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

When a flock of Black-tailed Godwit turn 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.

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On 24 February last year, 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.

table & legendRL-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.

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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

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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

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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?

annual colour-ringsThe 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.

air flockThe 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: 1141-1143DOI: 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: 153-158DOI: 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


 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

 

Flyway from Ireland to Iceland

There are thirty WaderTales blogs so far. Here’s a selection of ten that may appeal to birdwatchers in Ireland.

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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.

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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 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 four yellow-ringed Dublin Bay birds in Tiree before the end of February this 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.

snipe-1Each 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.

whimbrel-mig-fig1Some of the last 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.

Black tailed-Godwits

WaderTales was invented as a way of providing feedback to colour-ring readers who focused on Black-tailed Godwits. There are 10 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.

pairs-mapWe 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 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.

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 Redshanks.

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There’s an Icelandic focus too and a new blog, which looks at the attitudes of farmers, will 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

Curlew e (2)

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 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.

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.

Further reading

b-stubble-godwitsHopefully, 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 30 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.


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

Why are we losing our large waders?

A review of the global threats to the world’s Numeniini (curlews, godwits & Upland Sandpiper) has just been published. It 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?

b-curlewThe perilous plight of members of the curlew family 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.
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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.

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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.

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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