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 protection 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

Waders are long-lived birds!

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

Redshank

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

Just to put records for British & Irish waders into context, the record for seabirds was set by a Manx Shearwater, at 50 years 11 months and 21 days, for waterfowl it’s a Pink-footed Goose (38 years 7 months and 7 days) and the longevity record for a passerine was set by a Rook (22 years 11 months 0 days).

This blog summarises records from the BTO Ringing Scheme between 1909 and 2017. These longevity records might be useful for a bird club quiz but they tell us very little about the health of wader populations. The real thing that is of interest is survival rates. Measuring the proportion of adult birds that survive through until the next year turns out to be exceptionally important to our understanding of wader conservation. There will be more about this later.

Records from the BTO scheme

2017 tableThe list of records alongside is taken from the Online Ringing Report, produced by the British Trust for Ornithology. (The link to the longevity records can be found at the bottom of the web-page). The report covers all birds ringed and/or reported in Britain & Ireland up until the end of 2017. I aim to update this blog shortly after each new annual report is published.

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

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

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

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

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

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

Getting old

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

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

Survival

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

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

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

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

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

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

Please help to measure survival rates

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

 


 GFA in Iceland

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

@grahamfappleton

 

 

 

 

 

Wetland Bird Survey: working for waders

Red-listed Curlews, Scottish Oystercatchers, a boom in Black-tailed Godwits and the need for safe roost sites. Here’s a selection of WaderTales blogs that may appeal to counters who contribute to the UK Wetland Bird Survey (WeBS) and other birdwatchers who like waders/shorebirds.

Blog RINGOS

It’s 70 years since UK birdwatchers started to count waders and waterfowl and there are now over 3000 registered Wetland Bird Survey volunteers.

The work that volunteers do to chart the rises and falls of species as diverse as Redshanks and Whooper Swans provides a unique insight into the fortunes of our wintering waterbirds. As a tribute to the people behind the binoculars and telescopes, I highlight seven WaderTales articles that use WeBS data. Click on the links in bold if you want to read a particular story. Link to latest WeBS report.

Curlew counts

curlew

WeBS counts for Curlew in Great Britain between 1974 and 2016

In the blog Is the Curlew really near-threatened? WeBS counts are used to show how numbers have changed over the decades. There might have been a boost in numbers when Curlew came off the hunting quarry list in Great Britain in 1981 but declines in the last 15 years reflect issues birds face in the breeding season in many parts of their European range.

Internationally, Eurasian Curlews are classified as near-threatened and in the UK they are now red listed. WeBS counts in Northern Ireland, alongside I-WeBS counts in the Republic, were successfully used to argue for the cessation of shooting across the island of Ireland in 2012.

Scottish Oystercatchers

L17A9623 (2)

Oystercatchers are unusual, amongst waders, in that they feed their young

Surely the Oystercatcher is one wader species that we don’t need to worry about? Although the blog Oystercatcher: from shingle beach to roof-top leads with nesting behaviour, WeBS counts are used to illustrate regional trends in different parts of the United Kingdom. In Scotland, there is concern about poor breeding success, while in parts of Wales and England, WeBS counts may provide a way of measuring the population-level effects of cockle fishing and diseases affecting shellfish.

oyc webs

Three very different trajectories for national WeBS counts for Oystercatchers since 1974

Mid-winter movements

figureThe annual WeBS report highlights the months in which counts are at their highest in different estuaries. For Knot, for instance, the highest counts on the Wash are in September, in other east-coast estuaries and on the Dee the peak is in December, whilst further north, in Morecambe Bay and the Solway, top numbers occur in January and February.

In Godwits & Godwiteers, which focuses on the superb work of observers who track the movements of colour-ringed Black-tailed Godwits, WeBS counts from east coast estuaries and the Ouse Washes illustrate the move inland that occurs as the winter progresses.

National patterns and local counts

blogGroups of WeBS counters who cover local estuaries will be the first to notice changes in the numbers of the key species that use their own sites. If the number of Dunlin drops, is that a local phenomenon or part of a national picture? Is there always a strong link between national declines (or increases) and site-based counts? Interpreting changing wader counts provides some answers. It emphasises just how reluctant waders are to change wintering sites between years.

High-tide roosts

horse-and-flockEvery WeBS counter will appreciate the value of a safe (undisturbed) roosting site, whether this be used by waders or by ducks and geese. In A place to roost, WeBS counts for Black-tailed Godwits are used to assess the national and international importance of an individual roosting site in northwest England. The main thread, however, is about the energy expenditure associated with sleeping (not very much) and travelling to and from a safe roost site (lots). An interesting add-on is the story of what happened to Cardiff’s Redshanks when the estuary was turned into a lake.

New recruits

If adult birds don’t change their winter homes then increases in local populations may well reflect good breeding years for wader species. 2017 was a good year for several species that breed in Iceland, particularly Black-tailed Godwits. T with BTGA great summer for Iceland’s waders puts the year’s productivity into context and gives an update on wader research that is being undertaken by the South Iceland Research Centre (University of Iceland), the University of East Anglia (UK) and the University of Aveiro (Portugal). If you have ever seen a colour-ringed Black-tailed Godwit, Ringed Plover, Oystercatcher or Whimbrel you may well find this interesting.

On the open shore

NEWS tableThe blog News & Oystercatchers was written to promote the Non-estuarine Waterbird Survey of 2015/16, or NEWS-III. There are a lot of waders on the shorelines that link the estuaries that are covered for WeBS and, every few years, volunteers are asked to count these birds. In NEWS-II (2006/07), it was estimated that 87% of Purple Sandpipers were to be found on the open shore (see table) with high numbers of several other species. There’s an initial assessment of the results for NEWS-III in the 2016-17 WeBS report and I look forward to writing up the results as a WaderTales blog, once a paper is published.

Links to blogs mentioned already

Many more to choose from

There are over 40 WaderTales blogs to choose from in this list. Four of these articles might be of particular interest to WeBS counters:

  • knot

    Knot migration

    Which wader, when and why? gives an overview of the migration of waders into, out of and through Britain & Ireland. The patterns help to explain why the peak numbers for Sanderling occur on the Wash in August, on the Dee in November and on the North Norfolk coast in May, for instance.

  • Bar-tailed Godwits: migration & survival  contrasts the different migration patterns of the two races of Bar-tailed Godwits that use British & Irish estuaries and explains the importance of colour-rings in the calculation of survival rates. On the other side of the world, Wader declines in the shrinking Yellow Sea shows how quickly numbers can change if the annual survival probabilities of adults fall. sum plum
  • The not-so-Grey Plover focuses on the Grey or Black-bellied Plover but the real story is about moult. British and Irish estuaries are important to huge numbers of moulting waders. WeBS counters often don’t have time to look at individual birds but, with the right camera, you can learn a lot about waders by checking out the right feathers.

Thank you

Blog Counter 1I use WeBS data a lot – in my blogs and in articles – and I appreciate the tremendous value of data collected each month by thousands of contributors. They monitor the condition of their local patches and have directly contributed to local, national and international reviews of the conservation status of wintering waterbirds. To every current and past WeBS counter – ‘thank you!’

There’s a (large) selection of papers using WeBS data here, on the BTO website. The Wetland Bird Survey is run by the BTO, in partnership with RSPB and JNCC (which acts on behalf of NE, NRW, SNH & DAERA), and in association with WWT.


 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

Wader declines in the shrinking Yellow Sea

An important paper by Colin Studds and colleagues shines a spotlight on the Yellow Sea, where waders/shorebirds have lost vast areas of feeding habitat during China’s economic boom.

headerWaders make some of the most remarkable migratory journeys in the bird world and many rely on a few key estuaries to refuel, especially as they head north to breed. For hundreds of thousands of waders on the East Asian-Australasian Flyway, from tiny Red-necked Stints to Far Eastern Curlews, the Yellow Sea is absolutely crucial. A new paper by Colin Studds and sixteen colleagues collates the available information on current population trends of waders using this flyway and shows how these relate to the reliance of each species on the Yellow Sea. The more a species relies on disappearing mudflats, between China and the Korean peninsular, the faster it is declining.

As Colin Studds says: “Scientists have long believed that loss of these rest stops could be related to the declines, but there was no smoking gun.” Now there is. The new paper is published in Nature Communications.

Rapid population decline in migratory shorebirds relying on Yellow Sea tidal mudflats as stopover sites (Nature Communications 8:14895 | DOI: 10.1038/ncomms14895)

Establishing the routes

barwit

Bar-tailed Godwits make epic migratory journeys

Over the last twenty years, satellite tracking has revealed the amazing migratory journeys of shorebirds on the East Asian-Australasian Flyway. The most famous wader ever must be E7, which was the first Bar-tailed Godwit to be tracked from Alaska to New Zealand in one continuous journey, covering the 11,600 km journey in 9 days. When E7 flew from New Zealand to the Yellow Sea in the next spring, on the first leg of its return journey, that was another flight of 10,200 km in 7 days.

It’s not just Bar-tailed Godwits that link New Zealand and Australia to the Yellow Sea. Colour-ringing has established that at least 10 wader species use this staging area during their northward migration in spring.

Counts by Birdwatchers

FE Curlew standing

Far Eastern Curlew is one of the fastest declining species on the flyway. There is a WaderTales blog about the global plight of members of the curlew/godwit family here.

Annual counts of waders have been taking place in sites across Australia and New Zealand since the early 1980s. Colin Studds and his colleagues use data collected during the non-breeding seasons between 1993 and 2012 from 43 of these key locations. The analysis relies on the work of scores of volunteer birdwatchers who undertake these counts during the months from October through to March. The count data used in this paper focused on December and January, when there is least likelihood of within-season movement. Some of the declines have been dramatic; in twenty years, the number of Far Eastern Curlew fell by about 60%, with a 75% drop in Curlew Sandpipers, just to give two examples.

If numbers are going down, then that suggests that these waders are failing to breed as successfully as they once did or that the adults themselves are dying in larger numbers than used to be the case – or both. The fact that no changes have been observed in the proportion of juveniles in flocks strongly suggests that survival rate is the key demographic parameter upon which to focus when trying to understand population declines.

Declining survival rates

Colour-ring observations not only establish migratory links, they also provide the raw data from which annual survival rates can be estimated. A typical annual survival rate for an adult wader is between around 70% and 90%. If the survival rate is 90%, and 50 female waders lay an average of 4 eggs during a breeding season, then only 10 of the chicks need to hatch and reach breeding age for the population to remain stable. If that same level of productivity occurred but the survival rate for adults changes to 80%, then the chance of an adult dying in any given year doubles and the population will drop by half in just six years. This illustrates that a fall in survival of just 10% can have serious implications for the population trajectory.

great knot

Changing Great Knot survival from 86% to 68% could reduce life-expectancy by two-thirds

The counts of non-breeding waders in Australia suggested that there were major changes in numbers for several species between 2010 and 2012. When Theunis Piersma and colleagues analysed the colour-ring sightings for populations of three species that spend the non-breeding season in Australia and breed in eastern Siberia – Bar-tailed Godwit, Great Knot and Red Knot – they discovered a decline in annual survival of between 18% and 19% in just two years. Their paper raised serous alarm bells. All three populations spend time in the Yellow Sea on their spring migration and Theunis argued that rapid habitat loss in the Yellow Sea was the most likely explanation of reduced summer survival, with dire (but uncertain) forecasts for the future of these flyway populations.

survival table

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

Reliance on the Yellow Sea

plate1-melville-barwits-under-assault

Bar-tailed Godwits watch on as their habitat disappears (Dave Melville)

It is estimated that nearly 30% of Yellow Sea tidal mudflats have been lost to coastal development in the last 30 years and China is forecast to undergo up to 14% expansion in urban development over the next 15 years, much of it concentrated on the margins of the Yellow Sea. Within the remaining mudflats, there have been increases in algal blooms, heavy metal deposits and areas of invasive Spartina alterniflora, the last of which reduces mudflat availability. All of these changes have the potential to put huge pressures on waders that are fattening up for the last leg of their migratory journey to arctic breeding grounds.

Previous work focused on waders in Japan, by Tatsuya Amano and colleagues, had shown that wader species relying on the Yellow Sea while on migration are declining more quickly than those that are not but Japan is on the migratory flyway so this result could have been confounded by changes in migratory route. By using data from the the non-breeding season and looking at a wider range of species, Colin Studds and his colleagues have been able to link reliance on the Yellow Sea with the magnitude of population changes.

Main graphA key element of the new paper is the compilation of available data on flyway population sizes, migratory connectivity and Yellow Sea count data, in order to estimate the proportion of each species that rely upon the Yellow Sea. At the lowest end is the Grey-tailed Tattler, only 3% of which use the area, whilst 100% of the menzbieri subspecies of Bar-tailed Godwit rely on the Yellow Sea. When reliance is plotted against annual population trend the fit is remarkable. Interestingly, there are two very similar subspecies in the analysis; whilst the menzbieri Bar-tailed Godwits are estimated to have been declining by 6.1% per annum, the baueri subspecies, which is only 50% reliant on the Yellow Sea, has ‘only’ been declining at 1.4% per annum. 

Emerging Conservation Action

Good newsThis paper provides further evidence of the huge importance of the Yellow Sea. To quote Richard Fuller, the team leader of this research “Every country along the migration route of these birds must protect habitat and reduce hunting to prevent the birds declining further or even going extinct.”  Issues facing birds that use the flyway are being successfully highlighted by the East Asian-Australian Flyway Partnership. Australia has signed agreements with China, Korea and Japan to protect migratory birds, and China and South Korea have recently begun the process of listing parts of the Yellow Sea as World Heritage Sites. As well as development controls, a range of mitigation actions are discussed in the paper – let’s hope that they are pursued with enthusiasm.

Update – January 2018

“Great news for shorebirds! China to halt coastal land reclamation”. Read more in this BirdLife International article.

The paper is free to download

GK flockThe results of this study have been published as Rapid population decline in migratory shorebirds relying on Yellow Sea tidal mudflats as stopover sites (Nature Communications 8:14895 | DOI: 10.1038/ncomms14895)

The authors are: Colin E. Studds, Bruce E. Kendall, Nicholas J. Murray, Howard B. Wilson, Danny I. Rogers, Robert S. Clemens, Ken Gosbell, Chris J. Hassell, Rosalind Jessop, David S. Melville, David A. Milton, Clive D.T. Minton, Hugh P. Possingham, Adrian C. Riegen, Phil Straw, Eric J.Woehler & Richard A. Fuller.


 GFA in Iceland

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

@grahamfappleton

 

Why are we losing our large waders?

A review of the global threats to the world’s Numeniini (curlews, godwits & Upland Sandpiper) does not make for good reading.

gambia-whimbrel

Icelandic Whimbrel in the warm conditions of The Guinea-Bissau

It is estimated that hundreds of thousands of Eskimo Curlews were migrating the full length of the two American continents 150 years ago – but the species is now probably extinct. The Slender-billed Curlew, its old-world cousin, is elusive at best and extinct at worst. According to the most recent global figures (as reported to the Convention on Migratory Species 11th Conference of the Parties, details below), there are estimated to be only 10,000* remaining Bristle-thighed Curlews, 32,000 Far Eastern Curlews and 77,000 Hudsonian Godwits. Why are we losing our large waders?

(Update* – Latest bristle-thighed population is now 7,000, according to BirdLife DataZone)

b-curlewThe perilous plight of members of the curlew and godwit families has been highlighted in WaderTales before (see Is the Eurasian Curlew really near-threatened and Dutch Black-tailed Godwit numbers down by nearly 75% for instance). Now, a group of wader/shorebird experts have analysed the wider conservation concerns for this group of large, long-lived waders. In a new review in Bird Conservation International, scientists ask if there are shared threats to the Numeniini (the Upland Sandpiper, eight curlews and four godwits). Can their findings help to explain why so many of these 13 species are at risk or, in the case of the Eskimo Curlew and Slender-billed Curlew, probably already extinct?

The Numeniini

categories2The Numeniini waders span the globe. In the table alongside you can see that the conservation status of the group covers the full range of possible levels, from Eskimo Curlew, the last definite report of which was in 1963, to six species that are listed as being of ‘least concern’ (IUCN criteria). Even these six species are far from safe, according to a new review undertaken by 35 authors, supported by expert opinion from a further 80 shorebird ecologists. The drivers that have led to the declines of several endangered and vulnerable species are already affecting others that are currently categorised as being of ‘least concern’. There’s more about these important caveats further down this blog.

The crisis for the Numeniini is worrying wader biologists, ornithologists and ecologists – and some governments. They are working together to share information, identify gaps in knowledge, drive forward new research and to push for conservation activities that can reduce the pressures on these species, and others that share the same habitats. A key output is a newly-published paper, led by the British Trust for Ornithology’s James Pearce-Higgins but with authors from almost 30 organisations across five continents, who collated knowledge from over 100 experts:

barwit-eaafp

There is already a great deal of concerted international action to save Numeniini species. This flyer was produced by the East Asian-Australasian Flyway Partnership

A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds. Bird Conservation International. ISSN 0959-2709

The authors are: JAMES W. PEARCE-HIGGINS, DANIEL J. BROWN, DAVID J. T. DOUGLAS, JOSÉ A. ALVES, MARIAGRAZIA BELLIO, PIERRICK BOCHER, GRAEME M BUCHANAN, ROB P CLAY, JESSE CONKLIN, NICOLA CROCKFORD, PETER DANN, JAANUS ELTS, CHRISTIAN FRIIS, RICHARD A. FULLER, JENNIFER A. GILL, KEN GOSBELL, JAMES A. JOHNSON, ROCIO MARQUEZ-FERRANDO, JOSE A. MASERO, DAVID S. MELVILLE, SPIKE MILLINGTON, CLIVE MINTON, TAEJ MUNDKUR, ERICA NOL, HANNES PEHLAK, THEUNIS PIERSMA, FRÉDÉRIC ROBIN, DANNY I. ROGERS, DANIEL R. RUTHRAUFF, NATHAN R. SENNER, JUNID N. SHAH, ROB D. SHELDON, SERGEJ A. SOLOVIEV, PAVEL S. TOMKOVICH and YVONNE I. VERKUIL

A model for collaborative conservation research

Identifying the causes of the problems of the Numeniini is not easy. Species such as the Little Curlew breed in some of the most remote areas of the world, whilst the wintering areas of Bristle-thighed Curlews are spread across the Pacific islands. Understanding the full annual cycle requires international cooperation, willingly provided by scientists and volunteer ornithologists who share a common concern about these species.

iwsgOne of the key elements of the paper-production process was a workshop at the 2013 International Wader Study Group conference in Wilhelmshaven, Germany. This was led by Nicola Crockford, Principal Policy Officer at RSPB, James Pearce-Higgins (BTO), Daniel Brown (RSPB), David Douglas (RSPB) and Jennifer Gill (University of East Anglia). It was preceded by a questionnaire survey of experts throughout the world, conducted by Daniel Brown and funded by RSPB. This two-stage process brought together information relating to population trends, demographic parameters (e.g. nesting success and survival rates) and actual/potential conservation threats.

cop11James, Dan and David refined the summary, bringing it together as a ‘Conservation Statements for Numeniini Species’ which was presented to the 11th Conference of the Parties of the Convention on Migratory Species in Quito, Ecuador in 2014 (CMS COP11). This report, authored by Daniel Brown, Nicola Crockford and Robert Sheldon and published on behalf of BirdLife International and the International Wader Study Group is available here.

In the figure below you can see a snapshot of the range of information that is available in the Conservation Statements, in this case for Black-tailed Godwit . In particular, this COP11 document provided background information for two species for which CMS Concerted and Cooperative Actions were being proposed – Far Eastern Curlew and Bar-tailed Godwit. It also painted a backdrop to the CMS Programme of Work on Migratory Birds and Flyways.

cop-for-blackwit

The new BCI paper aims to highlight the crises facing the Numeniini, to outline the suite of threats to the group and to promote this collaborative form of expert-led synthesis. It contains details as to how the questionnaire and workshop sessions were organised – information that will hopefully be of use to scientists studying other groups and taxa.

Findings of the review

In order to help inform conservation management and policy responses, James Pearce- Higgins and his collaborators have reviewed the threats that members of the Numeniini face across migratory flyways. They show that most threats are increasing in intensity. This is particularly the case in non-breeding areas, where habitat loss (resulting from residential and commercial development), aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic non-native species and climate change) were identified as widely affecting breeding areas.

far-eastern-curlew

An endangered Far Eastern Curlew in Australia

Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation. Related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Based on these threats, several key actions were proposed:

Three priority actions for monitoring and research:

  • To monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites).
  • To deploy tracking technologies to identify migratory connectivity.
  • To monitor land-cover change across breeding and non-breeding areas.
eaafp

The East Asian-Australasian Flyway Partnership is a key focus for conservation action

Two priority actions focus on conservation and policy responses:

  • To identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian-Australasian Flyway).
  • To implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved.

If implemented urgently, these measures, in combination, have the potential to alter the current population declines of many Numeniini species.

What is in the BCI paper?

As well as outlining a methodology which may well provide a template for the conservation of other groups of threatened species, the paper contains a comprehensive assessment of the global and local threats faced by the Numeniini. The discussion is the largest section – covering disturbance, development, pollution, terrestrial land-use change & predation, climate change impacts & mitigation, and hunting & harvesting. It provides an opportunity to assess the scientific evidence that supports expert opinion and usefully acknowledges some key gaps worthy of further investigation (e.g. drivers of change in the Central Asian Flyway and uncertainty over the population-level impacts of disturbance).

To summarise in a few bullet points:

  • b-davemelville

    Bar-tailed Godwits in the Yellow Sea. Another large slice of mudflat disappears as a new sea-wall is built. Read more here.

    37 populations of curlews, whimbrels, godwits and upland sandpiper are assessed.

  • Of the 13 species, seven are of conservation concern (from near-threatened to possibly extinct).
  • Most of the threats identified by the expert panel are considered to be increasing in intensity, especially in non-breeding areas.
  • A greater range of threats was reported in non-breeding areas than breeding areas.
  • Numeniini using the East Asian-Australasian Flyway face the greatest number of non-breeding range threats that were identified.
  • The greatest threat, particularly in the East Asian-Australasian Flyway, appears to be the large-scale development of key passage and non-breeding sites in coastal zones.

Quite why population declines are so common and severe in the Numeniini group is not yet clear but their large body size, low breeding rate and a consequent reliance on high annual survival rates may make them particularly vulnerable to changes in land use and habitat availability across their migratory ranges. The authors hope that this publication will provide a platform for the necessary research and monitoring, to identify and address specific threats, and that continued international collaboration will help this process.

Least Concern? Not really?

The phrase ‘Least Concern’ may be misleading. Although half of the species covered in this review (6 out of 13) are still classified by IUCN/BirdLife as being of ‘Least Concern’ there are important caveats for these species within the COP11 report. Bar-tailed Godwit was classified as ‘Least Concern’ until a few months ago, when a major, sudden drop in adult survival for two populations (menzbieri & baueri) using the East-Asian Australian Flyway was reported. The current list of ‘Least Concern’ species is:

Upland Sandpiper – Declining nesting success is being recorded.

Whimbrel – Up to nine subspecies have been described, four of which are declining in number. Demographic trends are completely unknown for five subspecies.

steppe-w

Little Curlew – Population is only 180,000 and numbers may be declining.

Long-billed Curlew – Numbers appear to be stable (only 160,000) but there have been previous extinctions in 7 US states and large parts of Canada. New climate change predictions suggest major threat to breeding population.

marbled

Satellite-tracking is being used to establish migration routes and stop-over areas for several members of the Numeniini. This is a Marbled Godwit.

Marbled Godwit – Only an estimated 174,000 individuals remain. Two of the three breeding populations are made up of only 2,000 individuals each.

Hudsonian Godwit – Only an estimated 77,000 remain, with a decline in the major Canadian population, where there has been reduced nesting & fledging success.

These caveats suggest that none of the 13 species of Numeniini can be considered to be safe. The fact that the threats to the six species of ‘Least Concern’ are the same ones that have driven the other seven species further up the ‘endangered’ scale – and even to extinction – is extremely worrying.

You can read the full paper here:

A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds. James W Pearce-Higgins et al. Bird Conservation International. ISSN 0959-2709


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

Bar-tailed Godwits: migration & survival

Putting the flags out –  to learn more about one of the most amazing species of migrating wader.

Ruth banner

When we caught 505 Bar-tailed Godwits on the Wash, on the east coast of England, on 29 August 1976 we thought that we would add hugely to our knowledge of the species’ migration but we were disappointed. In just six years, by adding leg-flags to just 248 birds, the Wash Wader Ringing Group has learnt a lot more.

Forty years ago

On 29 August 1976, in the days of stubble-burning, we had covered four cannon nets with fine, black burnt chaff to hide them almost completely. We knew that the big tide would push birds off the saltings and over the sea wall, there were decoys to pull the birds into the right 1% of a vast, flat field and the weather was good. Everything was ready. I was in a one-man, cabbage-crate hide, in line with my set of two nets. I remember seeing one Redshank look at the decoys and descend, pulling down a vast cloud of over 2000 Bar-tailed Godwits. There were some concerns about birds being too close to one of the nets on my line so we fired three nets, catching 505 bar-tailed godwits and 44 other waders.

Cathy ad and juv

Juvenile with moulting adult

A catch of 505 Bar-tailed Godwits seemed like a game-changer, including 22 that were already wearing rings. 483 new birds were bound to make a huge difference to our understanding of the species’ migration patterns and survival probabilities … surely? Up until that day, the Wash Wader Ringing Group (WWRG) had ringed a total of 1136 Bar-tailed Godwits so we were adding over 40% to the total, using harder rings with a much longer life-expectancy than those added as early as 1959.

This was a moulting flock; an autumn drop in numbers and a previous recovery of a bird in Spain suggested that many birds would spend the winter elsewhere but where? As luck would have it, only one of the birds from August 1976 has ever been found abroad – a bird shot in France in February 1985. The only British recoveries have been a bird found dead in Yorkshire in November 1976 and seven birds found around the Wash between 1979 and 1999. As to subsequent recaptures, 38 birds have been caught again by the WWRG, five of which were retrapped for a third time. With all the best models in the world, these figures are not enough to give a reasonable estimate of survival and there is no way that a change in survival rate could be picked up.

It’s pleasing to report that one bird was still alive on 21 February 2003 – over 28 years after ringing – but even this is not the longevity record for a BTO Bar-tailed Godwit. That’s held by another WWRG bird that was ringed on 22 August 1974 and last recaptured on 4 August 2008 – nearly 34 years later. Perhaps one of the 1976 birds is still alive and waiting to be caught again?

Bar-tailed Godwit migration

Since the 1976 catch, WWRG has been a bit more fortunate in its foreign recoveries of metal-ringed Bar-tailed Godwit, with 2 recoveries in Mauritania, one in Guinea Bissau and another on a ship off Guinea, out of a total of 12 BTO-ringed birds found in Africa. A bird caught in Teesmouth on 13 October 1982 was in Western Sahara five days later, which may give an indication of the timing of post-moult movement. The map alongside shows the full set of BTO recoveries (purple) and foreign-ringed birds found in Britain & Ireland (orange). The dots show the westward post-breeding movement from Russia to the Atlantic coast of Europe and the onward migration of thousands of birds to Africa.

One of the fascinating things about migration is the way that different populations of the same species have developed radically different migration patterns since the last Ice Age, the global maximum extent of which was reached only 20,000 years ago. At the same time that the Bar-tailed Godwits we see in Western Europe are making relatively modest journeys west and south in late summer, some of those of the baueri subspecies are undertaking nine-day, non-stop flights from Alaska to New Zealand. The physiological processes and navigational techniques that birds on the Pacific flyway have mastered would amaze their European cousins. To read more about flyway evolution for Arctic waders, and Knot in particular, see a Review by Theunis Piersema (Journal of Ornithology, 2011).

Conservation Status

Bar-tailed Godwits are classified as near-threatened by BirdLife International and the IUCN. There are four recognised subspecies facing various threats, as shown in the species fact-sheet here. 

Sam winter gloves

Bar-tailed Godwits wintering on the Wash are of the lapponica subspecies

Two subspecies visit the Wash Special Protection Area (SPA); lapponica from Norway through to western Siberia and taymyrensis from central Siberia. Two subspecies, menzbieri and baueri, use the East Asian-Australasian Flyway and are both undergoing extremely rapid declines, in large part due to severe habitat loss in the Yellow Sea. As a result of severe problems for waders using this flyway, the species has been uplisted to Near Threatened (BIrdLife International).

Satellite-tagging has revealed the impressive trans-oceanic migration routes of individuals between Alaska and New Zealand and shown the importance of the Yellow Sea for birds as they return north in the spring. Colour-rings and flags have shown that there has been a sudden drop in survival rates for Bar-tailed Godwits and other species using sites in China and other rapidly developing countries of South-East Asia, leading to urgent calls for conservation initiatives at an international scale. You can read more about this emerging story in these three papers.

Picture1

Learn more about the amazing migration of Bar-tailed Godwits on the New Zealand Science Learning Hub

Contrasting extreme long-distance migration patterns in bar-tailed godwit Limosa lapponica. Phil Battley et al. Journal of Avian Biology. 10.1111/j.1600-048X.2011.05473.x 

Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Theunis Piersma at al. Journal of Animal Ecology. 10.1111/1365-2664.12582

Declining adult survival of New Zealand Bar-tailed Godwits during 2005–2012 despite apparent population stability. Jesse Conklin et al. Emu. http://dx.doi.org/10.1071/MU15058

For Bar-tailed Godwits wintering in western Europe there is currently less immediate conservation concern, although there are warming conditions in their breeding grounds and over-fishing and emerging diseases of shellfish are known to be affecting estuaries on both sides of the North Sea. Things are more worrying in West Africa, where numbers have declined from 746,000 to 498,000 over a period of 30 years, according to a report by van Roomen et al. Some of these birds spend time in the Wash in the autumn on their way south.

Status of coastal waterbird populations in the East Atlantic Flyway. With special attention to flyway populations making use of the Wadden Sea. van Roomen et al.

Flying the flag

Cathy gluing

Each bird wears a two-letter flag and a white colour-ring (shown here)

Given the worsening conservation status of Bar-tailed Godwits and the gaps in our understanding of what is happening to birds that visit the Wash SPA, the WWRG decided that it would help if birds could be monitored through colour-ringing. That way, the movement and survival of individuals can be monitored using a telescope instead of relying on recapture.

The flagging of Bar-tailed Godwits on the Wash has dramatically increased the number of records of birds subsequent to ringing but the scheme is still in its early days. Flagging started in August 2010 but the first significant catch did not take place until 11 February 2012, when 56 birds was flagged. According to Phil Atkinson, who runs the WWRG database for the species, one third of the birds from this catch have been resighted alive in the four years since that catch (compared to 1% recapture rate for metal-ringed birds in the four years after the 1976 catch).

Cathy KAMost resightings have been on the Wash and those from elsewhere have tended to confirm what was known from metal ringing. A moulting bird on the Wash was seen on the Wirral (northwest England) in the same autumn, showing that birds moulting on the Wash can move elsewhere in Northwest Europe to winter. A non-moulting bird, caught at Terrington on 30 September 2011, was resighted at Ebel Khaznaya, Mauritania 50 days later. These two resightings confirmed that the Wash is an important site not only for the wintering Fenno-Scandinavian and western Siberian lapponica breeding populations but also central Siberian taymyrensis birds, that pass through in autumn to wintering areas in West Africa. The majority of overseas records have come from the Wadden Sea in spring and autumn, when birds have been on return passage to the breeding areas. There’s a 1996 summary of migratory movements of metal-ringed WWRG birds here:

The origins, moult, movements and changes in numbers of Bar-tailed Godwits Limosa lapponica on the Wash, England, Bird Study.  http://dx.doi.org/10.1080/00063659609460996 

Aivar Estonia

UV was spotted in Estonia in August 2012

By the end of 2015, 248 Bar-tailed Godwits had been colour-ringed and 92 of them seen again, many locally on the Wash. These high resighting rates are a consequence of focused searches by WWRG members and reports from birdwatchers submitting their records to sightings@wwrg.org.uk. Over the next few years it will be possible to estimate annual survival probabilities and to monitor how these change in the medium to long term. As was shown in the Yellow Sea, spotting a dramatic drop in colour-ring return rates provides evidence that development pressures are having an impact upon migratory species. Worsening conditions in the breeding grounds or wintering areas could well be detected through a more gradual but no less serious reduction in survival rates.

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


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