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

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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.

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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:

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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.

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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

Do Iceland’s farmers care about wader conservation?

When working with Icelandic farmers to conserve internationally important wader populations, a shared understanding of beneficial practises may be more important than financial incentives.

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Species like Snipe, Redshank and Black-tailed Godwits have been squeezed out of lowland areas of countries such as the UK and the Netherlands by centuries of drainage, increasingly homogeneous landscapes and the introduction of quick-growing grassland monocultures. Adults have lost nesting sites, chicks have fewer feeding opportunities and pre-fledged youngsters fall victim to farm machinery. Do the same fates await waders in Iceland or might it be possible to work with farmers to leave space for birds?

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Pools, set within semi-natural lightly-grazed fields, are important

As part of her PhD at the University of Iceland, in collaboration with the Universities of East Anglia (UK) and Aveiro (Portugal), Lilja Jóhannesdóttir asked farmers what they think about having birds on their land, what their plans are for their farms, whether they might be willing to leave some pools and focus farming activities in areas less important for birds, and if farm subsidies might encourage them to be more proactive conservationists. The sometimes surprising results of this questionnaire have been published in Ecology & Society.

Reconciling biodiversity conservation and agricultural expansion in the subarctic environment of Iceland. Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill  and Tómas G. Gunnarsson. Ecology and Society 22(1):16.

The Waders of Iceland

tableIn a recent report prepared by AEWA (Agreement on the Conservation of African-Eurasian Migratory Waterbirds), in response to concerns about the effects of afforestation on Iceland’s waterbirds, Dave Pritchard & Colin Galbraith say “Iceland is second only to Russia in its importance as a breeding ground for migratory waterbirds in the AEWA region. It supports the most important breeding populations in Europe for six species of waders, and is the second most important country for three.”

Data in the table alongside have been extracted from Annex 4 of their report, which was discussed at the 12th Standing Committee of AEWA in Jan/Feb 2017. Iceland is home to c 75% of Europe’s breeding Whimbrel, over half of the area’s breeding Dunlin and perhaps half of its Golden Plover. The importance of Iceland has increased with the collapse of wader populations in other countries.

Waders on farmland

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Spring flock of Black-tailed Godwit feeding in a stubble field

Farmed landscapes in Iceland provide opportunities for waders. In the spring, newly-arrived flocks of Golden Plover spread out over hayfields, Black-tailed Godwits target the previous year’s barley stubbles and parties of feeding waders can be seen in sedge pools on farms. During the breeding season, the application of fertilisers, especially in areas where volcanic ash deposition is low, increases soil productivity and wader densities, as was shown in this blog about regional productivity. Come the autumn, hayfields attract flocks of birds fattening up for migration. Despite drainage of an estimated 55% to 75% of wetlands in Iceland in the last seventy years, the country is still a great place for waders.

The amount of intensively-farmed land in Iceland is increasing, to some extent driven by rapid recent increases in the number of tourists, who consume milk products and meat. This can be seen in the ongoing development of hayfields, to feed cattle, and barley production, for pig-feed. There is concern that these developments will impact upon wader numbers, through the reduction in the amount of semi-natural habitat, especially in the lowlands, loss of pools and reduced landscape heterogeneity. On top of these changes, warmer temperatures allow earlier cuts of silage which increases the risk of killing wader chicks that nest within these fields.

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More and more semi-natural land is being lost to grass monocultures

Lilja Jóhannesdóttir’s PhD is focused on how birds use the gradient of habitats that comprise farmland in lowland Iceland – from more intensively farmed fields through to lightly-grazed, semi-natural habitats. The paper that forms the focus of this blog looks at farmers’ attitudes to the birds that share Iceland’s farms and their plans for the future. It then attempts to reveal the willingness and capacity of landowners to engage with conservation management practises.

The questionnaire

To understand the views of Icelandic farmers toward bird conservation, given the current potential for agricultural expansion, Lilja interviewed 62 farmers across Iceland, using a structured questionnaire. Some of the key findings are:

  • Over 60% of farmers are likely or very likely to increase their area of cultivated land
  • Over 90% of farmers think it is important or very important to have rich birdlife on their estates
  • About 60% would consider modifying grazing regimes to help birds
  • More than 80% would be unlikely or highly unlikely to consider changing the timing of harvesting operations.
  • More than 80% would be happy to consider keeping pools intact
  • Information on conservation needs are more likely to change attitudes than financial incentives

The information collected in the questionnaires was analysed by region and by the age of the interviewee but no strong patterns emerged. Older farmers seem to appreciate birdlife more than their younger colleagues but are no more likely to change their behaviours to support conservation objectives. The detailed figures are reported in the paper.

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Creating new hayfield to produce cattle-food is at the expense of areas of semi-natural land

The majority of the Icelandic farmers who took part in the survey plan to expand their agricultural land in the next five years, and this is likely to be driven further by increasing demands for farming products. This implies that conversion of semi-natural land into farmland is likely to greatly increase in the near future, with potentially severe and widespread impacts on the internationally important bird populations that currently breed in these areas. Such expansion could put Iceland on a similar trajectory to many other countries that have experienced substantial biodiversity declines on the back of agricultural intensification and expansion. On the positive side, Icelandic farmers like wildlife and the results suggest that if they are better informed about the consequences of their actions they might well try to modify plans in ways that reduce negative impacts. The possibility of financial incentives to off-set potential losses did not seem to influence farmers’ views, but the authors suggest that this might be because there is no tradition for farmers to receive subsidies for conservation action.

b-horsesA clear finding of the study is that farmers are unlikely to change the timing of agricultural operations in order to help birds. Perhaps this is unsurprising in a country with a very short growing season and where periods of settled weather are rare. With relatively few consecutive dry days, opportunities to mow and turn silage or hay crops just have to be taken. The timing of farming operations, such as harvesting/mowing, can be crucial for breeding waders because they can result in the destruction of nests, chicks, and adults during the breeding season. For example, advances in timing of mowing of hayfields in the Netherlands has meant that this now coincides more frequently with wader nesting and chick rearing, causing unsuccessful breeding attempts and leading to lower recruitment. There is more about the Dutch experience in this Ibis paper.

If Icelandic farmers are unlikely to delay operations, perhaps other strategies, such as mowing fields from the centre – as used in the Outer Hebrides to reduce Corncrake losses – might be more acceptable to farmers who are so constrained by the weather? Read more about the Corncrake issue here. 

The Future

b-whimbrelAs a signatory to international agreements on the conservation of birds and wetlands (Ramsar Convention, Bern Convention, Convention on Biological Diversity and African-Eurasian Waterbird Agreement), the Icelandic government is required to take action to protect the internationally important bird populations breeding in the country. Given that there is no strong tradition of using planning laws or centralised agricultural policy to influence farmers’ decisions, working with individual farmers might be the best way to deliver conservation objectives.

Farmers’ views on the importance of having rich birdlife on their land and their willingness to participate in bird conservation provide a potential platform to work with landowners to design conservation management strategies – and to do this before further substantial changes in the extent of agriculture take place in this subarctic landscape. With three-quarters of Europe’s breeding Whimbrel and about half of the Golden Plover and Dunlin dependent upon decisions made in Iceland, there is a lot at stake.

Reconciling biodiversity conservation and agricultural expansion in the subarctic environment of Iceland. Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill  and Tómas G. Gunnarsson. Ecology and Society 22(1):16.

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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

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Black-tailed Godwit pairs – the importance of synchrony

How long does a godwit wait around to see if last year’s mate will turn up?

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Newly-arrived Black-tailed Godwits. Time for a wash & brush up and then off to territory?

Colour-ringing enabled Tómas Gunnarsson to follow the lives of pairs of Black-tailed Godwits nesting near his parents’ home in Iceland. In this world, that is ruled by timing and opportunity, the pairings, divorces and re-pairings could form the plot for a TV soap-opera. The studies turned into a fascinating Nature paper that was written up in The Telegraph newspaper. The two main characters were christened Gretar and Sigga  by the journalist but they’re more commonly known as RY-RO and RO-RO.

A tale of two godwits

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How long should this godwit wait for its mate?

2002: Colour-ringed Black-tailed Godwits RY-RO (red yellow – red orange) and RO-RO bred successfully in Laugaras, in the inland part of Iceland’s Southern Lowlands. Come the autumn, they left Iceland. The female (RO-RO) probably spent the winter in Portugal, although she was only seen there in later years, and the male (RY-RO) opted for the somewhat colder conditions of eastern England.

2003: Next spring, RO-RO arrived on territory on 6 May, before her mate. She cannot have known whether he was late or dead when she made the decision to move in with a new male, who was later colour-ringed as OR-OO.  When RY-RO arrived back a week later, on 13 May, he had to find himself a new female (GG-YO), who had been paired to a different male in 2002.

2004: Come the spring of 2004, RO-RO and RY-RO arrived at the same time and got back together.

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Tómas Gunnarsson with one of the colour-ringed Black-tailed Godwits

This is only one story but it seems to illustrate that there are good reasons to nest with a partner that is well known to you. This could help to illustrate why individual godwits are generally very good at timing their arrival back on territory, to synchronise with their partners, as revealed in this Nature paper, published in 2005.

Gunnarsson, T.G., Gill, J.A., Sigurbjörnsson, Þ. & Sutherland W.J. (2004) Arrival synchrony in migratory birds. Nature, 431, 646-646. DOI: 10.1038/431646a

In the paper the authors described the return of pairs of Icelandic Black-tailed Godwits to Laugaras in the spring of 2003. Godwits generally arrive in Iceland over a one-month period, between mid-April and the middle of May.

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Each line joins the wintering locations of a pair of godwits

On average, previously paired males and females in the study arrived within 3.1 days of one another, despite the fact that males and females from the same pair had spent the winter on average about 1000 km apart and that there is no evidence that any pairs had met at passage sites prior to crossing the Atlantic. Arrival synchrony seems to be related to mate retention, as the only divorces occurred in two of the three pairs that arrived more than eight days apart.

Synchrony in timing of arrival on the breeding grounds may be important for retaining a mate from the previous year and avoiding a costly divorce – but how it is achieved is a mystery.

Warmer springs

Tómas Gunnarsson and his father, Gunnar Tómasson, have been studying the timings of spring arrival in south Iceland of a range of species since 1988. In a 2011 paper in Bird Study they estimated that the timing of arrival of the first black-tailed godwit moved earlier by about 5.5 days per decade over that period. Here’s a link to the paper.

graphAs this advance in spring timing of migration was already happening when Tómas was making observations of the paired birds in Laugaras in 2003, we were all interested to see whether the schedules of marked birds would advance in similar ways. Interestingly, we have been able to show that the timing of arrival of individual Black-tailed Godwits is actually not changing at all. There is year-to-year variation in the dates on which individuals arrive, but no trend. Instead it is new recruits into the population that are driving the earlier migration. There’s a blog about this here.

Whilst there are processes in play that mean new recruits are migrating earlier than their predecessors, there must also be reasons why time-fidelity is important for individual birds. Perhaps synchrony increases the probability that individuals will be able to nest with the same mate in subsequent years? This is hinted at by the fact that godwits have been observed to re-pair with previous partners if opportunities present themselves.

Potential benefits of re-pairing with the same mate

For Black-tailed Godwits, not enough is known about the benefits of retaining the same mate. Given that divorce events are rare, it would be hard to measure any consequences for productivity – even if the nests were easy to find and youngsters easy to track – neither of which is the case. For the moment, all that is available is evidence of divorce and the possibility that females will not wait for males that are late.

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Nests are well hidden

Black-tailed Godwits are long-lived birds, with breeding territories in which resources are generally predictably distributed, and a pair is likely to be familiar with local predator densities and distributions. Whilst one member of the pair is incubating the eggs, the other spends a lot of time looking out for potential predators, and this mutual protection may well confer benefits for the adults and the eggs. Perhaps knowing the behaviour of one’s partner is important during the incubation period?

The complexities of incubating eggs

If the daily routines associated with parental change-overs at the nest become established over time, might this be an important driver towards fidelity? Fast forward to a paper on shorebird incubation patterns, published in Nature in 2016 by Martin Bulla et al, which might provide some clues:

Unexpected diversity in socially synchronised rhythms of shorebirds Nature 540,109–113 (01 December 2016) doi:10.1038/nature20563

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This actogram from the Bulla Nature paper creates some wonderful patterns

This paper is the result of a collaboration between Martin Bulla and 75 of his wader biologist colleagues, all happy to share data on nest incubation patterns which Martin then analysed. This resulted in an amazing data-set of 729 nests from 91 populations of 32 shorebird species, from which Martin was able to report remarkable within- and between-species differences in nest incubation rhythms.

This study suggests that energetic demands are not an important ecological driver of incubation bout length, but instead that pairs have developed idiosyncratic incubation patterns, possibly as an anti-predation strategy. Effectively, risk of predation, rather than risk of starvation, may have a key role in determining some of the variation in incubation rhythms. This means that species that hide their nests (and themselves) incubate for longer and change places less frequently.

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Incubating Ringed Plovers change places frequently

Ringed Plovers, for instance, walk away from their eggs when a potential predator approaches and change places on the nest frequently. A male or female Redshank, on the other hand, will sit tight and brood for about six hours before exchanging with its partner. While partner A is hunkered down on the nest, partner B leaves the area, so as not to draw any attention to the pre-packaged protein that partner A is sitting on. If B is only going to return when A is ready for a surreptitious change-over then the activities of the two need to be well synchronised.

As the authors point out in the paper, although the context for this comparative study was diversity in biparental incubation, it is possible that diverse behavioural rhythms may also arise in other social settings (for example, in the context of mating interactions or vigilance behaviour during group foraging). These are other circumstances in which it may well be beneficial to know one’s partner.

What does this mean for RY-RO and RO-RO?

Perhaps fidelity and synchronicity are really important to Black-tailed Godwits? If only their nests were easier to find and nest success was easier to measure! For the moment, all that we know is that pairs of Icelandic Black-tailed Godwits are remarkably synchronous in their arrival times on breeding territory, and something important must have driven the evolution of such a finely tuned migratory strategy.


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

Dutch Black-tailed Godwit numbers down by nearly 75%

Colour-rings and radio-tracking are helping to chart the ongoing decline of the Dutch Black-tailed Godwit population.

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A Portuguese rice field, full of limosa Black-tailed Godwits; most are Dutch breeders

The Black-tailed Godwit is the national bird of the Netherlands, the country in which the vast majority of the West European limosa race breed. These Dutch birds are an important part of the country’s cultural heritage and are of major international significance. Large amounts of money have gone into supporting the species, and the meadows that they share with others such as Redshank and Snipe, but efforts so far have failed to reverse a Black-tailed Godwit decline that has been going on since at least the 1970s. This negative situation is in stark contrast to the increases seen in the islandica subspecies that breeds in Iceland and winters in countries between Scotland and Spain. (There’s a comparison of the two subspecies in this WaderTales blog)

Counting Black-tailed Godwits

vero-pretty-flockIt is often easier to measure changes in numbers of waders on the wintering grounds, when birds are in flocks, than when pairs are thinly spread across their breeding ranges. For Dutch Black-tailed Godwits, most of which spend the winter in African countries, south and west of the Sahara, however, the best opportunity to monitor population trends occurs in Spain and Portugal in February, when the birds are on their way back to breed.

Each year a small group of ornithologists visit key sites in Extremadura, the Doñana Wetlands and the rice fields of the Tagus Estuary, to count flocks of birds and to look for colour-ringed birds. They’re able to use these counts and sightings of colour-ringed birds to assess what has happened to numbers in the previous twelve months.

grutto-met-ringen-blog

grutto met ringen (ringed Black-tailed Godwit)

In three of the years since 2007 they’ve witnessed increases but in most years the numbers have gone down. As February 2017 approaches, what will this year’s score be? How many of last year’s birds will have died and how many chicks hatched in 2015 and 2016 will be making the migratory journey north for the first time?

When assessing how many breeding godwits there are in the Netherlands the researchers collect and use the following information:

  • Counts of birds seen in flocks in Spain and Portugal.
  • no-legs

    It’s not always easy to see the colour-rings in rice fields

    Counts of colour-ringed birds. There’s a great one-line comment in the newly-published paper that forms the basis of this blog: ‘In total, we checked 420,206 godwits for colour-rings at Spanish and Portuguese staging sites’. That’s a lot of legs – and a huge effort.

  • An assessment of the proportion of islandica Black-tailed godwits in the flocks, so that they can be removed from the estimation process. This proportion had been established previously but were also monitored using sightings of colour-ringed birds of the islandica and limosa subspecies, and by taking account of the proportion of each population that wears rings.
  • ikenveldwerk

    Rosemarie Kentie in the rice fields of the Tagus estuary (Portugal)

    An estimate of the number of the birds that will be flying north to the Netherlands, as opposed to other countries. Limosa Black-tailed Godwits that pass through Iberia are on their way to a range of countries, stretching from the tiny population that breed in the UK, in the Ouse and Nene Washes, across to Germany in the east. This proportion was calculated by monitoring the movements of satellite-tagged individuals.

The results have just been published in a new paper, which also presents annual survival rates, obtained using colour-ring sightings. There is a full explanation of the methodology in the paper. You can also see maps from the satellite-tagging project on the King of the Meadows website.

postEstimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites. Ardea 114: 213–225. doi:10.5253/arde.v104i3.a7

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.

Latest findings

Over the eight years of the survey work, the average decline in numbers of limosa Black-tailed Godwits has been 3.7% per year. Numbers appeared to go up between 2009 and 2011, when the calculated survival rate of young birds was high, but the magnitude of this perceived recovery may have been artificially elevated by an increase in the number of Icelandic birds. From WeBS counts in the United Kingdom, the number of islandica birds is continuing to rise.

Since 2011, the estimated annual decrease has been 6.3% per year. Such large declines can only occur if there is both low recruitment and reduced adult survival.

green-field

Agricultural intensification has seriously affected Dutch Black-tailed Godwits

The estimated breeding population in the Netherlands in 2015 was 33,000 pairs, representing a drop of nearly 75% since 1967. However, the agricultural grasslands of the Netherlands are still the single most important stronghold for breeding limosa  Black-tailed Godwits using the East Atlantic flyway.

The authors finish with a sad conclusion. “Although enormous amounts of money and effort have been expended to conserve continental godwits, our findings make clear that these have been ineffective or insufficient.”

One wonders how much worse the situation would have been without Dutch and European support for Meadow Birds and the ‘King of the Meadows’ in particular?


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Estimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites.  

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.


 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

Black-tailed Godwits and Volcanic Eruptions

Around 360 earthquakes were detected in Iceland in the week beginning 4 December, which is pretty normal. Earthquakes can give hints about impending volcanic eruptions so they’re important to Icelanders –  and, by implication, to Icelandic waders too.

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In the long term, volcanic ash provides the nutrients that improve fertility, as you can read in How volcanic eruptions help waders, but short-term effects can be seriously negative. This was what Tómas Gunnarsson discovered when he went out to count godwit broods at what should have been the height of the 2011 breeding season. He found only two pairs that showed signs of having broods. Was the Grímsvötn eruption between 21 and 28 May to blame?

Assessing producivity

Iceland hosts internationally important breeding populations of several wader species, including almost the entire population of the islandica subspecies of Black-tailed Godwits. For several years, wader biologists in Iceland have been monitoring the breeding performance of Black-tailed Godwits in the Southern Lowlands, by counting pairs with broods along a 198 km transect. Their theory was that breeding performance would be better in warm years because of the advantages of early nesting in warm springs.

graphWith six years of data, a team drawn from the universities of Iceland, Aveiro (Portugal) and East Anglia (UK) have published a paper in the BOU Journal IBIS, which fouses upon the relationship between spring temperature and the number of Black-tailed Godwit broods. In the top graph, taken from the paper, it is clear that there is a lot of variation in productivity, with the lower graph showing a strong association between mean May temperatures and the number of Black-tailed Godwit pairs with chicks. What stands out is  the outlier for 2011, which is excluded from the calculations that produce the regression line. For the five other years R² = 0.94, indicating a very close link between May temperature and productivity, as predicted. Using the mean temperature for May 2011, the number of pairs of godwits with chicks that might have been expected to have been seen in 2011 is about 25 – rather than just two.

The full methods can be viewed in this paper:

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449

The ash effect

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Eyjafjallajokull in 2010

We all remember the eruption of Eyjafjallajökull in 2010. This produced copious amounts of ash, most of which was blown south to mainland Europe, disrupting air travel. Grimsvötn, which erupted in May 2011, was less famous but actually depositied a lot more ash in Iceland, especially in the Southern Lowlands.

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Ash  covered pools and clogged insect traps

On dry days, fieldworkers working in this study area used face masks to protect their respiration, as simply walking through vegetation disturbed large amounts of ash into the air. A layer of ash was frequently observed covering pools in wetlands and traps for invertebrate sampling were often clogged with ash. Short-term negative effects of volcanic dust on birds have been reported previously, probably acting through increased invertebrate mortality, and the low count of successful broods in the warm summer of 2011 seems to bear this out.

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An alarming parent godwit

By monitoring breeding Black-tailed Godwits in southern Iceland, the wader scientists have shown that volcanic activity can have a major impact  on bird productivity. Productivity was back to what appears to be normal (when corrected for mean temperature) by the next summer. The lack of recruitment in 2011 seems to have been reflected in a slight decrease in the counts of Black-tailed Godwits in the United Kingdom in the winter 2011/12 (as measured by WeBS counts), with a resumption in what is generally an upward population trend in 2012/13.

The rapid recovery of productivity in the year following the volcanic eruption (2012) indicates that the negative effects of the incident seem to be have been short in duration. Whimbrels in the same region were also affected by volcanic activity in the summer of the 2011 eruption (Katrínardóttir et al. 2015). In the long-term, the effects of volcanic activity on waders in Iceland are most likely to be positive, as volcanic dust recharges vegetated land with nutrients and buffers pH. Densities of waders across Iceland are generally higher where volcanic dust inputs are higher (Gunnarsson et al. 2015).

singleThis study shows how annual variation in productivity can vary greatly in response to rare and extreme events. As expected for a long-lived species, effects of a single year of very low productivity were short in duration and probably had a limited effect on the population growth rate. The pronounced effect that spring temperature has on annual variation in productivity is likely to be a more significant factor in the future population trajectory of waders, given the ongoing and rapid warming of Arctic and Sub-arctic regions.

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449


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

Overtaking on Migration

When two legs are better than one: the spring migration of Black-tailed Godwits.

headerThe winter range of Icelandic Black-tailed Godwits covers a relatively wide latitudinal spread, from southern Spain to Scotland.  Even though not at the extremes of this distribution, a flock of birds in Lisbon experiences very different mid-winter conditions to a flock of birds in Liverpool.  December days never get shorter than 9hr 27min in Lisbon, which is 2 hours more than in Liverpool, and the average maximum daytime temperature is 14⁰C, as opposed to 6⁰C.  On the negative side, it’s a lot further from Iceland to Portugal than it is to northern England.

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José Alves enjoying warm winter conditions in Portugal

In other studies (of Avocets and Cormorants, for instance) it has been shown that individual birds that winter close to their breeding areas are able to arrive back earlier in the spring than ones that winter further away.  This is not the case in Black-tailed Godwits and this paper, published in Oikos in 2012, explains why.

Overtaking on migration: does longer distance migration always incur a penalty? José A. Alves , Tómas G. Gunnarsson , Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

Background

A team from the universities of East Anglia (UK), Iceland and Aveiro (Portugal) has been monitoring the spring arrival dates of colour-ringed Icelandic Black-tailed Godwits since 2000. The most recent paper to use this data-set has shown that adult birds have remarkably fixed arrival times in Iceland (to within a few days), and that the advancing arrival of the godwit population has been driven by young birds travelling to Iceland for the first time (see wadertales.wordpress.com/2015/11/16/why-is-spring-migration-getting-earlier).  By tracking individual birds and the countries from which they travel, it is clear that the earliest arrivals are actually birds that winter in the southern part of the range – not the birds from northern and central parts of Great Britain, which have about 1500 km less far to travel.

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Black-tailed Godwits on the Tagus estuary (Lisbon)

For birds migrating south from arctic and subarctic breeding grounds, a trade-off might be expected between distance and conditions experienced during winter months. Birds travelling further south are likely to experience much more benign conditions, while those that undertake shorter flights expend less energy and may have the potential to return home earlier or to pick up clues as to the likely conditions they will face on breeding grounds in the early spring.

Work by Tómas Gunnarsson has shown links between arrival of Black-tailed Godwits in Iceland and subsequent breeding success. In areas where most territories are occupied early in the season, over half of pairs fledge youngsters whilst in areas where most territories are occupied later in the spring fewer than half of pairs are successful.  You can read more here.

The easy life in Portugal

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Portuguese rice fields provide alternative feeding opportunities for Black-tailed Godwits

José Alves studied Icelandic Black-tailed Godwits wintering in Portugal as part of his PhD at the University of East Anglia. One of the papers from this work, focusing on energetics and migration strategies, was published in Ecology in 2013:

Costs, benefits, and fitness consequences of different migratory strategies. José A. Alves , Tómas G. Gunnarsson , Daniel B. Hayhow, Graham F. Appleton, Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

energy-figThe paper shows that energetic conditions for wintering godwits are better in Portugal than further north in the winter range

  • Warmer air temperatures and considerably lower wind speeds mean that thermoregulatory costs, and hence energetic requirements, are lower for godwits wintering in west Portugal than in south Ireland or east England.
  • Black-tailed Godwits wintering in Portugal have access to larger numbers of bigger bivalves for the whole winter period. Birds wintering in eastern England or Ireland rarely find these big packages of protein.
  • On average, foraging for c.5 hours per day provides sufficient intake for a Portuguese-wintering Black-tailed Godwit.
  • In Ireland, the food supplies available on mudflats during the daylight hours of a tidal cycle are not sufficient, and godwits also forage on nearby grasslands.
  • In eastern England, rapid depletion of food supplies on estuaries means that resources become very limited in late winter, and are often not sufficient to meet the energy requirements of wintering godwits.

Clearly, Portugal is a great place to spend the winter. It’s just a long way from Iceland.

The Spring Overtake

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The direct route from Portugal to Iceland may be possible but most go via The Netherlands

Portuguese Black-tailed Godwits travel further to their winter site but they break their spring migration into two legs, with most birds moving to the Netherlands in February or March and others staging in France, Great Britain and Ireland. By using Colin Pennycuick’s model ‘Flight’ (Pennycuick, C. J. 2008. Modelling the flying bird. – Academic Press), José Alves and his colleagues investigated the range of spring migration strategies available to individuals, given their body masses. Of Portuguese-wintering Black-tailed Godwits, around 10% are predicted to be able to reach the breeding grounds in one flight. From sightings of colour-ringed birds, it is clear that the vast majority of Portuguese birds do not make direct flights. It is possible that some individuals fly straight to Iceland but no bird has yet been proven to take this option.

When a small number of Black-tailed Godwits were caught in Portugal, just prior to the normal departure time, the masses of individuals were remarkably good predictors of their subsequent movements.

  • The lightest male was predicted to be unable to reach even the first possible stop-over site, in France, and indeed this bird remained in Portugal throughout the breeding season.
  • Of two males with just sufficient mass to reach France, one did indeed get to France and the other remained in Portugal during that breeding season (but did migrate the following year).
  • The remaining seven males were predicted to be able to reach the major stop-over sites in the Netherlands or in east England (both of which are about 1750 km from west Portugal). Thanks to the wonderful network of observers, every one of these birds was spotted in these staging areas. These birds included RO-YGf (below)dutch-bird
  • The only two females caught were both later recorded in the Netherlands; the heavier one was seen shortly after ringing and the lighter one arrived later, possibly having spent time in France.

Black-tailed Godwits are well watched and often deliver day-by-day records. For this species, colour-rings are a cheap and simple technology with which to study migration. You can read more about the network of colour-ring readers in the WaderTales blog, Godwits & Godwiteers.

The Oikos paper goes on to discuss the strategies being employed by Black-tailed Godwits, relating these to the importance of getting to Iceland early. You can read more here:

Overtaking on migration: does longer distance migration always incur a penalty? José A. Alves , Tómas G. Gunnarsson , Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

In Conclusion

Portuguese Black-tailed Godwits make full advantage of benign winter conditions in Portugal and then fly north very early in spring. By moving to the Netherlands (or Britain & Ireland) they are taking up pole position for the race to Iceland.


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

A place to roost

Safe roost sites are important for waders such as Black-tailed Godwits

top-picIt has been said that Black-tailed Godwits are the laziest birds in the world, usually in a frustrated tone while waiting for a marked bird to wake up and reveal the rest of its colour rings. Roosting is not laziness, however; it’s an important resource conservation strategy in the daily balance of energy inputs and outputs.

When Black-tailed Godwits are feeding in tidal systems they have a limited amount of time each day to access the shellfish and worms that make up their diet. These foods are unavailable over the high-tide period, and sometimes in the lull between the ebb and flood, so birds conserve energy by gathering together at roosts. They seek out sites which are safe and sheltered and go to sleep – often for several hours if undisturbed. Theunis Piersma and colleagues have shown that sleep is the most energy efficient form of activity for shorebirds.

In two interesting papers, focusing on Red Knot and Great Knot in Roebuck Bay, North-Western Australia, Danny Rogers and colleagues showed that choice of roost sites seems to involve several criteria:

  • Birds try to find a roost as close as possible to feeding sites, probably to reduce travel costs between feeding areas and high-tide roosts.
  • In particular, birds appear to turn down feeding opportunities that take them further from preferred roost sites.
  • Open roosting sites that provide clear views of any approaching predators seem to be preferred
  • Availability of safe night-time roosts seems to be more restricted, with birds flying further to find a suitable site to wait out the high tide period.
  • The estimated ‘commuting costs’ associated with flying to and from these roosts accounted for between 2% and 8% of daily energy expenditure.
  • Flocks of Knot that were disturbed at roosts and forced to fly around for thirty minutes had an estimated increase in their daily energy expenditure of c 13%.
  • roosting-curlew

    These Curlew, roosting on the shores of the Humber, are minimising energy expenditure in very cold conditions

    Temperatures in Roebuck Bay can frequently exceed 38⁰C, and the waders chose wet sites in which they could keep their feet and legs cool. That’s not a problem for waders wintering in the UK.

The details can be found here:

What does this mean for Black-tailed Godwit in UK conditions?

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Waders often roost in mixed flocks. These birds are resting on an Icelandic beach after crossing the Atlantic

Although the facts, figures and conclusions listed above relate to Red Knot and Great Knot, the authors point out that they gather in mixed roosts with other species to which similar decision-making might apply. The Australian studies took place in very hot conditions but many of the factors influencing roosting site choice are likely to also apply to our cold and wind-swept estuaries in NW Europe. For instance, a study of Knot on the Dee Estuary by Mitchell et al in England estimated that costs of commuting to roosts could account for 14% of daily energy expenditure.

energy-figEnergetic constraints are likely to present different issues for arctic waders that spend the non-breeding season in the northern hemisphere than for ones that choose to cross the equator, and experience warmer conditions and heat stress. Even within Europe, the energetic balances that waders can experience on different estuaries can vary widely. In their 2013 Ecology paper on Black-tailed Godwit energetics, Costs, benefits, and fitness consequences of different migratory strategies  José Alves and colleagues showed that mild weather and abundant food supplies result in a positive energy balance for godwits wintering on the Tagus estuary in Portugal and, to a lesser extent, the estuaries of south Ireland. In east England estuaries, however, the costs of keeping warm can sometimes exceed the energy available from the food supplies (see figure). In such circumstances, an undisturbed roost, located as close as possible to feeding areas may well be especially important.

Consequences of roost loss

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Colour-marked Redshank demonstrated the individual consequences of habitat loss

Although it is very hard to demonstrate population-level consequences of removing roosting sites, we have some clues about the how birds respond to removal of roosts and foraging sites from impact assessment work carried out by the BTO on Redshank in the Cardiff Bay area. When this bay was closed and flooded for commercial development, Redshanks lost both feeding areas and traditional roosting sites. Tracking of colour-ringed Redshanks showed that displaced birds moved to new feeding areas and roost sites up to 19 km away, but mostly stayed close-by on the mudflats of the River Rhymney. Cannon-net catches of these flocks provided measurements of bird mass before and after the closure of the Bay, which revealed that adult Redshank from the Bay had difficulty in maintaining body condition in the first winter following closure and that their survival rates in subsequent winters remained lower than birds that had previously been settled in the Rhymney area. Three papers are essential reading for anyone interested in the consequences of displacements caused by development projects.

ynrx-for-blogA key point of both the Knot work in Australia and the Redshank impact assessment study in Wales is the energetic costs to individuals that can result from the disruption caused by the loss of roosting or foraging sites. Indeed, individual waders may even have favoured locations within roosts that they consistently use. For example, at Gilroy Nature Park, a shallow pool where up to 3500 of the Black-tailed Godwits that feed on the Dee estuary in NW England regularly gather to roost, observers of colour-ringed birds have noticed that marked individual godwits (eg YN-RX pictured here) are often seen in exactly the same place within the pool and flock.  Losing a roosting site of which individuals have such detailed knowledge, and forcing flocks of birds to find alternative roosting locations, may therefore have bigger consequences than just the kilometres covered.

Importance of individual sites

mapThe total number of Icelandic Black-tailed godwits was estimated to be 47,000 in 2004, a figure that is likely to be closer to 60,000 now as the population has continued to grow. This means that a flock of 3,000 birds represents about 5% of the total of the entire breeding population. There is a small number of sites across the United Kingdom that hold these sorts of numbers at different stages of the year. According to the latest figures from the Wetland Bird Survey, numbers on the Wash and Humber estuaries in east England peak at averages of 8198 and 3413 in September, there are 4339 Black-tailed Godwits on the Welsh side of the Dee estuary in October and 5909 on the English side in November. The mean count on the Thames also peaks in November (5883). As the winter progresses, numbers on the nearby Ribble estuary rise to a mean of 4234 in January, there is a mean maximum of 3236 on the Washes in February and 3191 on the Blackwater in March. Although all of these sites are important to Icelandic Black-tailed Godwits throughout the non-breeding period, the different timing of peak counts illustrates the reliance of Icelandic birds on a network of sites. To get a feel for the range of strategies used by individual birds, see Godwits and Godwiteers.

Conservation

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Roosting Black-tailed  Godwits at Gilroy Nature Reserve share their pool with a horse and Canada Geese

While estuarine feeding areas across Europe are well safeguarded, through the network of Special Protection Areas, roost sites are not always as well served, especially if birds spend the high tide period on sites outside the SPA boundary of their foraging areas, such as the freshwater pool at Gilroy Nature Reserve, inland of the Dee Estuary. Some roost sites such as North Killingholme Haven Pits on the Humber have been included within a designated SPA formed by the adjacent mudflats but others, such as Gilroy, are discrete sites outside the SPA. Maintaining the wader populations that forage on our estuarine mudflats may depend upon our capacity to protect their safe roosting sites, even if they are not currently designated.


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

Godwits in, Godwits out: springtime on the Washes

It’s all change in the East Anglian Washes in April, as a small number of limosa Black-tailed Godwits return to breed while thousands of islandica godwits are preparing to depart.

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Black-tailed Godwits land in front of the main hide at WWT Welney (Graham Catley)

The Ouse and Nene Washes in Norfolk and Cambridgeshire are designated as Special Protection Areas (SPAs) under the European Birds Directive, in large part because of their breeding and wintering wader populations. Although the primary reason for their esixtence is to store water that falls as heavy rain further inland, and to thus prevent the flooding of  arable farmland, this periodic inundation has created areas that are relatively free of development and hence great nature sites.  There are no buildings and farming is largely restricted to seasonal grazing, much of which is tailored to provide appropriate feeding areas for wader chicks in the summer and ducks in the winter.

Limosa godwits

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GW-WB was ringed as a chick on the Nene Washes in 2001 and turned up at Cley, on the Norfolk coast, in June/July of six summers between 2005 and 2013  (Pat Wileman)

Typically, only about 40 pairs of limosa Black-tailed Godwits attempt to breed on the Nene Washes each year and 2 to 4 pairs on the Ouse Washes.  Productivity can be low, despite positive habitat management, with summer flooding accounting for frequent losses on the Ouse Washes, while predation has become a recent issue affecting productivity on the Nene Washes.

Problems for breeding limosa are not restricted to England. This is a race that is in trouble, especially in the Netherlands, where the Black-tailed Godwit is the national bird. Attempts have been made to adapt grassland management during the breeding season and to restrict autumn hunting in France but numbers are still declining. There could also be problems with declining area and quality of wetlands in West Africa, where these birds spend the middle part of the winter.

Many chicks from the Nene Washes were colour-ringed by RSPB scientists between 1999 and 2003. We know that some of these birds turned up at coastal sites in England in the early autumn before joining birds from continental Europe as they travelled south through France, Spain and Portugal and on to countries such as Mauretania and Guinea Bissau in western Africa.

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YR-RE feeding with a Dutch-ringed limosa in Senegal (Bram Piot)

A new colour-ring scheme started in 2015, which also involves marking breeding adults. It produced the first colour-ring observation of a Nene-breeding Black-tailed Godwit in Africa. YR-RE (Yellow Red – Red E-Lime) was spotted feeding near Dakar, Senegal on 3rd and 4th January 2016. She was seen again on a Portuguese rice-field on 2nd February 2016. When she returns to the Nene Washes of Cambridgeshire she will find lots of islandica already in residence.

Limosa or Islandica?

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The forehead is more prominent in islandica (Pat Wileman)

It is not easy to distinguish between the two races of Black-tailed Godwits, unless there are marked individuals wearing colour-rings. Even in breeding plumage the differences are subtle. Some male islandica are small and dark but there is much variation across the subspecies. Head shape may be helpful. In the pictures alongside, the bill of the limosa seems to be a smooth extension of the head and there is much less of a distinct forehead than in an islandica. Body size and shape measurements may assist researchers but birds can still be misidentified in the hand. Occasional birds that have been satellite-tagged as limosa in Portugal or Spain end up migrating to Iceland instead of the Netherlands.

Islandica godwits

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G -GO/W was one of the Stour birds that visited Welney (Ed Keeble)

The Washes have not been managed for Icelandic Black-tailed Godwits and their use of the site in the winter is a relatively new phenomenon. These days a flock can appear at the WWT Welney Reserve as early as November and there will almost certainly be some birds to see on the reserve or on nearby washes, unless water levels are very high. Many of these godwits will have previously moulted close by, on the Wash & Humber, but others will join them from the Suffolk and Essex estuaries. When Jenny Gill and I visited the site on 30 December 2015 there had been a recent influx of birds and we identified 42 colour-ringed individuals from east coast estuaries. In January 2016, following heavy rainfall that flooded the Washes, there was a sudden influx of hundreds of extra godwits to the Stour estuary in Essex, that included several that we had seen at Welney in December.

As February turns to March and then April, more new birds join the flocks feeding along the water’s edge in the flooded washes. The appearance of birds wearing orange flags and green flags signals the arrival of individuals from France and Portugal. Although most birds that winter in continental Europe prepare for the last leg of their journeys to Iceland in The Netherlands others choose to fatten up in eastern England.

Use of the Nene Washes is less predictable than the Ouse Washes but large flocks can be found during late March and April. In some springs, four-figure flocks feed on the RSPB reserve at Welches Dam on the Ouse but in others, such as in 2016, the water levels are too high and birds appear on the Nene Washes at Eldernell and further west towards Peterborough on the Low Washes.

Conservation importance for islandica

flock in air

Graham Catley

Every time a birdwatcher reports a flock of 1000 islandica Black-tailed Godwits, she or he is looking at around 2% of the whole Icelandic population, which now likely numbers around 60,000 birds. One of the largest single flocks that has been reported in the area was 4000 on the Nene Washes on 9 March 2008, which must have been about 15% of the Icelandic population at that time. This is an amazingly large part of any wader population to be seen in one place and emphasises the tremendous importance of the Nene and Ouse Washes. Fortunately, much of the land in these areas is farmed in such a way as to provide great breeding and wintering conditions for ground-nesting birds. The only problems occur when prolonged flooding means that these resources are not available to birds preparing for the flight to Iceland

New hope for limosa breeding in the Ouse & Nene Washes

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Nene Washes RSPB reserve (RSPB)

These are exciting times for limosa godwits in the UK. The RSPB, in partnership with WWT, have attracted European funding for a five-year recovery project for these birds. Securing the future of the Nene-breeding godwits is central to this project, through increasing the area of suitable breeding habitat and improving predator management, alongside research to assess the success of these actions. Having only one really key breeding area always leaves a population vulnerable, so re-establishing more breeding populations on the newly created wet grasslands adjacent to the Ouse Washes is also critical to the future of Black-tailed Godwits, as a breeding species in the UK.


 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