Ireland’s wintering waders

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There’s still space for a few Knot

The island of Ireland is a great refuge for wintering waders, washed as it is by the warm waters of the Gulf Stream. It’s just a quick hop across the Atlantic from Iceland for Black-tailed Godwits, Golden Plovers, Redshanks and Oystercatchers. For birds travelling from Siberia, such as Bar-tailed Godwits and Grey Plovers, it’s a longer journey but one that’s well worth making.

If Ireland is such a great destination for shorebirds, why do the latest population estimates reveal a decline of nearly 20% in wader numbers in just five years?

This blog summarises the wader information, published in Estimates of waterbird numbers wintering in Ireland, 2011/12 – 2015/16 in Irish Birds. The totals in the report are split into counts for the Republic of Ireland and Northern Ireland but, given that waders don’t recognise borders, most of the comments in this blog relate to the whole of Ireland. The results for 2011-16 have been compared to the equivalent figures for 2006-11 and set in the context of the totals of wintering waders throughout the East Atlantic flyway, as combined by Wetlands International. The Irish data were collected by the amazing volunteers who make monthly, winter counts for I-WeBS (BirdWatch Ireland & National Parks & Wildlife Service) and WeBS (BTO/RSPB/JNCC in Northern Ireland).

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Headline figures

Fifteen species are considered in this report. The most numerous are Lapwing and Golden Plover, which account for an estimate over 170,000 individuals between them, whilst the smallest contributions are made by Purple Sandpiper (662) and Greenshank (1317). In total, the average estimated number of waders in the winters during the period 2011-16 is 429,170 birds but it should be noted that this total excludes two widespread and common species – Woodcock and Snipe – as well as the enigmatic Jack Snipe. To update previous estimates for these three species, which were last made using distribution and abundance data collected during Bird Atlas 2007-11 fieldwork, it would be necessary to run a special inland survey. There is also some question about Lapwing and Golden Plover numbers, simply because so many of these birds are found in areas that are not covered by monthly waterbird counts.

Biggest changes

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The Irish Sanderling population has increased by 13.2% in five years

The combined average winter maximum count of the 15 wader species examined in the report declined by 102,310 birds (19%) in the five-year period between 2006-11 and 2011-16. This is extremely worrying. If Lapwing and Golden Plover are excluded from consideration, as there is uncertainty about the completeness of counts, there are five species that are of particular concern; Knot numbers dropped by more than 40% and Oystercatcher, Dunlin, Redshank and Turnstone numbers by more than 20%. The Purple Sandpiper population estimate dropped by over 30% but relatively small numbers of this species are encountered around the rocky coast of Ireland. The only species to show increases were Sanderling, Bar-tailed Godwit, Black-tailed Godwit and Greenshank.

In a previous WaderTales blog, there is detailed information about population estimates for Great Britain: Do population estimates matter? In Great Britain there were similar rates of decline for Redshank and Turnstone (measured over an eight-year, rather than five-year period) but much smaller falls for Knot, Oystercatcher and Dunlin. The possible causes of the changes in Ireland are discussed in the paper in Irish Birds. They include flyway-scale declines (e.g. Knot and Curlew) and the possibility that more birds from the east are now wintering on the coasts of mainland Europe (e.g. Dunlin and Grey Plover).

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European context

Blog tableThe table alongside gives an indication of the relative importance of Ireland, Great Britain and, together, the British Isles to the birds that use the East Atlantic flyway during the winter period. The three columns show the percentage of each species found in each of the three regions. Summarised international counts, as used in the paper, were kindly provided by Wetlands International. In the case of four species, Ireland is host to a significant proportion of the Icelandic breeding population (Oystercatcher, Golden Plover, Black-tailed Godwit and Redshank).

Notes: As mentioned earlier, there are questions about the precision of estimates for Lapwing and Golden Plover, although the population trends are reliable. The Ringed Plover percentage seems high (98% for British Isles) but this may well reflect the fact that the Non-estuarine Waterbird Survey has uncovered significant numbers of the species on the open shores of Great Britain. These extra birds are included in the new totals for GB but not in the flyway total. The percentages for Black-tailed Godwit seem low, as discussed further down.

Ireland is particularly important for Golden Plover, Ringed Plover, Bar-tailed Godwit and Black-tailed Godwit, as well as for the Icelandic subspecies of Redshank. Greenshank is excluded because the percentages are below 1% of the flyway population for Ireland and for Great Britain.

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11% of Bar-tailed Godwit on the East Atlantic Flyway spend the winter in Ireland

Although there are important populations of breeding waders in Ireland, the shores and wet fields of the island really come into their own during July and August, when the first ‘winter’ waders arrive, and they only become quiet again in April and May, when the last birds head north and east to nest. A successful breeder is likely only to be away for four or five months, meaning that these waders will spend by far the largest part of the year in Ireland. The island is even more important for immature birds. Young Oystercatchers that arrive from Iceland, Scotland or perhaps Norway when just a few months old are likely to spend the next 30 months in Ireland before making their first trip north. There is a WaderTales migration blog about the Oystercatchers that fly from Iceland: Migratory decisions for Icelandic Oystercatchers.

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Curlew in the Republic

Curlew numbers in the Republic of Ireland illustrate the relative importance of the country for breeding and non-breeding populations. The winter population estimate for Curlew in the Republic is 28,300 but the most recent survey conducted by BirdWatch Ireland and NPWS, as summarised in the WaderTales blog Ireland’s Curlew Crisis, reveals that the number of breeding birds has crashed to just 138 pairs. Accounting for young Irish birds that have not started to breed, and even if we assume that all Irish birds stay in the country for the winter, then the total number of home-grown Curlew seen in non-breeding flocks is at most about 400. This means that every winter flock of 70 Curlew will contain an average of just one Irish bird. Far more deliver their curl-ew calls with a Scottish, Finnish or Swedish ‘accent’. The map below shows the migration pattern for Curlew ringed in or found in Britain & Ireland.

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Black-tailed Godwit

In the table above, it looks as if 18% of Iceland’s Black-tailed Godwits spend the winter in Ireland. This is probably an underestimate of the importance of the Republic of Ireland and Northern Ireland to the species. The flyway total for Black-tailed Godwit is given as between 98,000 and 134,000 in the Irish Birds paper and the percentage figure is based on 110,000. These three figures are almost certainly too high, as they build upon country-based estimates that have subsequently been revised. The true figure is likely to be around 60,000 to 65,000 (J. Gill pers. comm.), which would suggest that the maximum winter count in Ireland of 19,800 represents at least 30% of the islandica Black-tailed Godwits. Add in extra birds that moult in Ireland in the autumn, before moving further south to countries such as Portugal, and other birds that spend spring months on the island, and Ireland becomes even more important for Black-tailed Godwits!

blog BTMost birdwatchers might associate flocks of waders with estuaries but Black-tailed Godwit is an excellent example of a species that also relies on inland fields, either close to estuaries or along river valleys. Whilst undertaking PhD research on Black-tailed Godwits in south-east Ireland, Daniel Hayhow showed that there is insufficient time to find enough estuarine food during the mid-winter tidal cycles, with birds topping up their resources on grassland. You can read more about the energetic consequences of choosing to winter in eastern England, Portugal and Ireland in this blog: Overtaking on migration. Site designation and planning decisions need to take account of the grassland feeding requirements of Black-tailed Godwits and other waders that do not spend all of their time on estuaries, particularly Curlew.

Conservation implications

Some of the issues facing waders may be related to threats that species face in the breeding grounds. However, it may be easier to introduce measures that provide better protection and feeding opportunities in the wintering area, as ways of maintaining populations through the non-breeding season, than it is to deal with problems in the High Arctic. (Although we can all help by reducing carbon emissions, in order to minimise global warming, of course).

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Reading the report, I was reminded of the need to consider a range of conservation issues:

  • Care needs to be taken when considering shoreline developments. These can directly remove habitat or squeeze the width of the intertidal zone.
  • Increased harvesting of shellfish can affect species such as Oystercatcher and Knot and brings risks of introducing alien species and diseases.
  • In the drive to cut carbon emissions, tidal, wave and wind power developments need to be sited in appropriate places.
  • Off-shore harvesting of growing kelp beds has been suggested, as a way of producing fertiliser and biofuels. This process could reduce proetection for beaches and change the availability of resources for species such as Turnstone and Sanderling.
  • Grassland areas need to be considered (and not just estuaries) when planning protection for species such as Curlew and Black-tailed Godwit.

blog RKPaper

Estimates of waterbird numbers wintering in Ireland, 2011/12 – 2015/16. Brian Burke, Lesley J. Lewis, Niamh Fitzgerald, Teresa Frost, Graham Austin, and T. David Tierney. Irish Birds No. 41, 1-12.

There is a complementary paper in British Birds, covering Great Britain. The wader information is summarised in this blog: Do population estimates matter?


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

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Do population estimates matter?

blog top godwitsThis month (March 2019) saw the publication of Population estimates of wintering waterbirds in Great Britain, which includes all the wader species from Little Stint to Curlew. Given that the Wetland Bird Survey already covers about 2000 wetlands and provides annual monitoring, why do we need to know the total number of birds in Great Britain?

I suggest four reasons:

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

So, here’s the bottom line. In their 2019 review of waterbird numbers in British Birds, a team from BTO, WWT, JNCC & RSPB reveal that an estimated total of 4.9 million waders spend the winter in Great Britain. That’s about one third of all waders on the East Atlantic Flyway. Impressive!

Please note that Northern Ireland figures are included in an upcoming report for the island of Ireland.

Making the counts

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

blog CUFor species of wader that also make use of the open coast, the Non-estuarine Waterbirds Survey of 2015/16 (or NEWS III) provided additional data, updating the NEWS II figures from 2006/07. The vast majority of our wintering Purple Sandpipers are found on open beaches and rocky shores, as well as large numbers of Turnstone, Ringed Plover and Sanderling, together with significant numbers of Oystercatcher, Curlew and Redshank. There’s more about NEWS in this slightly dated blog: NEWS and Oystercatchers for Christmas.

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

The biggest losers

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

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

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

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

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

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

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

The biggest winners

There are four big winners in the period between APEP3 (2004-09) and the new review (2012-16), although, even here, not all as it seems.

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

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

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

There are other winners too, as you can read in the paper. At the start, I posed the question “how many Greenshank are there in the country during the winter?”.  The answer is 810, representing an increase of 200 since APEP3.

Game species

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

Golden Plover: The winter estimate remains as 400,000, as there has been no comprehensive, winter survey since 2006/7. Large numbers of Golden Plover arrive from Scandinavia, Europe and Iceland in the late summer, joining the British birds that choose not to migrate south or west. The GB breeding population is probably less than 50,000 pairs. Most breed in Scotland which has seen a breeding decline of 23% in the period 1995 to 2016 (BBS). Golden Plover is still ‘green listed’.

snipe-headerSnipe (Common): The winter estimate remains as 1,100,000 – a figure that was acknowledged in APEP3 as being less reliable than that of most species. At the same time, the GB breeding population was estimated as 76,000 pairs, indicating at least a 4:1 ratio of foreign to British birds, and that does not take account of the number of British birds that migrate south and west. Snipe are ‘amber listed’ but BBS suggests a recent increase of 26% (1995-2016). There is a WaderTales blog about  Snipe and Jack Snipe.

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

January counts

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

Looking forward

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

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

Paper

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

British Birds is a subscription journal. The issue containing this paper can be purchased separately. At some stage, the paper will become free-to-view.

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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

Ireland’s Curlew Crisis

To put the rapid loss of Ireland’s breeding Curlew into context, it’s equivalent to the human population of the Republic dropping from 4.8 million to less than 200,000.

blog muddy edgeIn their paper in Wader Study, the journal of the International Wader Study Group, Barry O’Donoghue and his colleagues reveal the results of the 2015-17 survey of breeding Curlew in the Republic of Ireland. The emerald isle used to be a haven for Curlew but there are now dire warnings that the species could be lost as a breeding species. Various estimates suggest that there were between 3,300 and 12,000 pairs in the 1980s but the current number may be as low as 138 pairs. That’s a fall of 96% in about thirty years.

The latest survey

Surveys in the summers of 2015, 2016 and 2017 focused upon areas that were known to hold breeding Curlew in the previous few years. Sites were identified, using data from Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC), the National Parks and Wildlife Service (NPWS) and BirdWatch Ireland, and then extended by 3 km to try to cover any satellite pairs. Additional records were sought from NPWS Rangers (who actively monitor wildlife in their patches across the country) and BirdWatch Ireland branches, supported by a public appeal, using traditional and social media. For details of the survey methods, please see the paper ( link below).

Doing the sums

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Loss of habitat is a major issue for Ireland’s Curlew – blocks of forestry and fragmentation.

Volunteers and staff, who surveyed previously-occupied areas, discovered 128 breeding pairs during the summers of 2015-17. Nationwide publicity added an additional ten pairs, making a minimum count of 138 pairs of breeding Curlew in the whole of the Republic of Ireland. When comparing this figure to historical estimates of national populations, the authors use the conservative figure of 3300 pairs, which is at the lower end of the smallest estimate. This suggests a drop of 96%. If the highest previous estimate of 12,000 pairs had been used, we would be talking about a decline of 99%.

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Curlew chicks are a rare sight – productivity is very low in Ireland

Curlew were recorded at densities of approximately three pairs per 1,000 ha of suitable habitat (0.3 pairs per km2). This suggests that, in these occupied areas of raised bog, wet grassland, wet heath and upland blanket bog, Curlew are living in similar densities to those of the 1980s. They are just found in a much reduced total area.

One positive finding is that 56% of the surveyed Curlew population occurs in protected sites, whether Special Protection Areas (SPAs) or Special Areas of Conservation (SACs) designated under European legislation, and/or Natural Heritage Areas (NHAs) designated under national legislation.

Caveats

The focus of the 2015-17 survey was upon sites that were known to hold Curlew during the period between 2007 and 2014. In an ideal world, there would have been surveys of randomly selected areas in other parts of the country, to establish the number of birds that might have been missed. This would have been an expensive exercise and the consequences are probably not particularly significant because:

  • blog mapDuring the breeding seasons of 2008 to 2011, the whole of Ireland was covered for the Bird Atlas.  The map alongside shows the breeding distribution from this joint BTO, Birdwatch Ireland and SOC project. It shows that there are many areas that no longer have breeding Curlew (black triangles).
  • Curlew are highly site-faithful. Birds are long-lived and unlikely to move between years, so any site occupied in 2011, for instance, would be expected still to hold some of the same birds four years later.
  • Curlew return to breed close to areas where they were raised. The 3-km buffer zone is likely to have picked up young birds setting up their own territories, although precious few chicks fledge successfully these days, anyway.
  • The Curlew is a much-loved bird. A major publicity campaign led to the discovery of only 10 pairs outside the main study areas. If a further 30 pairs were missed (which seems high, representing only a 25% success rate in the call for additional records) then this would only change the ‘96% decline’ headline to a ‘95% decline’.

blog numeniiniWhat has gone wrong?

This blog focuses on the results of the 2015-17 Irish Curlew  survey. Previous WaderTales blogs provide information that sets these declines in context and discuss the problems being faced by the species.

There is a global crisis for large waders as you can read in this review: Why are we losing our large waders?

Each autumn, Irish Curlew are joined by thousands of migrants, largely from Finland, Sweden and Britain. There are still large flocks of Curlew in winter, so it may be hard to persuade people that the Curlew is in trouble. Here are the arguments: Is the Curlew really near-threatened?

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The key issue for breeding birds is habitat loss, as discussed in Mary Colwell’s excellent book Curlew Moon, reviewed here: Curlew Moon.

A review of the associations between Curlew and their habitats suggest that conservation action needs to focus on habitat restoration and reducing the impacts of predators (the latter, at least in the recovery phase): Curlews can’t wait for a treatment plan.

The way that land is grazed has a major impact on breeding Curlew: Sheep numbers and Welsh Curlew.

Acknowledgements and action

blog logoThe 2015-17 survey in Ireland was commissioned by the National Parks and Wildlife Service. Confirmation of the severity of the decline led to the establishment of a Curlew Task Force in January 2017 and a Curlew Conservation Programme, aimed at increasing the productivity of remaining Curlew pairs. CCP logo adapted from original artwork by Anne Harrington Rees.

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Fencing and habitat creation

This study has identified strongholds for breeding Curlew in the Irish Republic and conservation action is currently being implemented in Donegal, Kerry, Kildare, Galway, Leitrim, Mayo, Monaghan and Roscommon. For information on what is an innovative approach to tackling the Curlew crisis, read more about the National Parks and Wildlife Service’s Curlew Conservation Programme here.

Paper

The full paper is in the journal Wader Study. Click on the title below for a link:

O’Donoghue, B., A. Donaghy & S.B.A. Kelly. 2019. National survey of breeding Eurasian Curlew Numenius arquata in the Republic of Ireland, 2015–2017.

Wader Study 126(1): doi:10.18194/ws.00130

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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

The waders of Northern Ireland

blog CU postNorthern Ireland is a great place for wintering waders but the same can no longer be said for its breeding species. There are far too few places left in which Curlew bubble and Snipe drum.

Waders provide some of the best birdwatching spectacles in Northern Ireland, as flocks swirl around coastal estuaries, when the tide rises on a winter’s day. Birds fly in from as far away as Canada and Russia but there are particularly strong links to Iceland, about which there will be more later. Every year, winter counts by volunteers, who help with the Wetland Bird Survey, alert us to the ups and down in wintering populations on loughs and estuaries. Unfortunately, we know much less about breeding species such as Lapwing, Redshank, Snipe and Curlew – four species that feature in a new Northern Ireland survey in the summer of 2019. Although the annual Breeding Bird Survey monitors birds such as Song Thrush and Willow Warbler, waders are just too thinly spread in Northern Ireland for it to be possible to pick up any year-to-year changes. That’s why they need a special survey.

blog L flightWe know that there were some great wader hot-spots in the years 1985 to 1987, when a major Northern Ireland survey took place, and that large drops in numbers were reported in 1999 and again in 2013, after other dedicated surveys, but what is happening now? Are there still places where Snipe drum and Curlew bubble? The BTO in Northern Ireland is asking local and visiting birdwatchers to revisit some of the best places that were identified in previous surveys, to look for breeding waders and to assess the habitats that remain. This work complements work being undertaken by RSPB Northern Ireland. If you think that you may be able to help click here to find more information.

Not looking good?

Although it would be nice to be proved wrong, the expectation is that breeding wader numbers will have declined still further. This means, of course, that any remaining sites that still hold species such as Redshank and Lapwing, are going to be even more important than they were thirty years ago. Pessimism is based on trends elsewhere; numbers of breeding waders are falling throughout the UK and increased agricultural intensification within the Republic of Ireland has caused sharp declines in the focal species of this survey – Lapwing, Redshank, Snipe and Curlew. The following notes give some highlights about Northern Ireland’s waders and point out some of the things that we don’t know (yet).

Lapwing

blog Lap mapThe Lapwing has quietly disappeared from much of Northern Ireland over the last fifty years. The black triangles in the map alongside represent 10-km squares that lost their breeding Lapwings between the two atlases of 1968-72 and 2008-11. Previous Northern Ireland surveys of breeding waders in 1985-87 and 2013 suggest that the number of pairs dropped from an estimated total of 5250 to a total of 860 – that’s a loss of 5 out of 6 pairs. The new survey this summer will update breeding numbers in the species’ heartland areas, as long as sufficient volunteers step forward to help with coverage. (Here’s a link to the results of the 2013 Northern Ireland wader survey.)

Redshank

blog RKThere is no recent estimate for the number of breeding Redshank in Northern Ireland. Across the UK, the Breeding Bird Survey suggests that we have lost 41% of breeding birds since 1995, and the decline was well underway by then. The survey this year provides a good opportunity to learn as much as possible about this threatened species.

In the late summer, the tiny Northern Ireland population is joined by Redshank from Iceland and Scotland. There are also small a number of movements linking Northern Ireland with Wales and England; some of these might be of birds from further east in Europe that were ringed in Britain. Strangford Lough peak counts of over 2000 in October illustrate just how much of an influx there is each autumn.

Snipe

blog SN mapThe lowland wader survey in 1985-87 suggested that the Northern Ireland population of Snipe was about 5725 pairs. By the time of the next survey in 1999, that number had dropped to 3993 and then to 1123 in 2013. That’s a drop of 80%. Snipe seem very sensitive to habitat change, especially drainage. The map alongside shows the change in abundance between 1988-91 and 2008-11 across Britain & Ireland. There is an interesting mix of losses (grey) and increases (orange) in Northern Ireland. It will be great if the 2019 survey picks up some new Snipe hot-spots. One of the key elements of the fieldwork this year is to record habitat data and field-use. What habitats do Snipe still breed in and can these be expanded and replicated elsewhere within Northern Ireland?

blog SN groundThere’s a WaderTales blog about Snipe & Jack SnipeMany of the birds that are seen in Northern Ireland in the winter have flown across the Atlantic to escape the snow and cold of Iceland but there are also large numbers from Scandinavia and continental Europe

Curlew

The Curlew is in huge trouble across the whole island of Ireland. Surveys of random squares in 1985-87, 1999 and 2013 suggest that the number of breeding pairs in Northern Ireland dropped from 5000 to about 500 over the period. There is talk about potential extinction as a breeding species in Ireland and Wales. This may seem ridiculous when you can see flocks totalling 2000 birds around Lough Foyle, on a winter’s day. However, these are almost exclusively migrants, from Finland, Scandinavia and Scotland. One of the hopes is that the new survey will pinpoint new hot-spots for Curlew. There is already concerted action to try to bolster numbers through the Lough Erne Landscape Partnership.

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Other Northern Ireland waders

Oystercatcher: Many wintering Oystercatchers leave Northern Ireland in the spring, heading for Iceland, Scotland or perhaps Norway (more in this wader migration blog). By that time, resident adults will already have moved inland or onto beaches to breed and other birds will have returned from southern wintering areas.

blog RPFlocks of young birds are found on estuaries in the summer, as Oystercatchers typically don’t breed until three years old. We know that the number of breeding Oystercatchers in Scotland dropped by 38% between 1994 and 2017 but English numbers rose by 49% (read more here). We don’t know what’s happening in Northern Ireland.

Turnstone: Wintering birds are mostly thought to come from Greenland and Canada but a December capture of a bird from Sweden suggests that there might be a link to the east as well.

Ringed Plover: The new survey in Northern Ireland is not designed to monitor beach-nesting Ringed Plover. The most recent UK-wide survey of the species was in 2007, when the Northern Ireland population estimate was 147 pairs, similar to the estimate at the time of the previous survey, in 1987. In the same period, numbers dropped in Scotland (-42%) and England (-29%). Link to summary of paper.

blog GP mapGolden Plover: Ireland is a winter destination of choice for many Golden Plover that breed in Iceland. The recovery of a Belgian-ringed bird in 2006 suggests that some birds may arrive from the east as well. Wintering numbers are half what they were 25 years ago, according to WeBS data for Northern Ireland. A few breeding birds can still be found in the western parts of Northern Ireland but they have been lost from most other areas.

Grey Plover: It’s a long way from Siberia to Northern Ireland, so perhaps it is not surprising that not many Grey Plover make it this far west!

Knot: The best place to see Knot is in Strangford Lough, where numbers peak at over 4000 in some winters. The only two foreign-ringed birds were shot wearing Icelandic rings in 1957 and 1975 (when shooting them was legal). Northern Ireland’s wintering Knot probably breed in Greenland or Canada and migrate via Iceland.

Sanderling: The Sanderling that are seen around the coast in winter months, in small numbers, will almost certainly breed in Greenland. Numbers are higher in spring, when birds from further south stop off on their way to Iceland and then Greenland.

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Dunlin: This year’s survey of Lapwing, Redshank, Snipe and Curlew should really include Dunlin, as they share similar breeding habitat. However, it will be a very lucky volunteer who finds a displaying adult. Birds of the schinzii (green arrows) and arctica (yellow) race pass through in spring and autumn but the wintering birds are of the alpina race (orange).

blog WK mapWoodcock: The black triangles in the map opposite show the parts of Northern Ireland that have lost breeding Woodcock in the last 50 years. Data are from Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC). In late autumn, birds fly in from counties such as Germany, Norway and Russia. See this blog.

Black-tailed Godwit: All is not gloom and doom in the world of waders; there are six times as many Black-tailed Godwits wintering in Northern Ireland as there were 30 years ago. Great views of these Icelandic visitors are provided at the RSPB reserve at Belfast’s Window on Wildlife. This blog explains why numbers have taken off in recent years.

Bar-tailed Godwit: The Bar-tailed Godwit that are seen in Strangford Lough and elsewhere are birds from northern Norway and Russia. There seems to have been little change in numbers, according to Northern Ireland WeBS counters.

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Whimbrel: A few Whimbrel drop in during autumn passage but far more appear in spring. Most Icelandic Whimbrel can fly straight to West Africa in the autumn but 80% stop off on the way north, many in Northern Ireland (see graphic above). You can read more here.

From Avocet to Pectoral Sandpiper

There is a supporting cast of waders that visit Northern Ireland. This blog provides more information on wader migration: Which wader, when and why?

A call for help

blog habitatAs must be obvious by now, BTO Northern Ireland is looking for volunteers to help with wader surveys in 2019. Sites are discrete lowland wet grassland areas, small enough to survey in one morning. At least two or ideally three visits to each site are required between mid-April and mid-June, with at least two weeks between each visit.

Each field or sub-unit needs to be covered on foot and the number of Lapwing, Curlew, Redshank and Snipe are counted per field. Some additional habitat recording is required, e.g. recording grazing, rush cover and estimating dampness.

blog mapSites are located in five broad areas (see map):

  • Loughs Neagh and Beg
  • Blackwater Catchment
  • Tyrone Fairy Water Bogs
  • Upper Lough Erne
  • Lower Lough Erne (these sites will be covered by the RSPB)

More details are available here, on the BTO Northern Ireland website. There will be a free training session on 29 March. Contact shane.wolsey@bto.org if you have any questions or would like to volunteer.

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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.

 

From local warming to range expansion

blog adultOver the last century, Icelandic black-tailed godwits have increased 10-fold in numbers and their breeding range has expanded throughout lowland Iceland. Although changing climatic conditions seem likely to have enabled this process, how might warmer conditions have led to this growth? This blog is a summary of a paper by José Alves and colleagues in Ecology & Evolution.

Setting the scene

If scientists are going to try to predict species’ responses to future climatic conditions, they will need to understand the ecological, behavioural and historical factors that influence how change happens. In other words, what mechanisms can link changes in climate with changes in population size and distribution?

tableAppreciating how local climate effects can potentially scale up to population-level changes requires climate effects to be measured across a population. Iceland is a great place to study these processes as it has been getting warmer since at least 1845, as measured by one of the longest temperature time-series in the world. The country hosts internationally-important breeding populations of many migratory bird species, for which changing climatic conditions could have important implications, including Black-tailed Godwit. The data in the table alongside have been extracted from a report to AEWA that was discussed at the 12th Standing Committee in Jan/Feb 2017.

A booming population

godwit spread

Expanding breeding range in Iceland

In the early 1900s, Black-tailed Godwits were restricted to the southern lowlands of Iceland but, since then, birds have gradually colonised coastal lowland areas throughout the country, with larger areas closer to occupied sites being colonised first (as described in this WaderTales blog). The population now numbers over 50,000 individuals, which is likely to represent an approximately 10-fold increase over the last century.

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Newly hatched chicks, still in their nest-cup, well hidden in grass

Icelandic godwits are long-lived migratory shorebirds with a typical lifespan of between 15 and 20 years. They nest in lowland wetlands dominated by grasses or by dwarf birch and sedges. They hide their nests, which means that they require sufficiently tall vegetation to conceal the nest and an incubating adult. Both vegetation growth and the timing of emergence of invertebrate prey for wader chicks are strongly temperature-dependent, particularly at high latitudes, which means that the timing of nesting and the growth-rate of chicks are likely to be influenced by local temperatures.

blog colonisationOver eight years, during which temperatures in Iceland varied substantially, José Alves and colleagues were able to quantify the influence of temperature on laying dates and the duration of the pre-fledging period of Icelandic godwits, and the subsequent influence of hatching dates on recruitment of chicks to the wintering or subsequent breeding population. The authors then used these relationships to model how the timing of breeding and the annual recruitment of juveniles into the breeding population may have contributed to population growth and the successful colonisation of new (and now warmer) parts of Iceland.

Catch your godwits

blog cr chickBlack-tailed Godwits are very good at hiding their nests and chicks! These three quotes from the paper help us to appreciate the effort that goes into establishing some of the key facts that underpin the modelling at the heart of this paper:

  • “Every nest was visited regularly and successful nests were revisited at the estimated hatching date, in order to capture and mark chicks and adults with individual combinations of colour-rings.”
  • “For each family, one of the adults was captured using either a nest-trap or a hand-held net-gun.”
  • “In 2012 and 2013, 32 godwit families were tracked during chick rearing, from hatching to fledging (n = 18) or brood loss (n = 14).”

Away from the main study area, volunteer ringers, led by Pete Potts of Farlington Ringing Group, caught, measured and colour-ringed chicks, thereby providing an assessment of hatching dates of chicks in other parts of Iceland.

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The assessment of which chicks subsequently survived and recruited into the adult population relied heavily upon the observations of hundreds of birdwatchers, throughout Western Europe, who take the time and trouble to report sightings of colour-ringed birds. Examples of their dedication and links to other papers that rely upon their efforts can be found in Godwits and Godwiteers.

Major Findings

Effect of temperature on timing of breeding season events: In Icelandic godwits, mean laying dates were approximately 11 days earlier in the warmest of years than in the coldest (two-degrees Celsius lower). This earlier start to the breeding season is thought to be linked to faster vegetation growth in warmer springs. The lengths of the chick pre-fledging period varied by only about 3.6 days between the warmest and coldest years but this additional difference means that fledging can happen a fortnight earlier in the warmest of years. 

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blog juv flocksProbability of recruitment: Early-hatched chicks are more likely to survive and recruit into the adult population, and the 11-day advance in hatch dates in warm years equates to an increase in absolute recruitment probability of about 10%. The additional benefits of more rapid chick growth and fledging in warmer years probably further increases this differential. In cold years, when most nests are laid late, very few chicks are likely to recruit to the adult population. For example, in 2011, the coldest year recorded during the study, only about 16% of 118 ringed chicks recruited into the wintering population. Early-fledged chicks presumably have more time to improve body condition prior to migration, there is an increased probability of travelling in adult-dominated migratory flocks (see graphic from Gunnarsson 2006), and earlier departure for wintering areas may allow more time in which to find a favourable wintering location.

blog big chickRegional variation: Traditional breeding sites are warmer, and so nests are likely to be earlier and incubation shorter, which means that more of the chicks from these areas are likely to survive and recruit into the population. The range expansion in this system could therefore have been driven by increased productivity and dispersal from traditionally colonised areas, supplemented by increased productivity within newly colonised – and now warmer – areas. Given the high levels of natal philopatry in Black-tailed Godwits (WaderTales blog about philopatry), the authors suggest that improved breeding conditions, following colonisation of new areas, have fuelled local population increases and further range expansion.

Are these findings applicable to other species?

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Sightings of colour-ringed juveniles, such as this one in eastern England, helped to establish recruitment rates.

The authors of this paper have been studying a species breeding at the northern limit of its range, in a country that has been subject to rapid climate change and in which there are relatively large differences in temperatures over quite small distances. This provides an ideal gradient over which to study change. Also, and unusually, it was possible to measure recruitment of chicks from right across Iceland, because of the colour-ring reports from observers. This set of circumstances have combined to enable the team to show that warming trends have the potential to fuel substantial increases in recruitment throughout Iceland, and thus to have contributed to local population growth and expansion across the breeding range. They propose that the same factors may be harder to tease apart for other species, in different environments, but that advances in lay dates and increased recruitment associated with early hatching may be key processes that drive population and range changes in migratory systems.

Paper

Linking warming effects on phenology, demography and range expansion in a migratory bird population. José A. Alves, Tómas G. Gunnarsson, William J. Sutherland, Peter M. Potts & Jennifer A. Gill.

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Juveniles gather together in the late summer, prior to departure


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.

 

In search of Steppe Whimbrel

blog in flightIt’s unsurprising if you have not heard of a Steppe Whimbrel; the subspecies was declared extinct in 1994. In this context, a new paper in Wader Study, based on detailed studies of two birds that were found in Mozambique in 2016, adds immensely to our knowledge.

Bleak times for the Numeniini

The curlew family is facing huge pressures across the globe. Eskimo Curlew and Slender-billed Curlew are either extinct or close to extinction, with no confirmed sightings for 56 and 18 years, respectively. We are definitely losing species but are we losing diversity within individual species too – as suggested by the rarity of the Steppe Whimbrel and the fragmenting distribution of the Hudsonian Godwit? There is a lot of information about the current status of different populations and subspecies of the Numeniini  family in Why are we losing our large waders? a WaderTales blog about curlews, godwits and the Upland Sandpiper based on a review paper by James Pierce-Higgins and colleagues.

As a species, the Whimbrel is categorised as ‘of least concern’ but the ‘once extinct’ Steppe Whimbrel would be considered as ‘critically endangered’ if it were to be a species, rather than a subspecies.

Whimbrel are circumpolar in distribution and it is generally accepted that there are four subspecies:

  • phaeopus breed from Iceland through Scandinavia and into western Siberia; they spend the non-breeding season largely in western and southern Africa.
  • variegatus breed across the rest of north-eastern Russia and migrate to southeast Asia and Australia.
  • hudsonicus breed across northern Canada and Alaska and migrate to Latin America.
  • alboaxillaris are thought only to breed in the steppes of Russia and Kazakhstan, at the centre of the European land-mass, and to winter only in southeast Africa.

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First find (and identify) a Steppe Whimbrel

The fact that Steppe Whimbrel was considered to be extinct just 25 years ago gives a clue as to how hard it is to find one. Details about recent records are summarised in a new paper in Wader Study by Gary Allport and colleagues, that forms the basis of this WaderTales blog. Three breeding sites have been identified, holding a maximum of 19 breeding pairs, in total, and a maximum autumn count of 11 birds has been recorded on passage, on the shores of the Caspian Sea in 2010. The two birds that Gary found in Maputo, Mozambique in February 2016 are the first wintering records in Africa (or anywhere else) since 1965.

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The photographs above show that the two birds found at Maputo by Gary Allport of BirdLife International are different in several respects to the phaeopus with which they associated:blog on ground

  • Steppe Whimbrel are bigger
  • There are cleaner/paler in overall appearance
  • The rump is paler
  • They have white axillaries

For more information see Allport, G. & C. Cohen. 2016. Finding Steppe Whimbrel: discovery and identification in southern Africa. AfricanBirdlife 4: 48–54. If you come across what you think is a Steppe Whimbrel, possibly in eastern Africa during the non-breeding season, check for white under-wings and take as many pictures as possible!

blog in handAt the time of the discovery of the two Steppe Whimbrels, BirdLife had already got a strategy in place to deal with the unexpected appearance of a Slender-billed Curlew – ever hopeful that this species is not extinct. If seen in the non-breeding season, a bird was to be caught and satellite-tagged, in order to try to find its breeding area. The same procedures seemed appropriate for the Maputo Steppe Whimbrels and one bird was duly caught and tagged. That’s probably another story – anticipation – tension – concern for the bird’s safety – relief when it accepted its tag and behaved normally – and elation when data started coming in.

Local movements

blog photographerThe Maputo area, in which the two Steppe Whimbrel were found, comprises about 6 km of tidal muddy sand banks and flats. The area is heavily used by people, with zoned sections for various uses including traditional worship and tourism. The two Steppe Whimbrel were found by chance in February 2016, at the high tide roost on the upper beach. One was bigger than the other, suggesting a female and male. No other alboaxillaris were found in a larger population of 650 Whimbrel photo-identified in Maputo Bay. This paper talks about the discovery: Allport, G. 2017. Steppe Whimbrels Numenius phaeopus alboaxillaris at Maputo, Mozambique, in February–March 2016, with a review of the status of the taxon. Bulletin African Bird Club 24: 27–37.

The local movements of the two Steppe Whimbrel in Maputo Bay, Mozambique, were studied opportunistically from February to March 2016. Both birds were found to be part of a local sub-population of ca. 30 Whimbrel which held individual feeding territories on sandy shorelines. There are important details about behaviour and habitat-use in the Wader Study paper. The male was seen more frequently and predictably.  Knowledge of his movements made it possible to catch him, by dazzle-netting at night, on 6 March. Metal and colour-rings were added, together with a PTT satellite tag. A DNA sample proved that he was indeed a male.

The male was noticeably plump when caught, suggesting that he was already preparing for northward migration. Data gathered from the tag during the period before departure added valuable extra information about key feeding areas north of the main study area, where mangroves make it hard to observe birds.

Time to fly north

blog mapThe female Steppe Whimbrel was last seen in the Maputo area on 28 February 2016, and it is suggested that she may have left the areas on or shortly after this date. The last sighting of the male was on 24 March 2016 and, using information from his PTT satellite tag, the Mozambique team know that he started to migrate the next day. Although nearly a month after the possible departure of the female, this is still one month earlier than the onset of migration for the phaeopus subspecies. This is not unexpected; phaeopus birds are heading for higher latitudes than alboaxillaris, which breed in the heart of the Eurasian continent, in the steppes of Asia.

Upon leaving Mozambique, the tagged male headed over Tanzania before the scheduled transmission phase ended. At the start of the next recording period, the bird had travelled to the northern end of the Great Rift Valley in Ethiopia. He then turned in a more easterly route to the Somali coast. During the tag’s next ‘off phase’ he crossed the Gulf of Aden where he was picked up moving up and down the coast before settling on some salt-pans in the area of Little Aden.

The tagged bird made a 4,659-km journey in six days to Aden, Yemen and his migration route was consistent with the direction of travel for the known breeding areas of alboaxillaris. The track data are the first firm evidence of a long-suspected African transcontinental migration route for southeastern Afro-Palaearctic coastal waders.

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The tag was attached to the back of the Steppe Whimbrel. Feathers have been parted to show the  tag. After two months, the tag dropped off.

The tagged Steppe Whimbrel stayed in the Little Aden coastal area of Yemen until 10 May, when the pattern of fixes changed to a stationary location in the northwest side of the bay. This suggested that the tag had fallen off the bird, possibly floated across the bay on the prevailing southeast wind and then settled on the shoreline. Confirmation of the loss of the tag came on 14 August, when Gary Allport came across the same Steppe Whimbrel, wearing colour rings, back in Maputo. That must have been a great moment.

Key take-home messages

tweet 4If you are on the African shores of the Indian Ocean, in Africa’s Great Rift Valley or perhaps the coasts of western India or the Middle East, please check out any Whimbrel you see. Steppe Whimbrels live up to their names – look out for the white (albo) underwing (axillaris). Perhaps you will find the next Steppe Whimbrel and it will be in a location where capture is again possible. Maybe your bird will carry the next PTT transmitter for long enough to tell conservationists where to look for what must be a tiny population of breeding Steppe Whimbrel. Peter Ryan of the Percy Fitzpatrick Institute of African Ornithology (University of Cape Town), has recently secured funding from the Mohamed Bin Zayed Fund to tag Steppe Whimbrel. He and Gary are on the look-out for any birds that might be suitable for further study. 

blog in hand underwingOne of the great things about this tracking study is that it acts as a trial-run, should anyone find a Slender-billed Curlew or (even more unlikely) an Eskimo Curlew. We know that BirdLife scientists and their colleagues have the skills needed safely  to catch a rare, large wader and to maximise the amount of information that can be gathered about its migratory movements. Fingers crossed that it’s not too late to find out what is happening to other Steppe Whimbrel, or possibly even Slender-billed Curlew. Sadly, I think that we have to admit that the Eskimo Curlew is now almost certainly extinct.

Paper

Click on the paper details below to link to the Wader Study website. Full text is only available to members of the International Wader Study Group.

Allport, G.A., P.W. Atkinson, M. Carvalho, N.A. Clark & R.E. Green. Local site use and first northbound migration track of non-breeding Steppe Whimbrel Numenius phaeopus alboaxillaris (Lowe 1921). Wader Study 125(3). doi:10.18194/ws.00126

 

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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.

 

 

 

Winter territories of Green Sandpipers

Winter is a very different prospect for a Green Sandpiper that spends the non-breeding season in England, rather than Spain, Portugal or countries in northern Africa. Are British winterers living life ‘on the edge’ and how do they cope? One way is to defend resources within clearly-defined territories.

Life in Hertfordshire

blog2 preenKen Smith, Mike Reed and Barry Trevis have been studying a colour-ringed population of Green Sandpipers in Hertfordshire (an English county just north of London) since 1983. The focal point of their activities is Lemsford Spring, a Hertfordshire & Middlesex Wildlife Trust nature reserve. The site is  a set of disused watercress beds that provide plenty of freshwater shrimp (Gammarus pulex) in shallow lagoons fed by freshwater springs. Over the years they have been able to use their colour-ringed birds to study return rates from year to year, behaviour and local habitat use. Using radio-tags they have looked at nocturnal activity patterns and more recently they have been using GPS geolocators to find where their birds go to breed.

blog2 movementsThe highest numbers of Green Sandpipers in southern England occur in late summer, when many passage birds pass through the country, but a few birds stay for the whole winter. The Lemsford studies show that colour-ringed birds have a high return rate from one winter to the next. These birds are actually in the general area of Lemsford for most of the year, only leaving to breed for two or three months. Upon return, in late summer, they use other local sites such as gravel pits, only switching to the watercress beds in the autumn.

Individuals birds visit a suite of sites; by tracking birds wearing radio tags, the team were able to establish that even birds that fed at Lemsford Springs (below) during the daytime would roost communally at the local gravel pits overnight.

blog2 springs

Effects of cold weather

The research team found that the patterns of behaviour of the Hertfordshire Green Sandpipers varied with local weather conditions. During extremely cold weather in January and February the birds switched to roosting overnight at the watercress beds, where they could also feed. In these conditions, with the water frozen at gravel pits, roost sites were accessible to predators. Automated monitoring of tag locations showed that birds were active for around 80% of each daytime period at all times of year. Nocturnal activity varied from around 16% in autumn to over 40% in cold conditions in midwinter. This suggests that a low level of night time activity is normal in Green Sandpipers and that higher levels, found during extremely cold winter conditions, are the result of birds attempting to increase their daily food intake.

Annual survival

The return-rate of colour-ringed birds can be used as a surrogate for survival rates, bearing in mind that any bird that changes its wintering area will reduce the apparent survival rate, although still alive. (See WaderTales blog on measuring survival rates based on review paper in IBIS)

blog2 gravelOnce established in the Hertfordshire area, individual Green Sandpipers were likely to turn up in subsequent  winters, with little difference in return-rates between young birds, ringed in their first winter, and adults. There was considerable variation from year to year, with the return rates varying from 68.7 to 100%; the lowest being between 1986/87 and 1987/88, when another local winter site (Cole Green) became unsuitable. Birds using that site presumably went elsewhere or died. The average apparent annual survival rate was 83.5% (or 84.7% if account is taken of the disappearance of Cole Green). In the only other similar study, in northern Germany, the mean return rate was only 56%, with few birds returning in the year after a severe winter. In the Hertfordshire study, there is a correlation between the overall return rate of colour ringed birds from one winter to the next and the number of nights with air frost in the first winter (r = -0.86, n = 7, P < 0.05). These results suggest that birds suffer increased mortality in severe winters.

Territoriality

One of the interesting things that became apparent, once individuals could be identified using colour-rings, was that some of the Hertfordshire Green Sandpiper were highly territorial, with similar patterns of behaviour each year.

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When Green Sandpipers appear in late summer they are usually found in small flocks, which include the colour-ringed full-grown adults and young birds of the year. At some point in the autumn, possibly triggered by low temperature or shortening day-length, the behaviour suddenly changes, with some of the birds establishing defended territories on the lagoons, from which they chase all interlopers. This initial burst of territoriality has been captured in the excellent images above and below this paragraph. Once the territories are established they are maintained by subtle calling displays, with only occasional full-on disputes.

blog2 fight 1

During periods of very cold weather, additional birds arrived from other local sites and, for a short period in January 1984, the number of birds present on the reserve more than doubled (to a total of 16). The newly-arrived birds attempted to establish their own territories and devoted up to half of their time to boundary disputes, far in excess of that of the residents. When the weather conditions improved the additional birds left the reserve.

Territorial disputes

During the autumn and early winter of 1985, the research team attempted to investigate territoriality through activity watches of birds present on the lagoon at Lemsford. Every minute, each bird was scored as feeding, resting or disputing. Most watches were over at least one hour and all were completed during the period October to December. On the graph, the solid line and points are the counts of the numbers of birds, and the open symbols are the percentage of time that birds spent in dispute.

blog2 aggression graph

From early October, which corresponds to the end of the autumn moult, between 6 and 11 birds were present at Lemsford, feeding together as a group with little or no interaction. Around mid-October, the number of disputes started to increase. It varied in intensity from day to day but, over a few weeks, the numbers of birds present fell to four or five. These birds took ownership of exclusive territories that were largely maintained for the whole of the winter. Ken Smith was able to find all of the missing Green Sandpipers within 15 km of Lemsford. Some of these individuals would occasionally pop back to Lemsford, get involved in a fight and leave again. In extreme weather interlopers can spend the whole day trying to feed on the lagoons and being chased off.

Tom SpellerFrom observations at Lemsford, it appears that, once territories have been established, local birds are well aware of their boundaries and neighbours. Should a bird stray into a neighbouring bird’s patch, a low-key call is sufficient warning to avoid a disagreement. Ken reports that the big disputes, with chasing and out-and-out aggression, only occur when the territories are being established or when a new bird tries to feed in an established territory. During extremely cold weather, in the 1980s, there would be lots of extra birds attempting to feed in the spring-fed watercress beds, by trying to squeeze into perceived gaps between territories. Such cold conditions are very rare nowadays.

A changing climate

Over the three decades of the project, there has been a tendency for cold winter temperatures to become less frequent across Britain & Ireland. During this time, the distribution of Green Sandpipers has expanded northwards, as you can see in the figure below.

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The left-hand and central maps show the winter distributions of Green Sandpiper in the periods of the two winter atlases of 1981-84 and 2007-11, respectively. The surveys underpinning these maps were organised by the British Trust for Ornithology with BirdWatch Ireland and the Scottish Ornithologists’ Club. The expansion of the range represents a 56% increase in occupied 10-km squares, with an obvious extension into Scotland and across northern England, where winter temperatures are colder. Data collected for Bird Atlas 2007-11 included measures of effort, enabling relative abundance to be quantified. In the right-hand map, darker squares represent areas with higher numbers of Green Sandpipers. The Lemsford site is marked with a star.

As, mentioned earlier, there is an indication that annual return rates to Lemsford (and in the German study) relate to the conditions birds experience in the winter period prior to departure for their breeding grounds. In Scotland and Northern England, where freezing conditions occur more frequently, it might be expected that survival rates will be lower than in southern England. For winter populations to establish themselves in new (colder) sites, young birds will need to spend their first winters in these areas and then return in subsequent years. Local population can potentially grow unless or until knocked back by a cold winter.

Where to in spring?

blog2 previous.jpgIn recent years, the research team have deployed harness-mounted geolocators to ascertain the movements of a small number of individuals during the course of a full annual cycle. Another WaderTales blog discusses migration and the effects of harnesses on the behaviour of individuals. See Green Sandpipers & Geolocators.

Summary and papers

This thirty-year study is an excellent example of what can be discovered through long-term observations of a small population of waders. You can read more about the Hertfordshire Green Sandpiper research in these papers (links in bold):

  • K W Smith, J M Reed & B E Trevis (1984) Studies of green sandpipers wintering in southern England. Wader Study Group Bull, 42.
  • K W Smith (1986) Green Sandpiper. In The Atlas of Wintering Birds in Britain and Ireland, pp 222-223, Poyser, Carlton.
  • K W Smith, J M Reed & B E Trevis (1992) Habitat use and site fidelity of green sandpipers Tringa ochropus wintering in southern England. Bird Study, 39, 155-164.
  • Smith, K W, Reed, J M & Trevis, B E (1999) Nocturnal and diurnal activity patterns and roosting sites of Green Sandpipers Tringa ochropus wintering in southern England. Ringing & Migration, 19, 315-322.
  • Smith K W (2002) Green sandpiper in The Migration Atlas: movements of the birds of Britain and Ireland. Wernham C V, Toms M P, Marchant J H, Clark J A, Siriwardena G M & Baillie S R. (eds). T & A D Poyser, London.
  • Smith, K.W., Trevis, B.E. & Reed, M. (2018). The effects of leg-loop harnesses and geolocators on the diurnal activity patterns of Green Sandpipers Tringa ochropus in winter. Ringing & Migration 32: 104-109.

 


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.

 

WaderTales blogs in 2018

RP no geolocatorThe amazing migrations of Ringed Plover, concerns about Spotted Redshank and lessons from Little Tern conservation …

just three of the highlights from WaderTales in 2018.

Seventeen new WaderTales blogs were published during the year, bringing the total so far to 65. There are three articles about Black-tailed Godwits (total now 16), two more focusing upon Icelandic research (total 8) and lots of new single-species and conservation-related tales to catch up on. The most widely-read blog is a review of global survival rates in waders and the least popular (so far) is one that looks at site fidelity in breeding Black-tailed Godwits.

morgan 2018Black-tailed Godwits

There are several WaderTales blogs about the expanding population of islandica  Black-tailed Godwits and the fast-disappearing limosa birds. This year, it was a pleasure to report on the success of ‘head-starting’ as a means of boosting the British breeding limosa population.

  • Just one Black-tailed Godwit tells one godwit’s life story for the three years after ringing, using observations by birdwatchers in four countries.
  • Site-fidelity in Black-tailed Godwits looks at how the head-starting programme to support the East Anglian population of limosa might be affected by philopatry.
  • Head-starting Success reports on the joint RSPB/WWT project to increase the Black-tailed Godwit breeding population in the Nene, Ouse & Welney fens.

blog whimbrelIceland-based research

The range of wader research in Iceland has expanded over the years and these blogs give a taster of the the breadth of the work.

blog stalkingSingle-species studies

This section is a bit of a miscellany. Each blog is focused on a particular species and is usually based on a scientific paper that highlights a broader issue of conservation importance.

  • Well-travelled Ringed Plovers from Chukotka in north-east Russia spend the winter in Somalia, Egypt, the Red Sea & the Persian Gulf.
  • Green Sandpipers and Geolocators summarises a Ringing & Migration paper about changing behaviour patterns in Green Sandpipers that wore geolocators.
  • Fewer Spotted Redshanks reviews migration patterns and changes in abundance of the species, in a British & Irish context.
  • Starting moult early focuses on the timing of moult in Golden Plover populations. It turns out that it’s tough to find a three-month period in which to moult.
  • Iceland to Africa, non-stop discusses the speed of migration of Icelandic Whimbrel in spring and autumn.

malpasIssues in wader/shorebird conservation and science

Waders across the globe are subject to huge pressures, with several species close to extinction. In some areas we are seeing reduced annual survival – which is a serious issue in species which were thought of as long-lived birds – and many populations are finding it hard to raise sufficient youngsters to sustain numbers.

  • Waders are long-lived birds! Some thoughts on the longevity records for BTO-ringed wader species and the value of monitoring survival.
  • Measuring shorebird survival is a global review that explores the geographic, seasonal and sex-based variation in survival rates across wader families.
  • Curlew Moon has at its heart a review of Mary Colwell’s book of the same name but also summarises some of the issues being faced by Curlew in Ireland and the UK.
  • Black-tailed Godwit and Curlew in France provides background to the debate about a hunting ban or moratorium in France.
  • Tool-kit for wader conservation provides an overview of the tools that are available to conservationists and site-managers working on wet grasslands.
  • Deterring birds of prey summarises a paper about Diversionary Feeding; one way to keep protected predators away from wader chicks.
  • Leg-flags and nest success investigates whether nesting success of small waders (shorebirds) is affected by wearing leg-flags.

Want to read more? To see a full list of the WaderTales blogs that have been published since 2015 CLICK HERE.

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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.

 

Designing wader landscapes

blog whimbrelMuch has been written about the negative impacts of agriculture on breeding birds – but farming can be good for some species. In Iceland, where high-input agriculture is relatively recent, breeding waders are commonly found in nutrient-rich environments that are associated with increased production. How can high breeding densities of waders be maintained, as farming continues to expand and intensification increases?

In her paper in Agriculture, Ecosystems & Environment Lilja Jóhannesdóttir investigates the distribution of breeding waders across landscapes with varying amounts of highly-cultivated fields and semi-natural areas. She discovers that, in some circumstances and at an appropriate level, adding cultivated land within a broader mosaic of habitats may benefit breeding waders. Is this a model system that provides clues as to how to design landscapes that can support sustainable breeding wader populations in other parts of the world?

The waders of Iceland

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Breeding populations of waders in Iceland (AEWA report)

Iceland is a hot-spot for breeding waders, holding half or more of Europe’s Dunlin, Golden Plover and Whimbrel, in a country that is a bit smaller then England. The paper at the heart of this blog is written by Lilja Jóhannesdóttir, who worked with colleagues from the University of Iceland, the Agricultural University of Iceland, the University of East Anglia (UK) and the University of Aveiro (Portugal). They investigated how different ways of increasing agricultural productivity might impact upon these species, and others such as Black-tailed Godwit, Redshank and Snipe.

Much of Iceland’s upland interior is not suitable as farmland but there is still plenty of room for agricultural expansion. Only 7% of the area between sea level and an elevation of 200 m is currently under cultivation but it is estimated that it would be possible to increase this to 63% – an eight-fold extensification. Icelandic lowlands currently comprise a fine-scale mosaic of open semi-natural habitats and cultivated fields (primarily for silage production to feed animals), making most of the landscape much more heterogeneous than in countries with a longer history of commercial farming.

blog hay and semi-naturalTwo previous WaderTales blogs have already shown that:

Given that farm production is predicted to increase, that farmers like breeding waders and that some intensively-managed fields can be attractive to waders, is it possible to design farmed landscapes that will work for birds and farmers?

Increasing inputs and reducing heterogeneity

blog nice wetlandGlobally, the expansion and intensification of agriculture has altered landscapes and the associated homogenisation has greatly influenced bird abundance and reduced biodiversity. Populations of numerous species, particularly specialist species, have declined, as agriculture has expanded, while generalist species have often thrived in agricultural habitats.

There is no shortage of examples in which highly intensively managed farmland is shown to be bad for breeding waders. In the monoculture hay-meadows of the Netherlands, Black-tailed Godwit productivity is really low, for instance. These fields have been drained, fertilised and re-sown, in order to create easily-managed carpets of single-species grass that can be cut several times a year. There is more about this in this paper by Roos Kentie.

blog hay fieldAlthough there are some areas of Iceland in which farming is quite intensive, there are many others where farmers have a lighter touch. For instance, nutrient-poor dwarf birch marshes may occasionally be grazed by sheep in the summer but these areas have never received applications of artificial fertiliser. At this end of the intensification continuum, increasing agricultural operations may have benefits for breeding waders. When a patch of rough grazing is ploughed and turned into a hay meadow, the addition of fertilisers can potentially increase soil fertility and create an attractive place for waders to feed. A hay meadow within a local area that is dominated by dwarf birch marsh could effectively increase the heterogeneity (& nutrient-richness via spill-over) of the local area, albeit in an artificial way. In the UK, Golden Plovers breeding on moorland are known to travel up to 7 km to feed on fertilised hayfields with high earthworm densities. This paper by James Pearce-Higgins & Derek Yalden in IBIS provides a nice example of how low intensity agriculture can provide resources for waders in the wider landscape.

Researching waders and landscapes

blog dbmLilja’s work in the Southern Lowlands of Iceland focused upon understanding how agriculture influences breeding wader densities and how these relationships might influence future change. At its heart were counts of adult waders encountered along 200 transects (totalling over 100 kilometres) within semi-natural habitats, visited at several stages during the breeding seasons of 2011 and 2012.

As well as counting birds, Lilja categorised habitats within 500, 1000, 1500 and 2500 metres of the transects, which she called buffer area in the paper. Interestingly, and usefully for later analyses, the distribution of different habitat types is pretty uniform across these scales, in this part of Iceland, with little substantial difference according to elevation. In the diagram below, the 200 transects (a) have been split between those below 50 m above sea level (b) and those higher than 50 m (c).

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Landscape-scale effects

To fulfill the various demands of parents and their offspring, waders need diverse resources on or near their territory. An adult can feed a kilometre or more away from its nest, between incubation bouts, and chicks are mobile from an early age. Tagging has shown that young Black-tailed Godwits can move up to 3 km in the first five days of life, just to give one example. In this open landscape, breeding success is likely to be a function of habitat availability at a broad scale. This is explored in a WaderTales blog about nesting Whimbrel.

blog redshankUsing data collected from these 200 lowland transects, Lilja was able to establish relationships between breeding wader densities and the amount of cultivated land and wetland in the surrounding landscape. These two habitat types were considered because future agricultural expansion is likely to take place on drained wetlands that have high conservation value. In her analyses she assessed the extent to which the amount of cultivated land in the surrounding landscape affects wader densities on semi-natural land, and then considered the potential effects of future agricultural expansion on wader populations. There was substantial variation in the density of all of the six most common wader species recorded on the transects, ranging from 0 to 284 birds/km2.

Lilja found that wader densities in semi-natural habitats were consistently greater when the surrounding landscapes had more wetland, at scales ranging from 500 m to 2500 m, indicating the importance of wetland availability in the local neighbourhood. However, the effects of cultivated land in the surrounding landscape varied with fertility and landscape structure, which was largely defined by altitude.

  • In fertile, low-lying coastal areas (from sea-level to 100 m altitude), wader numbers declined with increasing amounts of cultivated land (and the lowest densities occurred in areas dominated by cultivation). This suggests that further conversion of semi-natural habitats into farmland is likely to severely impact waders in low-lying areas.
  • In less fertile habitats at higher altitudes (between 100 m and 200 m), the lowest densities occurred in areas without cultivated land. This suggests that additional resources provided by cultivated land may have a more positive affect in the less-fertile, higher altitude areas.

blog blackwitThe relationships between the areas of wetland and agriculture in the surrounding landscape and the density of waders vary between species, as you can read in some detail in the paper. A few highlights are:

  • With increasing area of cultivated land, densities of Golden Plover, Dunlin and Whimbrel declined significantly at lower altitudes but increased at higher altitudes. These are the three species that would appear to respond most positively to the addition of pockets of cultivated land within a semi-natural matrix of less fertile land, that tends to be found at higher elevations.
  • Higher amounts of wetland were associated with increased densities of Dunlin and Black-tailed Godwit, but lower densities of Redshank. Golden Plover numbers were unaffected by amount of wetland in the surrounding landscape.
  • Whimbrel densities increased with wetland area, at higher altitudes. Wet patches have been shown to be very important to Whimbrel chicks, as you can read in this WaderTales blog about research in Shetland.
  • At lower altitudes, Snipe densities increased with the amount of wetland area in the local vicinity. This relationship was less pronounced at higher altitudes, which tend to be less effectively drained and hence generally wetter.

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What now?

Changes in Icelandic landscapes are to be expected in the coming years, as most farmers intend to increase their areas of cultivated land. This expansion will inevitably have impacts upon the internationally important breeding wader populations of Iceland but the level of such impact will depend on where the expansion will occur. This paper shows that increases in the area of cultivated land at lower altitudes in Southern Iceland are more likely to result in declines in wader density than in less fertile areas, when tend to occur at slightly higher altitudes (still under 200 m above sea level). An important next step will be to identify the landscape structures and scales of management that can continue to support high densities of breeding waders.

blog coastal wetlandGiven the international importance of Iceland as a home for breeding waders it would be nice to think that this paper can be used to develop national land management policies that can prevent the unintended loss of species such as Golden Plover and Snipe, which landowners value and wish to preserve. At the farm and community level, the paper highlights the key importance of maintaining the complex and heterogeneous landscapes of lowland Iceland, retaining as many as possible of the remaining wetland patches and pockets of semi-natural land within even the most intensive of farming areas.

The paper may well be of interest to conservationists who are struggling to reverse wader declines in other parts of the world. In Southern Iceland, where 7% of the land is being farmed relatively intensively within a fine scale mosaic of both wet and dry semi-natural habitats, it is possible to support hundreds of waders per square km across the wider countryside. Can this situation be replicated across large tracts of land in other countries?

Take home message and paper

blog heterogeneousThis paper provides a useful reminder that the links between land use changes and biodiversity implications can be highly context-dependent. Further agricultural conversion of wetlands and rough grazing areas in the fertile low-lying areas of Iceland is likely to be detrimental for breeding waders, but such effects may be less apparent in less fertile, higher altitude areas. Here, the conversion of some land from rough-grazing to hay meadows may provide feeding opportunities off-territory for Dunlin, Golden Plover and Whimbrel. The scale at which the addition of cultivated areas is beneficial to breeding waders has yet to be determined.

This paper is published as:

Interacting effects of agriculture and landscape on breeding wader populations. Lilja Jóhannesdóttir, Jennifer A. Gill, José A. Alves, Sigmundur H. Brink, Ólafur Arnalds, Verónica Méndez and Tómas Grétar Gunnarsson https://doi.org/10.1016/j.agee.2018.11.024

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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.

 

Iceland to Africa, non-stop

blog tagRinging had already suggested that Whimbrel might fly non-stop from Iceland to western Africa (see “Whimbrels on the move”). By using geolocators, Camilo Carneiro and his colleagues from the Universities of Iceland and Aveiro (Portugal) have now shown that this is the norm – and reveal just how quickly they get there.  In the paper reporting on this work, they contrast this rapid autumn movement with what happens on the return journey in spring.

Migratory journeys

European Whimbrel are made up of two distinct populations which mix in the wintering grounds. Three-quarters of the estimated total of 400,000 pairs breed in Iceland, with the rest breeding from Scandinavia through to Russia. In the autumn, most of the Icelandic birds fly straight to Africa. In the late summer and early autumn, the vast majority of birds seen in the UK and other European countries on the East-Atlantic Flyway are of continental (rather than Icelandic) origin. Most will continue their migrations to Africa.

Camilo Carneiro’s paper focuses on the Icelandic population. Although the breeding locations of the birds in the study all fell within a circle of radius 5 km, the wintering area represents about 1500 km of the coastal strip of western Africa and its off-shore islands. This includes Sierra Leone, Guinea-Conakry, Guinea-Bissau, Senegal, The Gambia, Mauritania and Morocco, with the highest density of the locations in Guinea-Conakry and Guinea-Bissau. On spring migration, although some manage a similar non-stop flight, most birds stopped off on their way back to Iceland. The largest number paused in Ireland, with others visiting western Britain, northwest France and Portugal. Marked birds flew an average of 6079 km in autumn and 6450 km in spring.

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A sense of urgency

Most studies show that birds migrate faster in spring than in autumn, something that may be associated with a need to get to breeding sites as quickly as possible. Potentially, this enables them to take advantage of the short window in which to find a partner, lay and hatch eggs, look after chicks and fatten up for the return journey. Why is autumn migration quicker for Whimbrel that breed in Iceland and spend the winter in countries such as Guinea-Bissau?

blog tag postCamilo Carneiro and his colleagues have been studying the migrations of individual Whimbrels using geolocators. These small devices, attached to leg-rings, record the times of dawn and dusk for twelve months. When (or if!) an individual can be caught again in the subsequent breeding season, the geolocator can be removed and the data down-loaded, revealing a year’s worth of movements. One of the fascinating things about this study is that there are 56 migrations from 19 individuals; meaning that there are several birds for which repeat information has been collected. There’s a WaderTales blog about geolocators here (Are there costs to wearing a geolocator?)

The tags used on these Whimbrels did not just measure light levels, they also recorded temperature and whether the tag was wet or dry. These extra data helped to establish more precisely the periods in which birds were on migration, as air temperature is lower at higher altitudes and tags can only record wetness if birds are standing in water. Please see the paper and supporting materials for details of the methodology. Given that birds cannot fly without fuel, account is taken of the time taken to fatten up for migration, when estimating the whole migratory period.

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Wintering Whimbrel in Guinea-Bissau

Results

The paper by Camilo Carneiro in the Journal of Avian Biology provides details about the wintering and staging location of Icelandic Whimbrel but the main focus is on speed of migration. This was calculated as the ground distance travelled divided by migration duration, where this period includes fuelling time.

  • blog flightAll birds flew directly from Iceland to the wintering sites (30 autumn migrations from 19 individuals), a journey of four or five days.
  • Males departed earlier than females in spring and made a stopover in 83% of the cases (15 out of 18 individuals), while females stopped on 75% occasions (6 out of 8).
  • Migration duration (fuelling plus flight times combined) was significantly different between seasons, being 59.2 ± 6 days in autumn and 65.5 ± 6.2 days in spring, with no apparent differences between sexes.
  • Migration speed and ground speed were higher in autumn than in spring (migration speed: 102.6 ± 2.2 kmd-1 in autumn and 98.6 ± 5.3 kmd-1 in spring; ground speed: 16.50 ± 5.99 ms-1 in autumn and 13.07 ± 5.82 ms-1 in spring), with no differences between sexes.
blog tag in grass

Catching an individual Whimbrel, in order to remove its geolocator, becomes harder every year. A range of methods is used to catch birds on their nests.

With only a small sample, the following reported results were not statistically significant:

  • On average, males departed later than females on autumn migration. This makes sense, as males stay with their chicks longer than females.
  • In spring, males arrived into Iceland on average 2 days before females.

Explaining the patterns

The discussion section of the paper provides a fascinating review of some of the theories relating to migration physiology – it’s well worth a read. This is just a quick summary.

Autumn migration seems relatively straightforward; every tracked Whimbrel took a direct flight from Iceland to Africa. For Whimbrel migrating to Iceland from western Africa in spring, however, there seems to be a relatively small chance of being able to fly all the way in one hop (5 out of 26 northward flights were direct). The authors suggest that:

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    Whimbrel roosting in the top of mangroves at high tide

    When leaving Iceland at the end of the summer, Whimbrel are heading towards predictable resources which will be similar from week to week. Timing of departure is not critical and birds may be able to wait for helpful weather patterns.

  • On the journey south, wind conditions are generally more favourable than on the journey north, reducing the duration of direct flight.
  • Some birds may have sufficient resources for the northward flight, if weather conditions are helpful, but choose to stop off in western Europe (particularly Ireland) if the fuel gauge suggests that they might not be able to complete the crossing.
  • It is possible that the relatively recent addition of West African Bloody Cockles to the Whimbrel’s diet, in the Banc d’Arguin, may have improved the species’ capacity to fatten up quickly, increasing the possibility of a one-flight trip north.
  • Staging areas in western Europe, particularly Ireland, may provide relatively predictable resources that can be used to top-up reserves for the final 1500 km crossing of the Atlantic in spring. By using a stop-over, it may be possible to take on extra reserves that can be used in the early part of the breeding season.
  • There may be a stronger link between weather patterns in western Europe and Iceland than between western Africa and Iceland. Whimbrel that stop off in Ireland, or other countries on the Atlantic seaboard, may then depart in weather systems that are also associated with warmers spring conditions in Iceland.

blog no ringThere are many questions still to be answered but one thing is certain; as it says in the title of the paper, when the migration of the Icelandic Whimbrel is studied in detail, it is clear that there is faster migration in autumn than in spring. Here’s a link to the paper:

Faster migration in autumn than in spring: seasonal migration patterns and non‐breeding distribution of Icelandic Whimbrels Numenius phaeopus islandicus Camilo Carneiro, Tómas G. Gunnarsson & José A. Alves Journal of Avian Biology 10.1111/jav.01938

More about migration

Migrating birds make ‘decisions’ on timing and staging each year that can affect their personal survival and the chance of successfully raising young. Are these ‘strategies’ just the consequences of the circumstances that arise in a particular season? As scientists gather longer runs of tracking data on individuals, and can relate these to wind and weather patterns, it may be possible to gain a better understanding of the drivers of migratory patterns.

The team behind this paper (Camilo Carneiro, Tómas Gunnarsson & José Alves) have produced a number of complementary papers on wader migration, some of which have been covered in previous blogs:

WaderTales: Overtaking on Migration.  Alves, J. A., Gunnarsson, T. G., Potts, P. M., Gélinaud, G., Sutherland, W. J. and Gill, J. A. 2012. Overtaking on migration: does longer distance migration always incur a penalty? – Oikos 121: 464–470.

IBIS/BOU: Risking it all in a direct flight.  Alves, J. A., Dias, M. P., Méndez, V., Katrínardóttir, B. and Gunnarsson, T. G. 2016. Very rapid long-distance sea crossing by a migratory bird. – Sci. Rep. 6: 38154.

Gunnarsson, T. G. and Tómasson, G. 2011. Flexibility in spring arrival of migratory birds at northern latitudes under rapid temperature changes. – Bird Study 58: 1–12.

WaderTales: Whimbrels on the move.  Gunnarsson, T. G. and Guðmundsson, G. A. 2016. Migration and non-breeding distribution of Icelandic Whimbrels Numenius phaeopus islandicus as revealed by ringing recoveries. – Wader Study 123: 44–48.

WaderTales: Black-tailed Godwit pairs – the importance of synchrony.  Gunnarsson, T. G., Gill, J. A., Sigurbjornsson, T. and Sutherland, W. J. 2004. Arrival synchrony in migratory birds. – Nature 413: 646.

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The southern lowlands of Iceland (breeding grounds of Whimbrel) seen from Þríhyrningur

 


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.