Should Black-tailed Godwits cross the Sahara?

Are Dutch-breeding limosa Black-tailed Godwits that now winter in Spain and Portugal doing better than ones that travel to the other side of the Sahara?

Changing weather patterns and land management are providing opportunities for many bird species to modify their migration patterns – both in terms of space and time. Dutch limosa Black-tailed Godwits were traditionally thought of as long-distance migrants that spent the winter months in countries such as Senegal and Guinea Bissau. In recent years, however, increasing numbers have been observed to fly no further south than Spain and Portugal, where their winter distribution overlaps with the islandica race.

Fewer Black-tailed Godwits  return to The Netherlands each spring

As has been described in a previous blog (Dutch Black-tailed Godwits numbers down by nearly 75%), the limosa population in western Europe is in serious decline. The proportional change is therefore even more impressive than the change in numbers. Márquez-Ferrando et al showed that the number of birds wintering in the Doñana Wetlands, Spain has increased from 4% of the flyway population in the late 1980s to 23% in 2011.

The annual distances travelled by African-wintering and Iberian-wintering Black-tailed Godwits are hugely different, being about 10,000 km and 4,000 km, respectively. A Doñana bird therefore needs to find much less fuel for migration when compared to  a bird in Guinea-Bissau.

Flamingos for company in Spain

Logic might suggest that travelling less far should have benefits. Provided that an Iberian bird survives the winter, it should be better placed at the start of the next breeding season? There’s less far to travel to return home and it might be easier to use weather cues in Spain & Portugal to determine the best time to make the journey, given that Atlantic lows affect the weather patterns across large sections of western Europe?

In a paper in Ecology & Evolution, Rosemarie Kentie and her colleagues investigate whether there are differences in timing of breeding and breeding success between Black-tailed Godwits that spend the winter in Africa and those that only travel as far as Iberia. Do European wintering birds start breeding earlier, do they choose the best breeding territories and do they have a higher chance of successfully raising chicks?

Timing of arrival

Maroune, Khady Gueye, Jos Hooijmeijer, Haije Valkema & Idrissa Ndiaye in Guinea Bissau

This paper benefits hugely from colour-ring sightings made in both African and European wintering areas. Most of these have been collected by dedicated teams but additional reports by other birdwatchers are also gratefully acknowledged. Their efforts distil into 180 known Iberian-winterers and 131 known African-winters.

When the spring arrival dates of males and females of the two groups were compared, Rosemarie Kentie discovered that African winterers arrive back two days earlier than Iberian winterers and that males return to the breeding grounds three days earlier than females (see table). Mean lay date of first egg was five days earlier for African birds.

Mean spring arrival dates

Although the magnitude of the differences seem quite small, the results are statistically significant and previous work has shown strong effects of timing of breeding on reproductive success. What is clear is that birds that only have 2,000 km to travel are no earlier (and  on average are actually later) than birds that travel 5,000 km. Both groups spend several weeks together in Iberian rice fields, before heading north, but a difference based on wintering location is still detectable.

Interestingly, this pattern of timing is similar to that previously found by José Alves and colleagues for islandica Black-tailed Godwits. In islandica, there is a much smaller wintering range, from Iberia in the south to Scotland in the north. Despite the longer journey back to Iceland from Portugal, these southern birds tend to reach Iceland about five days earlier than birds wintering in England. The energetic constraints of birds wintering in (and migrating from) different parts of the range are discussed in the paper Overtaking on migration: does longer distance migration always incur a penalty? or you can read this WaderTales blog: Overtaking on Migration.

Breeding success

Rocio Marquez-Ferrando rings an adult Black-tailed Godwit on the Dutch breeding grounds

In the limosa paper, the authors look for different measures of breeding success for Iberian and African winterers. There seems to be no link between wintering area and the quality of the territory in which birds breed, although the earlier birds may have had earlier access to better territories (see paper for details). There’s no difference in size between birds in the two groups and the daily nest survival rates were not different either. The only potential benefit for either group is that Iberian-wintering females lay slightly bigger eggs. Given that other wader studies have shown that bigger eggs turn into bigger chicks and bigger chicks are more likely to fledge, there may be a breeding advantage for birds travelling less far. This is a statistically different result (i.e. there is a measurable difference) but the magnitude is only 3% difference in egg weight, and the authors question whether this can really be significant, biologically. Is this extra mass enough to make a practical difference to the probability that these bigger eggs will turn into more, bigger or fitter youngsters?

Why are godwits now wintering in Iberia?

Fewer and fewer Black-tailed Godwits are crossing the Sahara to countries such as Guinea Bissau

We know that individual Black-tailed Godwits, like most other waders, use the same wintering areas each year. Having once settled into a particular pattern – African or Iberian – then that’s almost certainly the pattern for life. As recently as the 1980s, 96% of the western population of limosa were flying 5,000 km each autumn. The fact that few birds used the 2,000 km option then and that an increasing number do so now may suggest that winter conditions in Iberia have become more suitable for Black-tailed Godwits. This may be a good thing because there’s a line in the paper that makes for interesting reading “the mortality rate of godwits equipped with satellite tags was highest during the crossing of the Sahara Desert”.  Perhaps it’s harder to find the resources for the journey north from countries such as Guinea Bissau? That’s going to be the subject of a future paper. Meanwhile, there’s more about the satellite-tagging project on the King of the Meadows website.

Read the full paper

Does wintering north or south of the Sahara correlate with timing and breeding performance in Black-Tailed Godwits?

Rosemarie Kentie, Rocío Marquez-Ferrando, Jordi Figuerola, Laura Gangoso, Jos C.E.W. Hooijmeijer, A. H. Jelle Loonstra, Frédéric Robin, Mathieu Sarasa, Nathan Senner, Haije Valkema, Mo A. Verhoeven and Theunis Piersma. Ecology & Evolution. March 2017.

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

Waiting for the wind – spring flocks of Black-tailed Godwit in Scotland

When a flock of Black-tailed Godwit turns up on a Scottish island or lochside, in April or May, it’s probably a sign that the birds have aborted the Atlantic crossing to Iceland.

On 24 February 2017, on the Samouco saltpans on the Tagus estuary in Portugal, we saw an Icelandic Black-tailed Godwit wearing four colour-rings: red & lime on the left, green & green flag (RL-GGf) on the right. It had been ringed there on 10 August 2010 by José Alves so it’s not a surprise that it was in the same spot five and a half years later. In between times, on 29 April 2013, RL-GGf was one of 1520 Icelandic godwits counted on the Isle of Tiree, in the Scottish Inner Hebrides, by John Bowler and Graham Todd. Having encountered strong northerlies it had been forced to delay the Atlantic crossing. If you think back to the cold spring of 2013, it is not surprising that strange things happened that year. Northerlies delayed spring arrivals of African migrants in the UK but they also blocked the departure of wintering birds that were trying to fly to Iceland, Greenland and Northern Canada.

RL-GGf is one of our favourite Black-tailed Godwits. It happens to like a small estuary called Grafarvogur in Reykjavik, which Jenny Gill (University of East Anglia) and I monitor daily in the second half of April each year. We’ve seen this bird here in the springs of 2012, 2014, 2015 and 2016, on a total of 13 occasions. We have an arrival date for 2011 too, when he was spotted in Southern Iceland by Tómas Gunnarsson, our Icelandic collaborator, but there’s a gap in 2013, when we left Iceland while he was still on Tiree (see table). There are a couple of early spring records of this bird in the Netherlands, so this is where he probably spends March and early April every year, having left Portugal in February. In the last six years he has set off for Iceland in spring and only in 2013 was he seen in Scotland. He and other godwits that are forced to suspend migration are starting to give us insights into the hurdles that weather patterns can put in the way when birds are trying to travel north (Gill 2015).

Migration in a changing climate

We’ve been monitoring the spring arrival of Black-tailed Godwits in Iceland since 2000, and we’ve shown that colour-ringed birds have their own individual schedules: early birds always arrive early and late birds always arrive late. Differences in the exact date on which each individual arrives may be associated with the weather patterns each year, but individuals are remarkably consistent despite annually variable weather conditions. It therefore appears that individual godwits, like RL-GGf, have a preferred window in which to undertake the Atlantic crossing.

Interestingly, although there is no evidence that individual birds have changed their arrival times in Iceland over the last 15 years, the arrival dates of the population are getting earlier (Gunnarsson et al. 2006). We’ve shown that this advance in migration is being driven by young birds recruiting into the breeding population on schedules which are earlier than those of previous generations (Gill et al. 2015). Ultimately, this is likely to be being driven by warmer springs and earlier nesting seasons. There’s a blog about this paper. 

Black-tailed Godwits on Tiree

This Tiree Whooper Swan will also have been heading for Iceland

Over the years, the Isle of Tiree in the Inner Hebrides has proved to be a great place to pick up colour-ring sightings of Black-tailed Godwits. John Bowler, the local RSPB Officer, really enjoys watching out for their spring return when, as he comments, “hundreds can drop in on the loch-sides in full breeding dress”. The very first birds appear at the end of March and numbers increase into April, with often very large flocks occurring at the peak of passage in the last week of April and the first week of May. Birds are usually found on the grazed edges of machair lochs, with numbers declining through May and odd birds lingering to the middle of June. Given that between 1% and 2% of the Icelandic Black-tailed Godwit population wear colour-rings there is a good chance of finding a marked bird. With migration getting earlier, John’s godwit-watching season will probably get longer.

Godwits also appear on Tiree in the autumn but in smaller numbers. The first failed breeders appear in late June, followed by more adults in July and early August and then juveniles in late August through to October, with occasional stragglers in November and December. Young birds often use freshly-cut silage/hay fields on Tiree for foraging, in the same way that many will have done in Iceland as they prepared for the journey south.

Disrupted Migration

The orange flag shows that this Black-tailed Godwit had been ringed in France

Black-tailed Godwits are very site-faithful in every season of the year. However, although 63 different colour-ringed birds have been seen in spring by John Bowler and his colleagues, only one bird has been seen in more than one spring. This low number of repeat between-year sightings on Tiree, where looking for colour-ringed birds is part of the daily routine, very much suggests that birds seen here are dropping in out of necessity, rather than using the site as an annual staging post. The journey from south England or The Netherlands to Iceland is only just over 1000 miles, which is well within the capabilities for migrating waders in non-stop flight – as long as they do not encounter adverse weather conditions (Alves et al. 2012, Alves et al. 2013).

Scottish flocks of migrating Black-tailed Godwits do not only occur on Tiree, of course. On the peak day of 29 April 2013, when 1520 birds were counted on Tiree, 891 birds were also reported at Loch Gruinart on Islay. The 2411 birds in these two flocks constituted about 5% of the Icelandic Black-tailed Godwit population (Gunnarsson et al. 2005). Given that there were other colour-ringed godwits reported in Motherwell and on Benbecula, just how many Icelandic godwits were in Scotland on that day?

The lack of predictability, when it comes to the potential locations of these spring flocks, makes it difficult to monitor patterns across different years. There are simply not enough places at which there are regular counts of birds each spring and too many places where flocks could choose to stop. Fortunately, reports of colour-ringed birds provide a surrogate for flock counts.  A quick analysis of the number of colour-ringed Godwits from Icelandic, Portuguese and E England schemes, seen in Scotland between the springs of 2011 and 2016 shows that there were records in every year but with a larger number in 2015, and by far the most records in 2013. None of the birds was seen in more than one spring, emphasising the random nature of these arrivals.

The colour-ring information provided by birdwatchers is making a huge contribution to the migration studies of Black-tailed Godwits. There are now Black-tailed Godwits in Scotland in every month of the year but sightings of colour-marked individuals in April and May are particularly helpful in helping us to identify the influence of weather conditions on spring migration and the migratory routes used by birds from across the winter range. Please report any of these observations to j.gill@uea.ac.uk who will pass on records to other colour-ring administrators. Details of the godwit work and the publications to which colour-ring observations have contributed can be found in a blog called Godwits & Godwiteers.  

This article first appeared in Scottish Birds, published by the Scottish Ornithologists’ Club.

References:

Alves, J.A., Gunnarsson, T.G., Potts, P.M., Gélinaud, G., Sutherland, W.J. & Gill, J.A. (2012) Overtaking on migration: does longer distance migration always incur a penalty? Oikos 121: 464-470. DOI: 10.1111/j.1600-0706.2011.19678.x 

Alves, J.A., Gunnarsson, T.G., Hayhow, D.B., Potts, P.M., Sutherland, W.J. & Gill, J.A. (2013) Costs, benefits and fitness consequences of different migratory strategies. Ecology 94: 11-17. DOI: 10.1890/12-0737.1

Gill, J.A., Alves, J.A., Sutherland, W.J., Appleton, G.F., Potts, P.M. & Gunnarsson, T.G. (2014) Why is timing of bird migration advancing when individuals are not? Proceedings of the Royal Society of London B 281: 20132161. DOI: 10.1098/rspb.2013.2161 

Gill, J.A. (2015) Encountering extreme weather during migration: individual strategies and their consequences. Journal of Animal Ecology 84: 1141-1143. DOI: 10.1111/1365-2656.12412 

Gunnarsson, T.G., Gill, J.A., Potts, P.M., Atkinson, P.W., Croger, R.E., Gélinaud, G., Gardarsson, A. & Sutherland, W.J. (2005) Estimating population size in Icelandic Black-tailed Godwits Limosa limosa islandica by colour-marking. Bird Study 52: 153-158. DOI: 10.1080/00063650509461385

Gunnarsson, T.G., Gill, J.A., Atkinson, P.W., Gélinaud, G., Potts, P.M., Croger, R.E., Gudmundsson, G.A., Appleton, G.F. & Sutherland, W.J. (2006) Population-scale drivers of individual arrival times in migratory birds. Journal of Animal Ecology 75: 1119-1127. DOI: 10.1111/j.1365-2656.2006.01131.x

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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

Flyway from Ireland to Iceland

The Ireland to Iceland air link opens in February and does not close until well into May, as swans, geese, ducks, waders, gulls and passerines head north. At the end of June it opens again, with the first failed breeders returning to Ireland. Species such as Oystercatcher and Black-tailed Godwit spend much more of the year in Ireland than they do in Iceland.

Most Oystercatchers are being ringed with two letter engraved rings, along with two colour-rings: Photo Tómas Gunnarsson

The island of Ireland holds important populations of waders in the wintertime – everything from Grey Plovers from Siberia to Turnstones from Canada – but there is  special relationship with Iceland. It’s the next stopping off point for passage Sanderling, as they fly from Africa to Greenland, and the ultimate destination for lots of wintering birds such as Snipe, Redshank and Golden Plovers.

Oystercatchers lead the way

A lot of the Oystercatchers seen around Ireland’s coastline breed in Iceland, as has been shown by the Dublin Bay Birds Project. Birds start moving north very early, as shown by the appearance of yellow-ringed Dublin Bay birds in Tiree before the end of February each year. Migratory decisions for Icelandic Oystercatchers explains how a new Icelandic project is examining the costs and benefits of being a migrant. Irish reports of Icelandic colour-ringed birds are helping to provide answers – and the Dublin Bay birds are providing great additional data. The first paper to come out of this project is summarised in Which Icelandic Oystercatchers cross the Atlantic?

Each autumn, Irish-breeding Snipe are joined by much larger numbers from the north and east. About a quarter of foreign-ringed snipe that have been found in the island of Ireland are of Icelandic origin, compared to just one out of 255 in England. Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

Some of the later waders to use the Ireland to Iceland flyway are Whimbrels, many of which stop off in Ireland on spring migration. Whimbrels on the move summarises a paper about the movements of Icelandic, ringed Whimbrel. Since its publication, a new paper has shown that Whimbrel are able to fly between Iceland and west Africa in one jump but that they sometimes need to stop off on the way north. See Very rapid long-distance sea crossing by a migratory bird by José Alves and colleagues and Iceland to Africa non-stop by Camilo Carneiro and colleagues. Camilo has shown that individual birds leave Africa at the same time each year so it is not surprising that spring passage in Ireland is so consistent in its timing (Whimbrel: time to leave).

Black tailed-Godwits

WaderTales was invented as a way of providing feedback to colour-ring readers who focused on Black-tailed Godwits. There are 19 blogs about the species, some of which may well appeal to birdwatchers who have spotted colour-ringed birds anywhere between Belfast Harbour and the Shannon Estuary.

We are all aware that migration is getting earlier but how does this happen? Monitoring the annual arrival of individual colour-ringed Black-tailed Godwits in Iceland may well have provided an answer. Why is spring migration getting earlier? reveals that it is new recruits into the breeding population that are setting the pace; they are reaching Iceland earlier than previous generations.

Another fascinating story that is revealed by colour-ringing is the synchronous arrival in Iceland of the two members of breeding pairs of Black-tailed Godwits, even if one wintered in Ireland and the other in France. You can read more here.

Wintering waders

Ireland is a very important winter destination for Iceland’s Redshank, Golden Plover and Snipe. You can read more in Ireland’s wintering waders, a blog based on the most recent population estimates for the island of Ireland, generated from WeBS data in Northern Ireland and I-WeBS in the Republic. A paper in Irish Birds revealed a 20% drop in wader numbers over a five-year period. One of the biggest declines was in Redshank, most of which will be of Icelandic origin. We don’t really know what is happening to winter numbers of Golden Plover or Snipe.

Greenland and Canada

Each spring, thousands of waders pass through Ireland on their way from Africa to Iceland, and beyond to Greenland and Canada. By the end of the first week of May, most of the waders that breed in Iceland (Black-tailed Godwit, Whimbrel, Redshank, Oystercatcher, Snipe and Golden Plover) will be on territory but birds headed further north are on a later schedule.

The month of May sees departures of Sanderling, Turnstone and Knot that have spent the winter around the coasts of Ireland. Before they go, their numbers will be swelled with the addition of newly-arrived flocks from Africa and southern Europe. The blog Travel advice for Sanderling, reveals fascinating research results about Sanderling migration, generated by thousands of reports of colour-ringed birds. Why do some Sanderling travel all the way from Greenland to South Africa when they could do just as well by staying in Ireland?

Most of these May-departure flocks of waders, which also include Dunlin and Ringed Plover, will stop off in Iceland to refuel and to await good conditions for the next stage of their journeys to the Arctic.

Breeding Waders

WaderTales were developed in East Anglia so many of the articles about breeding waders have an English feel to them. Hopefully, some of the blogs will still appeal. Anyone trying to support breeding Lapwing populations might be interested in A helping hand for Lapwings, which also talks about Redshank. In a more recent blog, Tool-kit for wader conservation, there’s a summary of techniques available to conservationists who focus on waders breeding on lowland wet grassland.

There’s an Icelandic focus to WaderTales too and a blog, which looks at the attitudes of farmers. This may well resonate with conservationists (scientists, birdwatchers and farmers) who are trying to work together to improve conditions for Irish breeding waders. As Icelandic farming expands, what are farmers prepared to do to support breeding waders, many of which are destined to spend the winter on Irish estuaries. See: Do Iceland’s farmers care about wader conservation?

Ireland – a special place for Curlews

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

Is the Curlew really near-threatened? considers the plight of breeding Curlew. It’s easy to understand why BirdWatch Ireland, RSPB, BTO, WWT and GWCT  are focusing on this species How long will it be until breeding Curlew are lost from Ireland, completely?

The threat to the Curlew is real, especially when set in an international context. Two species of curlew are probably already extinct and other members of the Numeniini (curlews, godwits and Upland Sandpiper) are facing a similar set of problems to those that probably caused the demise of the Eskimo Curlew and Slender-billed Curlew. Why are we losing our large waders? outlines the background to a global problem.

There’s a WaderTales blog that summarises a paper from BTO and RSPB – Curlews can’t wait for a treatment plan. Although the analyses are based on British data, the results are highly relevant to Irish Curlews.  If you prefer your Curlew writing to be more lyrical, please read Curlew Moon which has it its heart the similarly titled book by Mary Colwell.

A more recent Curlew blog reveals the results of the Irish breeding survey in the summers of 2015, 2016 & 2017, with the shocking headline figure of a 96% decline: Ireland’s Curlew Crisis.

Conservation issues

Hundreds of  birdwatchers take part in the Irish Wetland Bird Survey (Republic) and the Wetland Bird Survey (Northern Ireland). These counts identify and monitor key sites for wintering waders – and wildfowl. Whilst mud  and sand-flats are, of course, important to waders, so are roost sites. A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. It has been estimated that the cost of flying to and from roosts might account for up to 14% of a bird’s daily energy expenditure. That’s something to think about next time you see a dog chasing off a flock of roosting waders. This blog about Disturbed Turnstone suggests that pressures from people (and dogs) can cause a redistribution of wintering birds.

Further reading

Hopefully, this summary  gives a flavour of some of the issues being faced by Irish waders and the research to which they are contributing. There are already over 90 blogs in the WaderTales series, with one or two new blogs being produced each month. If you want to know how volcanoes affect breeding waders in Iceland, why Black-tailed Godwits wear colour-rings or if there are costs to carrying a geolocator have a look here.

And finally …

There’s a useful summary about wader migration to, from and through Ireland in Which wader, when and why?

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.

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.

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 11^th 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)

The 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

The 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:

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.

One 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.

James, Dan and David refined the summary, bringing it together as a ‘Conservation Statements for Numeniini Species’ which was presented to the 11^th 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.

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.

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.

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:

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  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.

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.

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 41,000 remain, with a decline in the major Canadian population, where there has been reduced nesting & fledging success. The species was added to Canada’s ‘threatened species’ list in 2019 based upon this report from COSEWIC)

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

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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