Sixty years of Wash waders

wwrg tt balance

Weighing a Turnstone

The Wash Wader Ringing Group (WWRG) started with a bang on 18 August 1959, when the team made a catch of 1,132 birds in a Wildfowl Trust rocket-net at Terrington, in Norfolk. Over the years, cannon have replaced rockets, catches have become generally smaller and the scientific priorities have been refined, but the Group continues to focus upon discovering more about the waders that use the Wash. This blog attempts to summarises what has been learnt about the waders that rely upon the Wash, the vast muddy estuary that lies between Lincolnshire and Norfolk, on the east coast of England.

Sixty years ago, the first goal was to understand where the vast flocks of waders that visit the Wash came from – a task that would provide great insights into the way that the whole East Atlantic Flyway works. In this time, over 300,000 birds have been caught and ringed on the Wash, as you can see in the table below. Equally importantly, hundreds of bird-ringers from across the UK and scores of visitors from around the world have joined WWRG teams, in order to learn more about the study of shorebirds. Further international collaboration has been fostered through overseas visits by WWRG members and emigration of some key personnel. The impact of the Group is truly global, as you can read in the WWRG report for 2014/2015.

wwrg table

A total of 307,226 birds is impressive, especially when some of the species totals are compared to the national totals of the BTO Ringing Scheme for the whole of Britain & Ireland since 1909. WWRG is responsible for over 40% of the Grey Plover, Knot, Sanderling and Bar-tailed Godwit, with Grey Plover topping the list at nearly 60%. These are terrific achievements for a group of volunteers. I don’t have the figures but I reckon that Nigel Clark has been responsible for the largest number of catches.

Wee quiz: What’s the best match between these Wash waders and the countries that they are quite likely to have come from? Answers at the end of the blog:

  • Species: Bar-tailed Godwit, Black-tailed Godwit, Curlew, Oystercatcher, Sanderling, Turnstone
  • Countries: Canada, Greenland, Iceland, Norway, Finland & Russia
wwrg box

Firing box connected to 4 cannon-nets

In the early days, rocket nets were borrowed from the Wildfowl Trust for an annual summer week of catches, but the development of cannon-nets gave opportunities for all-year ringing. The intensity of the Group’s activities grew in the 1970s, when there was a threat to build a freshwater reservoir on the mudflats. For a couple of years, Clive Minton (founder and leader) persuaded us to visit fortnightly, so that we could get better data on weight-gain and turn-over, using a mixture of cannon-netting and mist-netting. Everything we knew was published by the Group as The Wash Feasibility Study in 1975. These days, the Group gets together about ten times a year for catching and colour-ring-reading sessions.

wwrg oldies

By catching and ringing large numbers of the key species that visit the Wash, the Group was able to generate maps showing what are now well-known patterns of migration (see Which wader, when and why?). Early on in the Group’s history, there was a focus on nine species, with Black-tailed Godwit added as a tenth when numbers increased. Each of these species has its own section below. The maps were prepared for the Wash Wader Ringing Group 2016/2017 Report by Ryan Burrell, using data stored within the BTO archives. Blue dots represent WWRG-ringed birds that have been found abroad. Red triangles represent foreign-ringed birds caught on the Wash. The base maps used are by courtesy of Natural Earth (www.naturalearthdata.com).

Oystercatcher

wwrg map OCThe map alongside clearly demonstrates the strong link between the Wash and Norway. Other interesting things that have been discovered about Oystercatchers:

  • They live a long time. An Oystercatcher that we caught at Friskney on 30 July 1976 broke the longevity record for a BTO-ringed wader when it was shot in France on 4 April 2017 (41 years 1 month and 5 days). It was ringed as an adult so we don’t know the exact age – but it must have been at least 43 years old. There’s a WaderTales blog with a list of longevity records for BTO-ringed waders.
  • When life gets tough, Oystercatchers fail to complete their autumn moult, retaining some of their outer primaries for an extra year. The ability to complete moult and annual survival rates are both affected by cockle and mussel supplies on the Wash. There’s more about this in two papers in Biological Conservation and the Journal of Applied Ecology.

Grey Plover

wwrg GV GVIn the early days of the WWRG, Grey Plovers occurred in much smaller numbers than they do now. Writing in an article about the first 40 years of the Group, Clive Minton told the story of the first catch of 100, made in 1963, that was celebrated with three bottles of champagne provided by the late Hugh Boyd, delivering on an incentive that he had promised.

  • Over half of the Grey Plover that have been ringed in Britain & Ireland since 1909 have been ringed by WWRG since 1959 (58.9%)
  • All of the Grey Plover using the Wash breed in Siberia. Some birds spend the winter on the Wash but there are autumn moulting flocks of birds that will go on to winter in other parts of Britain & Ireland, and spring and autumn passage of birds that travel as far south as West Africa.
  • Grey Plover are late to leave the Wash, with the last departures not occurring until the start of June. Unsurprisingly, they are some of the last waders to return at the end of summer, which puts pressure on birds to finish moult before the short, cold days of winter. Some adults fail to complete primary moult, especially if food supplies are low. There is more about Grey Plover moult in this WaderTales blog.

wwrg map GV KN

Knot

wash knot

First-winter Knot (subterminal bands on wing coverts and, as yet, unmoulted juvenile fethers on upper-parts)

Knot (or Red Knot) are truly international waders, as is shown in this map of movements of islandica  (and a few canutus) birds  to and from the Wash. Several WWRG members have been heavily involved in efforts to understand the decline in numbers of the rufa subspecies in Delaware Bay (on the North American eastern seaboard) and Clive Minton has been at the heart of efforts to explain the sudden drop in survival of piersmai and rogersi adults that winter in Australia and migrate to Arctic Russia via the Yellow Sea (see Wader declines in the shrinking Yellow Sea).

  • We are still learning about Knot migration. The cluster of reports of WWRG-ringed birds in Northern Norway looks odd on this map projection but it turns out that this is a well-used stopping-off point for islandica Knot heading for northern Greenland and NE Canada. This route was first confirmed in 1985, when a joint Durham University and Tromsø University expedition caught 18 Wash-ringed birds in a total catch of 1703 birds.
  • wwrg net set

    Setting cannon-nets

    Many birdwatchers visit the Wash in autumn and winter to see the swirling Knot flocks at Snettisham and Holme. If high tide is at first light, Knot and other waders sometimes roost on Heacham Beach, giving the occasional opportunity to make a significant catch. The most recent of these, on 11 February in 2012, included 2757 Knot, 77 of which were already wearing rings.

  • The most recent analysis of wader populations in Great Britain showed that there was a drop of nearly 20% in wintering Knot numbers (from 320k to 260k) in less than a decade (see Do population estimates matter?). Regular catches on the Wash will help produce estimates of annual survival rates and age ratios of the islandica subspecies.

Sanderling

wwrg sanderlingThe biggest catches of Sanderling are generally in the summer, when the Wash is a meeting point for birds from Greenland and Siberia. July can sometimes see catches of 200 or more birds. Traditionally, a Sanderling catch was the curtain-raiser at the start of Wash Week, an opportunity for the whole team to make one catch before splitting into ‘Terrington’ and ‘Lincolnshire’ teams for the rest of the main summer trip.

  • Wintering Sanderling on the Wash are thought to be exclusively of the race that heads northwest in the spring, to Greenland via Iceland.
  • Late summer and spring see the addition of birds passing through on their way from/to Siberian and Greenlandic breeding areas.
  • I well remember the first time we caught a Sanderling (on 26 July 1975) wearing an Italian ring (caught in Italy 9 May 1975). Thanks to Jeroen Reneerkens (whose work will be covered in an upcoming blog) I now understand that this is probably a bird that migrates from Namibia to Greenland in spring, via the Mediterranean. It will have been on its way back to Namibia when caught in July.

wwrg map SS DN

Dunlin

wash dunlin

Sam Franks, looking for the buffy tips on inner coverts, which distinguish first-year birds from adults

Nearly half of the waders caught by WWRG have been Dunlin – a total of 140,168 up until the end of 2018. There were really big flocks of Dunlin in the 1970s but numbers have dropped over the years, with peak counts now half what they were, according to WeBS data.

  • We caught over 3,500 Dunlin in one week in 1976 but the annual total has exceeded 1,000 in only four of the last ten years. Partly, this reflects a change in behaviour in the summertime, with fewer waders roosting on fields and hence less catchable.
  • Three races of Dunlin visit the UK. Our winter birds are alpina, from Siberia, NW Russia and northern Scandinavia. A lot of July birds are schinzii, breeding in the UK and as far north as Greenland, and we occasionally try to convince ourselves that we have caught an arctica from northern Greenland.
  • Data collected for the WeBS survey suggest that national winter totals have dropped by over 40% in 25 years. This could perhaps partly be explained by a redistribution of alpina, with new generations of young birds settling in wintering areas on the other side of the North Sea. Warmer winters may well make this a more practical proposition than in the 1970s. There’s more about this in this paper.

Black-tailed Godwit

wash blackwit

Newly ringed Black-tailed Godwit, caught in a mist-net at night.

Black-tailed Godwits became a priority species in 1995, when Jennifer Gill (University of East Anglia) started a project to study the movements of individuals, using colour-rings. Nearly 25 years later, the WWRG-ringed Black-tailed Godwits have contributed data to numerous papers, largely focusing upon migration.

  • The Wash is a hugely important area for moulting islandica Black-tailed Godwits. Some birds stay in East Anglia for the winter but others move south and west within the UK, west to Ireland and south to France, Portugal and Spain.
  • There are several blogs about Black-tailed Godwits in this WaderTales contents list.

Bar-tailed Godwit

One of the key things that was learned from the sudden decline in annual survival rates in a range of species that use the Yellow Sea (as mentioned above) is a need for regular monitoring of marked birds. The WWRG’s Scientific Committee set up colour-flagging projects for Bar-tailed Godwit, Curlew and Grey Plover, in order to increase the reliability of estimates of annual survival for three species that the Group does not catch in sufficient numbers to generate good retrap histories. Birdwatchers can help by reporting colour-marked birds here.

wwrg barwit map etc

  • In Bar-tailed Godwits: Migration & Survival there is a comparison of the data generated by a catch of 505 Bar-tailed Godwits in 1976 with the information that has been generated recently, using colour-flags.
  • Bar-tailed Godwits are long-lived birds. A WWRG bird holds the current record for a BTO-ringed Bar-tailed Godwit: 33 years and 11 months between ringing in 1978 and recapture in 2008. BTO longevity records are discussed in this WaderTales blog.
  • Colour-ring reading is now a significant element of Group activities, as described by Rob Pell in the WWRG Report for 2016/2017.

Curlew

Back in the 1970s, Curlew were still hunted on the Wash (paté made from autumn-shot birds was reported to be very tasty). Shooting stopped in Great Britain in 1981, when the maximum winter count on the Wash had dropped to about 3,000 birds, and by 2003/04 the maximum winter count was 15,336. Since then, numbers have declined, in line with national and international trends.

wwrg curlew map etc

  • A large number of Curlew on the Wash in winter are from Finland and surrounding countries. Surprisingly few are of UK origin.
  • Birds wearing WWRG leg-flags have been observed breeding in the Brecks (Norfolk/Suffolk).
  • The Curlew is internationally designated as ‘Near Threatened’. Is this really true when we can still see a field with 1000 roosting Curlew in Norfolk? Answers here.

Redshank

wash redshThe latest population estimates suggest that Great Britain has lost 26,000 wintering Redshank in less than a decade, representing a drop of 20%. Perhaps WWRG data can be used to help to explain these declines? Here are some of the things we know:

  • The Redshank on The Wash in the winter are mainly a mixture of birds from around the Wash, across the UK and from Iceland.
  • In cold winters, Redshank wintering on the Wash die in large numbers. After a period of severe weather in 1991, nearly 3,000 wader corpses were collected from along the tide-line, about 50% of which were Redshank. The winter WeBS counts for Redshank dropped by 50% after this mortality event but have recovered somewhat since then.
  • An analysis of nearly 1,000 dead Redshank showed that about two-thirds were of Icelandic origin. There was a tendency for smaller birds to be more susceptible to cold weather mortality than larger birds of the same species (More information in this paper by Jacquie Clark)

wwrg map RK TT

Turnstone

wash ttWinter Turnstone are birds that will head for Greenland and NE Canada in the spring but recoveries of birds in Finland and other Scandinavian countries indicate a passage of continental birds. African recoveries of WWRG-ringed birds probably include birds from Canada/Greenland and Finland/Scandinavia.

  • Turnstone wearing US Fish & Wildlife Service rings are occasionally caught on the Wash. Some of these rings were put on by Guy Morrison and his colleagues in Alert, Ellesmere Island, Canada. Guy was an early member of WWRG. It’s a small world!
  • The first Wash Turnstone were colour-ringed in 1999, as part of a study to understand why birds were feeding on the docks at Sutton Bridge. There is a WaderTales blog about the resulting paper by Jen Smart and Jennifer Gill. Colour-ringing continues, to measure annual survival rates.
  • Turnstone have a reputation for eating almost anything (including dog excrement and a human corpse) so do not be surprised if you see a colour-ringed bird scavenging for chips on the Hunstanton sea-front.

A few more highlights

Ringed Plover: this is not one of the ten key study species but 1,432 have been ringed between 1959 and 2018. Some birds are local breeders that hardly move anywhere but other birds link the Wash with Greenland, northern Norway, Morocco and Senegal.

wwrg GKGreenshank: The Group supports a colour-ringing project that was initiated by Pete Potts, in Hampshire. More information here.

Spotted Redshank: During the period 1959 to 2018, WWRG ringed a total of 85 Spotted Redshank, representing over 20% of the total ringed in Britain and Ireland since 1909. Amazingly, sixty of these birds were ringed on the same day – 27 July 1975. There is a blog about this catch and the recent decline in the number of Spotted Redshank visiting the UK. Fewer Spotted Redshanks.

Ruff: Until its closure, WWRG members spent many a smelly night at Wisbech Sewage Farm. This was a great place to catch Ruff, Curlew Sandpipers, Green Sandpipers etc. in mist-nets. Group members wrote a paper about Ruff moult and migration.

Rares: Occasionally there are surprises! WWRG has caught one each of Stone Curlew, Pectoral Sandpiper, Broad-billed Sandpiper and Terek Sandpiper. The last bird features in this WWRG blog.

What do we know now?

Migration studies have revealed the importance of the Wash to half a million or more waders each year – birds that spend the whole winter, others that refuel in the spring and vast numbers that rely on the food supplies in the mud to provide the energy for the post-breeding moult. There’s a selection of papers that have included WWRG data here, on the Group’s web-site.

wwrg cr TTThe Group still aims to maintain its general ringing programme, so that a representative sample of the key species carry rings. Colour-ringing projects aim to provide survival estimates for Curlew, Bar-tailed Godwit, Grey Plover and Turnstone, with Greenshank and Black-tailed Godwit colour-rings contributing to migration studies. Birdwatchers who visit the Wash can help by reporting colour-marked birds here, on the WWRG web-site.

WWRG data have been used to help inform decisions about the future of the Wash but the threats keep coming. Studies of migration and seasonal turn-over in numbers contributed hugely to decisions to provide national and international protection to the area and to fend off the 1970s plan to build a freshwater reservoir on the rich mudflats. The information that has been generated by many generations of volunteers over a period of sixty years has been used to manage the level of shellfish exploitation, to inform decisions about wind turbine locations and to manage activities that can cause disturbance.

The Wash Wader Ringing Group is very keen for its data to be used – and not just for impact assessment studies. Click here to learn more.

Diamond Jubilee

PLI

Phil Ireland releasing a Curlew

Over one thousand people are estimated to have contributed to sixty years of the Wash Wader Ringing Group’s activities. We have lived in barns, rolled cars, dug tens of thousands of holes, carried nets for miles, made important catches, had depressing failures, got frostbite, been threatened by surge tides and made friends for life.

In the whole of this period, there have been only two leaders of the Group – Clive Minton (1959-1981) and Phil Ireland (1981-present). Bird ringers, wader biologists and millions of waders owe them both a huge debt of gratitude.

You can read more about the history of WWRG on the Group’s website:

wwrg sunset

Photo at the top of this blog is by Cathy Ryden. Many thanks to her and to other photographers.

Wee quiz:

  • Bar-tailed Godwit – Russia
  • Black-tailed Godwit – Iceland
  • Curlew – Finland
  • Oystercatcher – Norway
  • Sanderling – Greenland
  • Turnstone – Canada

 


GFA in Iceland

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

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Generational change

blog TGG on postIn a changing world, with more chaotic weather patterns and rapidly altering habitats, migratory birds are faced with opportunities and challenges. Long-term monitoring of colour-ringed Black-tailed Godwits, during a period of range expansion and phenological change, has revealed that individuals behave consistently over time but that the behaviour of new generations is moulded by the conditions they encounter.

A changing world 

When trying to explain observed changes in the distributions and annual cycles of migratory birds, there are many things to consider:

  • blog VM y flag

    Colour-rings enable life-time tracking. This bird, caught on its nest, had been ringed as a chick.

    Are individual birds able to take advantage of new breeding and non-breeding sites, as they become available, particularly if other areas become less suitable?

  • Are individuals able to change the timings and patterns of migration?
  • Do individuals adjust their migration routes as a consequence of changes in stop-over or wintering areas?
  • If individuals do not change what they do, how do we explain range expansions and changes in timing of migration?

Put simply, how does climate change lead to changes in distribution of migratory birds? Answering this question is key to being able to predict the rate and direction of future changes, and to assess whether our existing networks of protected sites will continue to support populations in the way that was intended. This issue was tackled by Jennifer Gill, José Alves and Tómas Gunnarsson in their paper “Mechanisms driving phenological and range change in migratory species”, published in Linking behaviour to dynamics of population and communities: applications of novel approaches in behavioural ecology and conservation, a special issue of Philosophical Transactions B (Royal Society).

Potential models

Change could happen in two main ways:

  • Individuals could relocate – having knowledge of a range of available conditions, they can choose to move elsewhere.
  • New generations could settle in new areas (in the breeding season, the non-breeding season or both) and/or adopt new migratory strategies.
blog map

Map that illustrates range expansion

Working out whether change happens through individual movement or generational shifts can only be done by life-long tracking of individuals, in populations in which range change is happening. The Icelandic population of Black-tailed Godwit is ideal for such an investigation. Black-tailed Godwits have been expanding into new breeding areas of Iceland for over 100 years, as discussed in this WaderTales blog. Population growth has been facilitated through warming spring conditions, as discussed in From local warming to range expansion.

blog TGG juvs

Naive youngsters, gathering together before migration

Icelandic Black-tailed Godwits fly south in the autumn, to spend the winter in the British Isles, The Netherlands, Belgium, France, Spain and Portugal. As numbers have grown, winter counts have increased in many areas, with new flocks appearing and expanding on estuaries and areas of wet grassland where the species was previously absent or scarce.

 

Winter distribution

The Wetland Bird Survey shows that there are three times as many Black-tailed Godwits wintering in Great Britain as there were 25 years ago. The biggest changes in numbers have occurred on estuaries in the northwest of England, with the Morecambe Bay winter maximum rising from about 180 to 3200, for instance. Where have these extra birds come from?

blog juvs on Axe

These young birds happen to have ended up on the Axe Estuary in Somerset

Black-tailed Godwits have been ringed in Iceland for nearly twenty years, providing a pool of known-age adults for which natal sites are known. Winter observations of colour-ringed individuals have shown an interesting pattern; birds breeding in newly-colonised areas, particularly in north and east Iceland, are the ones that are more likely to be found in newer winter sites.

In their paper, the authors suggest that birds nesting in these colder areas, where spring comes later, will be fledging quite late and leaving Iceland after adults have departed. With no experienced birds to follow, these young birds may well stop off at the first suitable site, many of which are in the north of the wintering range, and then they return to breed in their natal sites. Birds in Morecambe Bay don’t know that days are longer and the weather is kinder for other birds that travel further south to wintering areas such as Portugal.

blog RS Dee

Wintering birds in Northwest England

Observations from birdwatchers show that the same colour-ringed individuals are nearly always found at the same wintering sites each year. Whatever mechanism is producing this new-breeding-site to new-wintering-site link, it is becoming clear that older birds continue to do what they have always done, with changes in distribution happening as a result of a generational shift.

The annual cycle

Colour-ringed Black-tailed Godwits have been tracked for over 25 years, with a small number of individuals contributing data for the whole of this period. This tracking information can be used to ask how much individuals move around and experience different sites and to assess whether individuals from different generations are using different parts of the range.

Using colour-rings, the Black-tailed Godwit team has discovered that, although individuals can live for over 20 years, in that time they generally use a total of only about four sites between leaving Iceland in late summer and returning in the spring. Basically, individual birds have very limited experience of sites and there is no evidence that they have moved to occupy different sites as, for instance, winter conditions have changed.

blog infographic

Spring arrivals in Iceland

Colour-ring observations have shown that individual birds do not change their breeding or wintering locations and that migrating individuals often appear in the same stop-over sites year after year. The timing of movements is also pretty consistent, especially in the spring. A previous WaderTales blog called Why is spring migration getting earlier? demonstrated that the timing of  migration of individual Black-tailed Godwits varies very little, with observed shifts in the period of migration being driven by young birds returning to Iceland for the first time on average doing so somewhat earlier than previous generations. Once individual birds settle into a timing pattern, they stick to it.

blog LJ arrivals

Black-tailed Godwits, newly arrived in Iceland after crossing the Atlantic

Migration patterns

As discussed above, individual Icelandic Black-tailed Godwits have experience of only a small number of sites, which they use on an annual cycle. When migrating, a bird will generally use the same stop-over site when breaking its journey south, to undertake autumn moult, or on their way north, to take on fat for the trans-Atlantic journey. There is a range of spring migratory strategies in islandica Black-tailed Godwits, as discussed in Overtaking on migration.

blog wwrwOnce established, the annual migratory programmes of individuals rarely change, as illustrated by the map to the right. Colour-ringed Black-tailed Godwit W-WR/W regularly moulted on the Wash, in eastern England, before spending the late winter and spring in northwest England. In the late summer of 2002 he was reported at Slimbridge on 18th and 20th July but back on the Wash on the 25th. Having made the Atlantic crossing and ended up in southwest England, he was able to correct what he may have perceived to be his mistake, returning to the moulting area that he had been using since at least 1996.

Individuals might not change their annual migration routes but we do see changes in numbers on different sites that are used during migratory stop-overs. In a paper published in 2018, Mo Verhoeven and colleagues investigated whether observed changes in migratory patterns of a population of the limosa subspecies of Black-tailed Godwit were caused by individuals altering their strategies or by generational change.

Limosa Black-tailed Godwits leave breeding areas in countries such as The Netherlands in late summer, heading south to either West Africa or Iberia, where they spend the winter. In spring they all gather in staging sites in Portugal and Spain, typically on rice fields. Over the course of less than ten years, the average peak number in Extremadura (Spain) has dropped from about 24,000 to 10,000, while the numbers on the Tagus and Sado estuaries rose from 44,000 to 51,000. These changes took place during a period of rapid population decline, as described in this blog focusing on a paper by Rosemarie Kentie and colleagues.

blog VM Tagus

Limosa Black-tailed Godwits feeding in a rice field in the Tagus estuary

Mo Verhoeven et al have shown that this rapid population-level shift in spring stop-over sites from Spain to Portugal, 300 km further west, was driven by young godwits increasingly using Portugal in the period January to March, instead of Spain. Nearly all of the older birds stuck with the routes they knew. The paper is Generational shift in spring staging site use by a long-distance migratory bird.

Change happens to birds

One thing that is becoming clear in Black-tailed Godwits is that birds are being affected by change – individuals do not have the knowledge or flexibility to effect change. Even in long-lived birds, like Black-tailed Godwits, we see no evidence of individuals altering what they do over what is now two decades, despite the fact that the species’ migration dates, wintering areas and migration routes have all perceptibly changed over the same time period. It’s all about generational change. The behaviour patterns of young birds arise from the conditions they encounter in the first year of life, after which they are repeated.

Details of the Generational Change paper by Gill et al

blog LJ sum plumThe paper at the heart of this blog is: Mechanisms driving phenological and range change in migratory species by Jennifer Gill, José Alves and Tómas Gunnarsson, from the Universities of East Anglia (UK), Aveiro (Portugal) and Iceland. It is published in Linking behaviour to dynamics of population and communities: applications of novel approaches in behavioural ecology and conservation, a special issue of Philosophical Transactions B (Royal Society).

The paper could not have been produced without the help of “thousands of observers of colour-ringed godwits who have made these analyses possible”. This WaderTales blog is a celebration of the work they do: Godwits and Godwiteers.


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

 

Whimbrel: time to leave

blog WW-WLGeolocators* have provided fantastic information about the movements of migratory birds – making links between countries, revealing previously unknown stop-over sites and indicating just how quickly birds traverse our planet. A small number of Icelandic Whimbrel have carried geolocators for up to six annual cycles, providing Camilo Carneiro with an opportunity to investigate the annual consistency of egg-laying, autumn departure, arrival in West Africa, departure in the spring, stopover in Western Europe and arrival back in Iceland.

* Geolocators are tiny devices that record the daily positions of birds, by measuring the timing of dawn and dusk. An individual typically carries a geolocator for a year and then needs to be re-caught for the data to be downloaded.

Planning a trip

When booking a train journey on-line, the first question I am asked is whether I want to stipulate departure time or arrival time.  In early spring, with breeding on their minds, you might think that Whimbrel will focus on the time they need to be in Iceland, rather than the time they leave West Africa? If that’s the case then it might be best to take early spring opportunities if they arise, to catch express winds that will make the journey as rapid as possible and to get to Iceland early. Is that the case?

blog mangroves and beach

The Whimbrel is one of several wader species that breed in Iceland. Each autumn, Redshank, Snipe, Golden Plover, Oystercatcher and Black-tailed Godwit fly south to Europe, especially Ireland and the United Kingdom, but many Ringed Plover, most Dunlin and most Whimbrel travel as far as Africa. The main wintering sites for Whimbrel are in West Africa, south of the Sahara, in countries such as Guinea-Bissau. Here they can be seen feeding on crabs on the mangrove-fringed muddy shoreline (above). It’s a very different environment to the inland floodplains of Iceland (below).

blog river plain

In a paper by Tómas Gunnarsson & Gunnar Tómasson in 2011, we learnt that Whimbrel arrival times in Iceland did not change much between 1988 and 2009 (just 0.16 days earlier per year), while timing of arrival was advancing much more in species that travel less far to winter grounds, as you can see in this diagram.

wader arrival Tand G

Changes in first spring arrival dates of six species of waders in southern Iceland from 1988 to 2009 (reproduced from Gunnarsson & Tómasson 2011).

The arrival date for Black-tailed Godwit was advancing fastest (0.81 days per year). In more recent research, it has been shown that the rapidly advancing trend for Black-tailed Godwits is being driven by new recruits to the population – individual adults are not changing their schedules. Why is spring migration getting earlier? summarises a paper by Gill et al in Proceedings of the Royal Society B.

The Whimbrel trend has been recalculated, with a longer run of years, and the new change of 0.03 days earlier per year is not significantly different from zero. Given that Whimbrel are breeding alongside other species that are arriving in Iceland much earlier than thirty years ago, what are the constraints to the timing of their migrations?

Migration timings for Whimbrel

Camilo Carneiro, José Alves and Tómas Gunnarsson from the Universities of Aveiro (Portugal) and Iceland have been studying a population of Whimbrel in Southern Iceland. Birds are caught on the nest in one year and then re-caught in the subsequent year – or two years later if a bird evades capture in the intervening summer. The following results summarise weeks and weeks of patient fieldwork and brush over the hours of frustration caused by wary birds that have been caught before!

blog catching

Over the course of the whole study, 86 Whimbrel were fitted with geolocators, 62 of which were retrieved. Repeatability could be calculated for 16 birds, with between 2 and 7 years of data collected from each individual. The results are summarised in these few bullet points. Please see the paper for confidence intervals and more details about differences between the sexes.

  • Blog tagIndividual timings of autumn departure from Iceland varied between years. The repeatability index is 0.28, with a suggestion of a gender difference (females 0.40, males 0.02). Males tend to look after chicks for a longer period than females so their departure dates may be more strongly influenced by the success of each year’s breeding attempt.
  • Autumn arrival time in West Africa was closely linked to departure time because, on all but one occasion, southward migration was achieved through a single direct flight. See Iceland to Africa non-stop.
  • Spring departure time from West Africa was highly consistent, with a repeatability index of 0.76 and no discernible difference in repeatability between males and females.
  • blog long green grassSpring arrivals in Iceland. Some Whimbrel that managed to complete spring migration in a single flight in some years stopped off in other years. These breaks, perhaps to wait for more helpful wind conditions and/or to refuel, resulted in variability in annual arrival dates for individuals. The repeatability for the two sexes combined was 0.23.
  • Laying date was the least consistent stage of the annual cycle, with a repeatability index of 0.11 and no significant difference between males and females.

In an individual Whimbrel’s annual cycle, there appears to be one fixed point – departure from wintering ground in West Africa. With no discernible seasonality of resource availability on the wintering grounds and little change in day length in these areas, departure dates are probably being determined by an ‘internal clock’. Two major unknowns will then determine what happens in the next twelve months. Will wind and weather conditions be conducive to a one-leg flight to Iceland and how successful will a bird be in any particular breeding season? Unforeseen events, such as having to wait for a delayed partner, losing a first clutch, and the time needed to guard chicks will all affect the timing of autumn migration.

Understanding individuals

blog tag through grassThe study of wader migration has advanced hugely.

  • Fifty years ago, the main measure of migration phenology was the appearance of the first individuals of a species.
  • Colour-ring sightings are ideal for providing repeat arrival dates over the lifetimes of individuals, as exemplified by the Gill et al paper on Black-tailed Godwits, which suggest that individual timing is highly repeatable.
  • Geolocators have provided more detailed information about the precise arrival and departure timings of individuals, which is so important if we wish to conserve threatened, migratory species that visit areas in which data collection was previously virtually impossible.
  • Now, by tracking individual birds for several years, it is possible to look at the variability in annual patterns, and what can cause this variability.

Over the next decade or so, as devices get smaller and remote downloads become easier (eg using GSM tags), it should become possible to understand the conditions that lead to fast, slow and aborted migratory journeys in a whole range of species. Exciting times!

Paper

Why are Whimbrels not advancing their arrival dates into Iceland? Exploring seasonal and sex-specific variation in consistency of individual timing during the annual cycle. Camilo Carneiro, Tómas G Gunnarsson & José A Alves. Frontiers in Ecology & Evolution.

There is more about the information that is obtained from geolocators, how they work and the affects that they have on the individual birds that wear them in these two blogs:

blog roost flock


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

 

 

 

January to June 2019

blog CU postOne or two WaderTales blogs are published each month. The series is UK-based with a global reach. Suggestions of newly-published research on waders that might be of interest to birdwatchers who appreciate waders/shorebirds are welcomed. I am particularly keen to give feedback to colour-ring readers; they provide a huge amount of information that lies at the heart of these stories.

Click on a link in bold to read an individual blog.

You can sign up to receive an e-mail notification when a new blog is published.


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.

Not-so-Common Sandpipers

April and May mark the start of the Common Sandpiper breeding season, as males display along rivers and streams and around the banks of lakes and reservoirs. Numbers in the United Kingdom have declined by 26% in just over 20 years, providing an increased focus to research that has been taking place over five decades.

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This tale focuses on a year in the life of Common Sandpipers, using material gleaned from the book Common & Spotted Sandpipers by Phil Holland (published by Whittles in 2018) but with new information from recent migration studies. Phil’s fascinating book also includes chapters about the habitats used by both species, the food that they eat, predators that eat them and the way that Common Sandpipers have adapted (or failed to adapt) to changes in Britain over the last 250 years.

Common or Spotted?

blog spottyThis blog is just about Common Sandpipers. The Spotted Sandpiper breaks up the circumpolar distribution of the Common Sandpiper, laying claim to the Americas. A big difference between the two species is the mating system, with Common Sandpiper pairs setting up territories in a conventional (although not particularly faithful) manner and Spotted Sandpipers using polyandry in a way that provides females with the potential to raise more chicks in a year.

A female Spotted Sandpiper sets up a territory, attracts a male, lays a clutch of eggs which her partner then incubates, attracts and lays another clutch for another male, and so on. In Phil Holland’s book, there is an example of one female laying five clutches with three males over the course of six weeks – representing an egg-mass of four times her own body weight. There is plenty more fascinating stuff about Spotted Sandpipers in the book.

Population changes

The Breeding Bird Survey indicates a fall in breeding Common Sandpiper numbers in the UK of 26% between 1995 and 2017, with a bigger decline in England (49%) than in Scotland (23%). Other BTO-led surveys suggest that the nationwide declines started in the mid-1980s, with a British fall of over 50% during this longer period. There have been similar declines elsewhere in Europe. Common Sandpiper is now amber-listed, as a species of conservation concern, in the UK.

Breeding season

Much of the detailed breeding season work on Common Sandpiper in the UK was undertaken in the English Peak District by Phil Holland and then Derek Yalden, to whom Phil Holland’s book is dedicated, with information supplemented by other bird ringers, particularly Tom Dougall in Scotland.

blog nestMale Common Sandpipers tend to arrive back from Africa a little earlier than females – with a median difference of just two days – and it is the male that holds the territory (females in Spotted Sandpiper). If two birds that were together in the previous year arrive back on site then they will usually pair up again. When they don’t, it’s because of a mismatch in the timing of arrival or because the female moves to a better territory or more experienced mate. It may not be easy to spot infidelity in the field but genetic analysis in Scotland showed that males were incubating the eggs that had not been fertilized by them in 5 out of 26 cases (Mee paper link). On two of these occasions, none of the clutch of four belonged to the male that was sitting on them.

blog sittingDuring the incubation period, males typically take the 15-hour night-shift and females the 9-hour day-shift. During their ‘time off’, males devote time to territory defence and look-out duties. Chicks hatch after three weeks and the growth rate of chicks is highest in warm, dry and sunny weather. Males do most of the parenting of chicks; females usually leave before the chicks fledge and occasionally, if there are late nests, before the eggs hatch. Experienced parents raise more chicks to the point of fledging. There is more fascinating detail in the book, which includes full references for papers.

The southward migration

blog mapMovements of ringed birds from Scotland and Northern England strongly suggested that adults left their breeding territories and headed south within the UK, to fatten up prior to migration to Africa. British ringers have caught birds weighing up to 80 g, twice the pre-fattening weight, suggesting the potential to move a long way in the next flight.

Geolocators have been a revelation, enabling individuals to be tracked for the whole annual cycle between one breeding season and the next. The story of the first UK Common Sandpiper to return with a functioning geolocator was told in Wader Study by Brian Bates and colleagues, revealing two stops in western Britain, a three-day break in Morocco and a direct flight to Senegal.

There’s a WaderTales blog about the use of geolocators on Green Sandpipers that gives more information about how data are collected and discusses how these devices affect the behaviour of the birds that carry them.

A follow-up paper by the same Scottish team from Highland Ringing Group, this time with Ron Summers as lead author, has been published in the Journal of Avian Biology (Non-breeding areas and timing of migration in relation to weather of Scottish-breeding common sandpipers). It summarises the journeys of 10 tagged birds, with a median departure date from Scotland of 9 July. Some individuals spent time fattening in England, then most birds staged for longer in Iberia before continuing to West Africa, with a median arrival time of 28 July. The southward migration from Scotland took an average 17.5 days (range 1.5–24 days), excluding the initial fuelling period.

Pere Josa and colleagues have studied Common Sandpipers in The Ebro Delta of Spain, writing up their findings in Wader Study as Autumn migration of the Common Sandpiper. These stop-over adults migrate seven weeks earlier than juveniles, putting on enough fat to travel at least 2000 km on the next stage of their journeys, which would take them to North Africa. They would need to refuel if they were to make it as far as West Africa, which is the main wintering area for Common Sandpipers. Common & Spotted Sandpipers provides many more examples of ringing and body condition studies carried out in stop-over sites between Sweden and Morocco.

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Life in the south

blog mangroveSix of the tagged birds from Scotland spent most of the non-breeding season (October–February) on the coast of Guinea-Bissau, suggesting that this is a key area. Single birds occurred in Sierra Leone, Guinea, the Canary Islands and Western Sahara.

Coastal West Africa provides two major habitats for Common Sandpipers: mudflats associated with mangroves (as shown to the right) and rice fields. Phil Holland takes the reader around the mangroves of the world and discusses the numbers of Common and Spotted Sandpipers that have been reported from different countries. He suggests that rice fields provide supplementary food for birds that are mainly coastal winterers and wonders if the depletion of mangrove habitat  has affected Common Sandpipers.

The northward migration

The last day in West Africa, for the 10 tagged individuals, ranged from 3 to 20 April and the arrival dates in Scotland ranged from 19 April to 6 May. The birds typically staged twice between Morocco and the Channel and the median time taken for active migration was 16 days (range 13.5–20.5 days). The main migration strategy involved short- and medium-range flights, using tail-winds in most cases. Birds that left later spent shorter periods of time at stop-over locations.

Why so few Common Sandpipers?

survival blogAs discussed in the WaderTales blog summarising Patterns and processes in shorebird survival rates: a global review by Verónica Méndez in IBIS, the apparent annual survival rate of the Actitis family is low, with a calculated rate of 0.718 for Common Sandpiper and 0.497 for Spotted Sandpiper. Whether this has always been the case is unknown, of course, and Phil Holland points out that these calculations are based upon observations of colour-ringed individuals, at least some of which change territories between years, potentially leading to a reduction in detectability.

An analysis of demographic data for a small population of Common Sandpipers in northern England, by James Pearce-Higgins and colleagues indicated that the long-term decline in numbers was not due to low breeding success, instead being due to a low return rate of adults, which was negatively associated with the winter North Atlantic Oscillation. This suggested that climate change might be affecting annual survival.

In their paper about the 10 Scottish birds, tracked using geolocators, Ron Summers and colleagues matched movements to meteorological data during the migration period. They suggest that the weather during the southward migration was unlikely to adversely affect birds but that strong cross-winds or head-winds during the northward migration to the breeding grounds may do so. This accords with work on Black-tailed Godwits by Nathan Senner and colleagues which showed that the survival of satellite-tagged birds was reduced on the northward crossing from West Africa to Europe.

For the moment, there is no clear explanation for the fall in Common Sandpiper numbers. Given that it’s hard to change the climate or to study what might be happening to Common Sandpipers feeding amongst the mangroves of West Africa, it seems wise to focus on habitat and species protection in breeding areas. We also need to keep monitoring productivity and return rates of breeding populations in the UK and elsewhere, especially in the English Peak District.

Common & Spotted Sandpipers

blog coverPhil Holland’s book is a fascinating insight into the lives of the two Actitis species. It’s almost as if the reader is allowed to sit on a bank with the author and share intimate moments with these birds. Derek Yalden would have been delighted to see the project come to fruition but acknowledge that there is still much to learn. Who will spend the next 40 years studying Common Sandpipers in Europe and Africa or Asia and Australasia, or Spotted Sandpiper in the Americas?

Book Details

Common & Spotted Sandpipers is published by Whittles Books. You can find out more by following this link.

New research

blog CKThomas Mondain-Monval (Lancaster University) is trying to understand the UK-decline of Common Sandpipers.  He is studying a breeding population in the Yorkshire Dales National Park, tracking birds on migration and studying them at a wintering site in Djoudj National Bird Sanctuary, Senegal.  Birds are fitted with colour rings and geolocators in the UK and Senegal, and Thomas would appreciate reports of migrating birds, which are likely to appear in Iberia, France and England. If licensed bird-ringers see birds with geolocators and spot opportunities to catch them and remove the trackers, this would be very helpful. Thomas can be contacted at:

t.mondain-monval@lancaster.ac.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

From local warming to range expansion

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

Setting the scene

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

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

A booming population

godwit spread

Expanding breeding range in Iceland

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

blog chicks in nest

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

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

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

Catch your godwits

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

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

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

blog pete ruth

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

Major Findings

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

blog nest comparison

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

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

Are these findings applicable to other species?

blog cr juvenile

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

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

Paper

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

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Juveniles gather together in the late summer, prior to departure


GFA in Iceland

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

 

Iceland to Africa, non-stop

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

Migratory journeys

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

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

blog graphic

A sense of urgency

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

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

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

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Wintering Whimbrel in Guinea-Bissau

Results

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

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

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

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

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

Explaining the patterns

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

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

  • blog mangrove

    Whimbrel roosting in the top of mangroves at high tide

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

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

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

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

More about migration

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

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

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

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

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

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

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

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

 


GFA in Iceland

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

 

 

 

Head-starting success

The first year of head-started Black-tailed Godwits

blog RLGE

Head-started bird from 2017

As I write this, the Scientific & Technical Advisory Group of Project Godwit is meeting to review progress. They will be learning about the success of the project, which has three aims: to create the best possible habitat for the small (and threatened) population of Limosa Black-tailed Godwits breeding in the East Anglian washes, to provide protection for nesting pairs and to augment chick-production using head-starting. Head-starting involves removing first clutches and hand-rearing chicks before releasing them back to the wild. All of this is set within a rigorous scientific framework, so that the efficacy of head-starting and nest-protection can be carefully evaluated.

Success!

What a year it has been! When I wrote Special Black-tailed Godwits last year, I finished by saying, “Imagine how exciting it will be if one of this year’s head-started birds is found breeding in the Nene or Ouse Washes next year”. Amazingly, nine of the 26 head-started birds from 2017 were back this year and two females definitely had nests, with one fledging a chick, and a further two paired together are suspected to have attempted to nest. From data shared with me by Roos Kentie, this return-rate is comparable to wild-breeding Limosa Black-tailed Godwits in her Dutch study-area.

Earith 2

Where did the chicks go?

The left-hand map below shows the finding locations of chicks in the period June to September 2017, before they headed south for the winter. There had been a major publicity campaign, asking birdwatchers to look out for these special godwits in East Anglia. The Project Godwit team were pleased to receive news of six birds in Norfolk, Suffolk and Essex. The bird that turned up at Steart Marshes, in Somerset, came as more of a surprise.

headstarted map

Most limosa Black-tailed Godwits spend the winter in Africa, south of the Sahara, but an increasing number now stay in Portugal and Spain. There is a WaderTales blog about some of the costs and benefits of this new strategy: Should Black-tailed Godwits cross the Sahara? There were no winter sightings of the head-started birds but several popped up again in the spring of 2018, as shown in the right-hand map above. Four birds were seen in Portugal, two in France and one in Belgium. The Belgian sighting was the only unexpected sighting, as discussed in Site-fidelity in Black-tailed Godwits.

What about ‘wild’ birds?

wild mapRSPB scientists have been using colour-rings to follow the movements of Nene and Ouse Washes Black-tailed Godwits since 1999. As you can see, from the map alongside, the pattern of sightings is very similar to the one for the head-started birds, the only difference being a couple of winter reports in Senegal of the same individual and a bird that spends each winter in Portugal. August and September sightings have been in East Anglia, Spain and Portugal, with February and March sightings in Portugal, Spain, France and East Anglia.

As Black-tailed Godwits move north in February and March, they mix with birds of the islandica race which are preparing for the journey to Iceland. There’s a blog about the two subspecies here: Godwits in, Godwits out: Spring-time on the Washes.

Using geolocators

One of the outstanding questions is ‘Do head-started birds migrate in same way and spend the winter in the same places as birds that were raised naturally’. Given that released chicks have generally behaved just like other youngsters, they probably do, but it would be nice to have proof. To provide an answer, geolocators have been attached to the flag-type ring on each of 22 head-started chicks and 20 wild godwits. When they return (and if they can be caught on their nests) these geolocators will be taken off and the data will be downloaded. Keep an eye on the Project Godwit website for new information.

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Newly-tagged adult is released

Geolocators do not only reveal the final destinations of migratory birds, they also provide information about stop-over sites. Given that the limosa species is in serious decline (there’s a blog about the 75% drop in the Dutch population), it is important to understand the habitat requirements and timing of movements during migration. Two adult birds from the Nene have been tracked using geolocators, both of which spent the winter in Senegal.

The class of 2018

morgan 2018

‘Morgan’ is one of the class of 2018. This chick has already been seen in Hampshire and hopefully the geolocator (attached to green flag) will reveal where it spends the winter.

And so to the second year… As you can read here, 2018 was a strange breeding season. It started with a flood and ended with a drought. A total of 55 eggs were taken from the Nene Washes, including early eggs that had to be rescued from a waterlogged wheat field. Despite the muddy state of many of the eggs, 38 chicks were reared successfully and the first five were spotted away from the Welney and Nene release areas before the end of July – four on the North Norfolk coast and one at Titchfield Haven, in Hampshire.

These sightings and all the others that will hopefully be reported in August and September, are really valuable. They confirm which birds have survived their first few weeks and months in the wild and give a good clue as to which birds the team might see next spring. If you see one of the young birds, which carry a lime E ring on the right leg, please report it via this website.

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Funding

Project Godwit is a partnership between RSPB and WWT, with major funding from the EU Life Nature Programme, The HSBC 150th Anniversary Fund, Natural England, the Heritage Lottery Fund, through the Back from the Brink Programme and Leica UK.


GFA in Iceland

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

 

 

Fewer Spotted Redshanks

blog stalkingIt’s usually a good day if you see a Spotted Redshank in Britain or Ireland. How about a flock of 60?

On 27 July 1975, I was fortunate to be part of a Wash Wader Ringing Group cannon-netting team that caught 60 Spotted Redshanks at Terrington, on the Lincolnshire border of Norfolk. When we fired the nets, we knew that there were some Spotted Redshanks in the catching area but, as these birds were part of a mixed catch of 414, most of which were Redshank and Dunlin, the total number of these elegant ‘shanks came as a very welcome surprise. Why so many, what did we learn about Spotted Redshanks and what do we know now?

How to catch Spotted Redshanks

blog water groupThe spring of 1975 was very wet in East Anglia, with twice the annual monthly rain as is normal in April. Pools formed in fields, seed failed to germinate and there were many bare patches in cereal crops. Rather than leave a muddy pool to bake in the summer sun, a tidy-minded Terrington farmer decided to cultivate a strip through the corner of one of his fields, very close to the sea-wall. Conveniently, he created an area that was just the right width in which to set cannon-nets, meaning that any birds that chose to roost on the bare part of the field over high-tide were almost bound to get caught. It is unlikely that we missed many other Spotted Redshanks when we caught our 60.

This was actually the second catching attempt on the site. Two weeks earlier, on the previous set of spring tides, we had caught 460 birds in two catches – mostly Dunlin and Redshank but with one Spotted Redshank. In the previous 15 years, WWRG had caught just two Spotted Redshanks but more than 4000 Redshanks. Across the whole of Britain & Ireland, between 1909 and 1974, a grand total of 169 Spotted Redshanks had been ringed, which again puts the figure of 60 into perspective.

Where did they go?

The Spotted Redshanks we see in Britain & Ireland are assumed to breed in boggy woodlands in northern Scandinavia and Russia but there are no recoveries of ringed birds to prove this. Prior to the Terrington catch, there had been two foreign recoveries of BTO-ringed birds. A bird caught in Essex in August 1963 was caught by a Dutch ringer in May 1967, presumably on spring passage. Another, caught in July 1966 in Kent, was shot in Malta in April 1968, on its way back from an unknown wintering location in Africa.

blog swimmingThere have been two foreign recoveries of the Terrington birds, caught on 27 July 1975; amazingly both were in Morocco. The first was shot in March 1976, perhaps on its way north, but the second, shot in January 1983, may well have been wintering in North Africa. There has been one other foreign recovery of a WWRG since 1975; a bird ringed by WWRG in August 1978 was shot in Italy in March 1979, presumably on spring migration. This was the only Spotted Redshank ringed by WWRG in 1978. Six Spotted Redshanks have been recovered in France since 1975.

According to the 2016 BTO Ringing Report, a total of four foreign-ringed birds have been found in the UK. Two Dutch birds have been found dead at Hayling Island, Hampshire (January) and Tetney Lock, Lincolnshire (January) and a third bird was present at Titchwell, Norfolk in the summers of 2013 and 2016, where the ring was read in the field. A bird ringed in Germany on 10 August 1972 was recaught by ringers at Eyebrook Reservoir, Rutland, 23 days later.

The Terrington-ringed bird shot in Morocco in 1983 still represents the BTO longevity record for the species (7 years 5 months 16 days); this is similar to records set by Finnish and Dutch ringed birds. (There is a WaderTales blog about longevity in waders here)

Summering Shanks?

Many of the Spotted Redshanks we caught on the Wash in 1975 were thought, at the time, to be summering, first-year birds but these were in the days before the publication of the Guide to the identification and ageing of Holarctic Waders (Prater, Marchant & Vuorinen, BTO) and I do wonder whether early onset of moult may have led to some ageing errors. We now know that females can moult very early, having left their partners to finish brooding their eggs and bring up the chicks. Some of their moult can take place near their breeding grounds, which could mean half-summer plumage birds arriving in July. Alternatively, birds could have arrived in June and already be in moult. Had the wader guide been available in 1975, we might have been able to separate out full-plumage males and females by looking at the central under-tail coverts and the edges of the head feathers. Next time …

blog BirdTrackThe latest BirdTrack graph gives pretty clear evidence that there is a gap between the end of spring migration and the start of autumn passage. However, as you can see, it’s short; just the end of May and the start of June. It has been suggested that not all first-year Spotted Redshanks travel to the breeding grounds, with some staying in their wintering grounds and others completing only part of the journey north. The few birds that are still in the UK in the May/June gap could be some of these one-year-old individuals or full adults not in condition to breed.

Looking at numbers

blog booksAs I prepared for this article, I turned to Twitter to see how unusual the Terrington catch had been, simply in terms of the number of birds counted in flocks. There have been some recent largish counts, including one of 52 at Old Hall Marshes (Essex) in September 2017 and 32 at Blacktoft Sands in Yorkshire in 2015 but, interestingly, I learnt that bigger flocks were mostly historical. According to the three books, The Birds of Norfolk, Suffolk & Essex, the three peak counts have been 187 at Snettisham in 1977, 112 at Minsmere in 1991 and 127 on the River Colne in 1972. Kent beat these East Anglian county records with a maximum of 220 at Grovehurst on 8 October 1972 (Birds of Kent, 1981).

This story from Northumbrian Birds illustrates a typical recent trend. Here, the record counts were of 27 and 21 at Lindisfarne in 1974 and 1976 but there has been a maximum count of just 7 in the last ten years. At the other end of England, Steve Rogers reported that he had 45 at Ruan Laniholme in Cornwall in 1977 but that “you’ll be lucky to see one” now. This is just a small selection of the comments received from a wide spread of  places, including Poole Harbour in Dorset and Cork in Ireland.

blog WeBSPotentially, the development of new nature reserves around the coast and along our river valleys might have created new opportunities for Spotted Redshanks, with birds spreading out across more sites and hence in lower concentrations? To get a national viewpoint, I turned to the online report from the monthly Wetland Bird Survey (WeBS). What did winter counts by volunteers from across the United Kingdom tell us about what has been happening to the species over the period since 1975? As you can see from the graph alongside, the index has dropped by 50% since the start of this century, in line with the local information for late-summer passage discussed above. (There is a WaderTales blog about WeBS here).

Conservation concerns

According to the BirdLife International species fact-sheet, as downloaded from http://www.birdlife.org on 25/07/2018, Spotted Redshanks are of ‘Least Concern’, largely because the large breeding and wintering ranges (map below) reduces the risk of extinction. Breeding numbers are hard to monitor, due to the low densities in the wooded marshes near the tundra edge, and the series of winter wader counts for the UK is much longer and more comprehensive than any other country in the wintering range. Perhaps there would be more concern if there were other international counts that showed the same sort of declines as seen in the UK?

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BoCC4Here, Spotted Redshank is listed as amber, rather than green, simply because the estimated winter count of about 100 is large in a western European context. Perhaps a decline of 50% should create pressure to change amber to red or, more importantly, to revisit the ‘Least Concern’ designation. Whilst it might be hard to target conservation action at a species which uses such a wide range of breeding, passage and winter locations, perhaps we should acknowledge that, according to what is probably the best evidence available, we are seeing a rapid decline?

Our catch of 60 Spotted Redshanks in 1975 is an amazing memory but concentrations in these numbers could be found at a number of sites on the east coast between at least 1964 and the end of the 20th Century. For the moment, we must acknowledge that UK autumn flocks of 60 are largely a thing of the past. Perhaps flocks of 30 might soon be consigned to history? Keep counting!

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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

 

Mission Impossible? Counting Iceland’s wintering Oystercatchers

If Norwegian Oystercatchers migrate south and west for the winter, how is it that thousands of Oystercatchers can adopt a stay-at-home strategy in Iceland, which lies at a higher latitude than most of Norway?

Braving the cold

As part of a project to try to understand why some Oystercatchers spend the winter in Iceland, when most fly south across the Atlantic, researchers needed to count the ones that remain. Unlike in the UK, where the Wetland Bird Survey can rely on over 3000 volunteers to make monthly counts of waders and waterfowl, it’s tough to organise coordinated counts of waders in Iceland. Winter weather, a small pool of birdwatchers and short days don’t help when you are trying to cover the coastline of a country the size of England.

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Up until 2016, the only winter wader data in Iceland came from Christmas Bird Counts, first run in 1956. These coordinated counts suggested that most Oystercatchers were to be found in southwest and west Iceland, which is also where most birdwatchers live, but with smaller numbers in areas such as the southeast. The maximum number of Oystercatchers found in any one year was 4466 birds but this excluded known wintering sites which were inaccessible or very hard to access. Some contributors to Christmas bird counts live in areas away from the well-populated west of the country, and they provided evidence that there were no Oystercatchers in the north, for instance. This information gave some guidance as to where to look for Oystercatcher flocks but could a small team of researchers and birdwatchers do a complete count of the resident component of the species in the middle of winter?

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Part one of the survey involved a group of well-prepared birdwatchers and researchers spending several days counting Oystercatchers in as many areas as possible of the southeast and in the whole of the west, from the southwest tip of Iceland (where Keflavik airport is situated) through to known wintering locations in the northwest fjords. The north and south coasts could largely be discounted; the north is too cold and the south coast is very barren.

Part two of the survey was carried out by air, allowing the addition of counts of the islands and inaccessible coastal sites in the Breiðafjörður Bay, as well as some key sites in Faxaflói Bay (see map). Flocks of roosting Oystercatchers were usually seen from afar and photographs were used to make counts without flushing the birds.

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Survey results

The ground-based wader surveys were carried out between 28 January and 3 February 2017 and the aerial survey took place on 16 February. In total, 11,141 Oystercatchers were counted, which nearly triples the previous Christmas total. As expected, the vast majority of Oystercatchers were found on wintering sites in SW and W Iceland. Large numbers of birds were found on sites not covered by the Christmas counts, particularly on the north side of Faxaflói Bay and during the aerial survey over Breiðafjörður Bay.

blog BoddiThe full results of the paper are presented in a new paper in the BTO journal Bird Study. (Click on title for link)

Population size of Oystercatchers Haematopus ostralegus wintering in Iceland Böðvar Þórisson, Verónica Méndez , José A. Alves, Jennifer A. Gill , Kristinn H. Skarphéðinsson, Svenja N.V. Auhage, Sölvi R. Vignisson, Guðmundur Ö. Benediktsson, Brynjúlfur Brynjólfsson, Cristian Gallo, Hafdís Sturlaugsdóttir, Páll Leifsson & Tómas G. Gunnarsson.

Resident or migrant? 

One of the key questions that researchers wanted to answer was ‘what proportion of the Icelandic breeding population is migratory?’ This is part of a bigger project exploring the causes and consequences of individual migratory strategies, as you can read in the previous WaderTales blog: Migratory decisions for Icelandic Oystercatchers. This project is a joint initiative by the universities of Iceland, East Anglia and Aveiro, led by Verónica Méndez.

blog familyIn order to estimate the proportion of migrants and residents it was necessary first to determine the total size of the Icelandic Oystercatcher population, based on a recent estimate of 13 thousand breeding pairs (Skarphéðinsson et al. 2016) . How many sub-adults are there to add to the 26,000 breeding birds?

Verónica Méndez and her team have shown that Oystercatchers fledge on average about 0.5 chicks per pair. Using estimates that 50% of these chicks are alive by mid-winter, that there is then a 90% chance of annual survival and birds typically breed when they are four years old, it was possible to come up with a total population of just over 37,000 birds.

Although the authors of the paper have produced the best winter estimate thus far, they note that it is a minimum – there could be small numbers of birds in other areas. At 11,141 out of 37,177 birds, the minimum estimate of the residential part of the population is 30%, leaving 70% to be distributed around the coasts of the British Isles and (in smaller numbers) along the coastline of mainland Europe.

Latitudinal expectation 

blog ringed birdTo put the migratory status of the Icelandic Oystercatcher into context with other Oystercatcher populations breeding in NW Europe, the authors collated information about the proportion of resident and migratory Oystercatchers in coastal countries between Norway and the Netherlands. They show that there is a strong latitudinal decline in residency. From Northern Norway (69.6°N) to Southern Sweden (57.7°N), where mean January temperatures are typically in the range of -1 to -4°C, only occasional individuals are found in winter, whereas populations in Denmark (55.4°N), where mean January temperatures 0.8°C, and sites that are further south and warmer mostly comprise resident individuals.

blog scenicThis cline in migratory tendency is also seen within the British Isles, which stretch from 60.8°N to 50.2°N. Writing in the BTO’s Migration Atlas, Humphrey Sitters reports that birds from the north of the British Isles have a median recovery distance of 213.5 km, whereas in the west, east, south and Ireland the respective figures are 35.5, 27.0, 6.0 and 13.5 km. In each group, there are birds that travel over 800 km, implying some degree of migratory tendency in birds breeding in every part of the British Isles.

Iceland lies between 63.2°N and 66.3°N, which puts it well within the latitudinal range of the ‘almost-all-migrate’ group of Scandinavian birds. The Icelandic proportion of 30% residency is likely to be a function of the temperature and geographical isolation of the island. Bathed by the relatively warm waters of the Gulf Stream, some coastal areas, particularly in the west of Iceland, provide a relatively mild oceanic climate and apparently ample food stocks to support high survival during most winters. On the other hand, days are very short. For an Oystercatcher that spends December in Reykjavik, the time between sunrise and sunset is just four hours and the average January temperature is -0.6°C. For a bird in Dublin day-length figure is almost twice as long, at seven and a half hours, and temperature is 5.3°C. Food availability may well be compromised by the time available to collect it, as previous studies have shown that feeding efficiency is on average lower at night.

blog of other wadertalesIceland might hold a higher proportion of residents than would otherwise be the case as it is far enough away from Britain (about 750 km to mainland Scotland) and Ireland for the sea crossing to potentially be a significant barrier. For migrants, time will need to be spent acquiring the reserves needed for the journey south in the autumn and north in the spring and the flights may well add costs in terms of survival probability.

There is a blog about the broader project to understand how individual birds become ‘programmed’ to be migrants or residents here: Migratory decisions for Icelandic Oystercatchers.

The migration option 

blog sightingsIf 30% of Oystercatchers are staying in Iceland this implies that up to 26,000 birds of Icelandic origin are to be found in the British Isles and on the western coast of Europe during the winter. Some of these – young birds that are yet to breed – can be found in these areas in the summer too. By the end of the summer of 2017, Verónica Méndez and her team had colour-ringed about 800 (500 adults, 300 juvenile) birds in Iceland, in order to try better to understand the reasons for the migratory/residency decisions that individuals make. Every dot on the map alongside (which was created on 1st June 2018) represents a migratory bird. Each record is valuable and there are lots more birds to try to find! Are there really no Icelandic Oystercatchers in the vast flocks of eastern England?

If you come across a colour-marked Oystercatcher, please report it to icelandwader@gmail.com 

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GFA in Iceland

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