for another 10, 20 or 30 years?

Just to put records for British & Irish waders into context, the record for seabirds was set by a Manx Shearwater, at 50 years 11 months and 21 days, for waterfowl it’s a Pink-footed Goose (28 years 7 months and 7 days) and the longevity record for a passerine was set by a Rook (22 years 11 months 0 days).

This blog summarises records from the BTO Ringing Scheme between 1909 and 2016. These longevity records might be useful for a bird club quiz but they tell us very little about the health of wader populations. The real thing that is of interest is survival rates. Measuring the proportion of adult birds that survive through until the next year turns out to be exceptionally important to our understanding of wader conservation. There will be more about this later.

Records from the BTO scheme

Table2The list of records alongside is taken from the Online Ringing Report, produced by the British Trust for Ornithology. (The link to the longevity records can be found at the bottom of the web-page). The report covers all birds ringed and/or reported in Britain & Ireland up until the end of 2016. I aim to update this blog shortly after each new annual report is published.

For each species, longevity is defined as the time between ringing and the most recent report of that bird. For a chick, this figure is virtually equivalent to age but a bird first ringed when already an adult may be many years older than the longevity figure. The third column is the number of birds ringed for each species (up to the end of 2016). Records for species of which fewer than 3000 individuals have been ringed are given in italics, to indicate that the small sample size might be affecting the longevity record. With fewer birds being handled, the chance of catching a bird that is going to live a long time is low, as is the chance of it being caught again many years later.

In common with most groups of birds, the longest-lived ones are the biggest. Only Oystercatchers, Curlews and Bar-tailed Godwits have so far broken the 30-year barrier. At the other end of the scale, for smaller species, only the Ringed Plover has reached 20 years.

_DSC4194b

Grit wears even the hardest of metal rings (Richard Chandler)

With the passage of time, two things get older, the bird and its ring (or three things, if you think about the age of the ringers). Early rings were made of alloys of aluminium and these deteriorated quite rapidly, especially in salt water. Many of these rings will have given up long before the birds that were ringed. The widespread introduction of harder alloys in the 1970s has helped to increase longevity records.

Species such as Turnstone still wear out their rings and the oldest Oystercatchers are often birds that have carried two or more rings during the course of their lives. Such replacements only take place in areas where long-term studies are taking place, as was the case for the 40-year-old Oystercatcher mentioned above. It was first ringed as SS58540 but also known as FC15938 and FP99170.

FrenchAnother factor affecting our ability to appreciate just how long a wader can live is the use of colour-rings. The record-breaking Black-tailed Godwit is currently EF90838. This bird was hatched from an egg in Iceland in 1977 and received a metal ring on 24 October that autumn, at Butley in Suffolk. Many east-coast Black-tailed Godwits moult on the Wash (between Lincolnshire and Norfolk) and this bird was caught there in 1993. Already 16 years-old, it received two colour-rings that identified it as a bird taking part in a new Wash-based study, but not as an individual. In 1996, it was caught on the Wash again and given an individual set of rings. It was never caught again but was seen many, many times – most recently on 12 April 2001 by the late John Parslow.

Getting old

oldestThe annual renewal of a wader’s feathers enables an unringed individual wader to hide its age. The picture alongside was taken by Allison Kew, of the Wash Wader Ringing Group. This ringed Oystercatcher was well into its thirties at the time – older than any of the people in the photograph.

If still alive then a bird will migrate and attempt to breed in the same way as in the previous year, repeating the process for decades. Senescence probably kicks in eventually; there is some evidence of lower annual survival and reduced breeding success at the upper end of a species’ life-span. Long-term colour-ringing will enable this topic to be explored further in due course.

Survival

As mentioned earlier, although the longevity of a species might tell us something about annual survival rates, in that birds with high longevity almost certainly have the highest survival rates, being able to measure the proportion of adult birds that survive from one year through to the next is far more valuable.

Blog adultWaders adopt a ‘high-survival and low breeding-output’ strategy. Most waders have an annual survival rate of between 70% and 90%. This means that a pair of Lapwings, for instance, only needs to raise an average of 0.7 chicks per year to maintain a stable population. Unfortunately, this is not easy to achieve, as you can read here.

The occasional good breeding season can give a real boost to population levels, as we saw for Icelandic Black-tailed Godwits in the summer of 2017, as you can read here.

By collecting records of colour-ringed birds it is possible to measure the annual survival rates of wader populations, as explained here in this blog about Bar-tailed Godwits.

great knotWhen survival rates drop, the effect on population levels is immediate and dramatic, as discussed in this blog about the waders that use the Yellow Sea. Populations of Bar-tailed Godwit, Red Knot and Great Knot that winter in Australia and New Zealand were particularly badly affected by habitat removal, leading to a sudden drop in survival rates and rapid declines in numbers.

There is a global review of survival rates in this paper: Méndez, V., Alves, J. A., Gill, J. A. and Gunnarsson, T. G. (2018), Patterns and processes in shorebird survival rates: a global review. Ibis. doi:10.1111/ibi.12586. The paper is summarised in this WaderTales blog: Measuring shorebird survival.

Please help to measure survival rates

The chance of finding a ringed bird that breaks a current longevity record is tiny but every birdwatcher who reports a colour-ringed wader is helping to monitor survival rates. If you have ever done so – thank you.

 


 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

 

 

 

 

 

WaderTales blogs in 2017

19 WaderTales blogs were published in 2017, celebrating waders and wader research. Many of the articles are based on newly published papers, with the aim of making wader science available to a broader audience. Click on a link in bold to read an individual blog. 

Wader/Shorebird science and conservationringed-plover

Black-tailed GodwitsDSCN1827

b-dunlinIceland-based research

Blog adultBreeding Lapwings

Upland CurlewsRC single bird muddy edge

There are nearly 30 other WaderTales blogs. Here’s the full list. 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.


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.