Whimbrels on the move

You may hear the distinctive seven-note call of a Whimbrel overhead in late April or May but where is it going and where has it been?

Many pairs of Whimbrel nest in the flood-plains of Iceland’s rivers (Tómas Gunnarsson)

In a 2016 paper in Wader Study, Tómas Gunnarsson and Guðmundur Guðmundsson analysed the ringing recoveries of Icelandic Whimbrel and demonstrated that many probably make non-stop flights from Iceland to western Africa.  The study also helped to explain the timing and origins of flocks of Whimbrel in different parts of the British Isles in spring and late summer.

Migration and non-breeding distribution of Icelandic Whimbrels Numenius phaeopus islandicus as revealed by ringing recoveries: Tómas Grétar Gunnarsson and Guðmundur A. Guðmundsson (Wader Study). The paper is available here.

Since the publication of this paper, further details has been added using geolocators, small tags that collect information on the movements of birds over a twelve-month period, and now using satellite tracking. There’s more about this work at the end of this blog.

Whimbrels in Iceland

It is estimated that 250,000 pairs of Whimbrel  breed in in Iceland, representing 25% of the combined global population for all seven subspecies of Whimbrel and making Iceland a very important country for the species. The Icelandic breeding population is believed to be relatively stable but others, such as those in North America, are in decline.

There are two blogs about how volcanic dust affects Whimbrel. In the long-term volcanic ash provides important fertilizers but short term effects can be seen in breeding success.

The Whimbrel is one of the commonest of Iceland’s breeding wader species, with most nests estimated to be at elevations lower than 200m and particularly along river flood-plains.

Iceland is a country in a state of constant flux, both because of geothermal activity and the subsequent physical processes associated with wind and water flow, and as a result of human interventions. Volcanic ash has been shown to affect the breeding success of Whimbrels in the short term and their distribution in the longer term. Land use is also changing rapidly, particularly as a result of afforestation and the ways that land is farmed, and work is ongoing to understand how these processes might impact upon breeding waders, including Whimbrels.

Movements of Icelandic Whimbrel

Nesting Whimbrel hunkers down in heathland vegetation – a very different habitat to the mud and mangroves of West Africa (Tómas Gunnarsson)

Over 6000 Whimbrels have been ringed in Iceland since 1921, with 95% of these caught as chicks. 35 Icelandic-ringed Whimbrels have been recovered abroad and 4 foreign-ringed Whimbrels have been found in Iceland.  In their paper, Tómas and Guðmundur show that most of the winter records of Icelandic birds are in west Africa, between Mauritania in the north and Benin and Togo in the south, but that there are two January records in Spain, suggesting that some individuals don’t travel further south than Europe.  Spain and Portugal cannot be particularly important wintering areas for the species, however, as Whimbrel counts across Spain and Portugal don’t exceed 1000 birds, which represents a tiny part of the Icelandic population, even if they are all assumed to originate from there.

Reproduced from Gunnarsson & Gudmundsson 2016 with permission from Wader Study

Spring and autumn Whimbrel records that link Iceland with Britain and Ireland show strikingly different distributions for the two seasons.  There are eight recoveries in the British Isles on spring passage; 1 in Ireland and 7 in western counties of the UK. There is only one autumn passage record (in the Outer Hebrides), despite the fact that autumn shooting of Curlew, which did not stop until 1981, might have been expected to have produced recoveries of similar Whimbrel. This strongly suggests that, while some whimbrel stop off on northwards migration, the southerly journey is straight to Africa. We know that this is possible, because a satellite-tagged Whimbrel was tracked making a direct flight from Iceland to Guinea-Bissau in late summer 2007.

Counts and recoveries of British birds

Some of the big WeBS counts for Whimbrel are made in the late summer, with over 1500 birds reported on the Wash (August), nearly 300 along the North Norfolk coast (August) and nearly 200 in July in each of Chichester Harbour (Hampshire) and Morecambe Bay.  Largest counts in spring are mainly in the west and all in April, with 331 on the Severn, 339 on the Ribble and 654 in the Fylde area but one east coast site (Breydon Water in Norfolk) has had a spring count of 137. Although April & May flocks might seem large, they should be viewed in context – at least 500,000 Whimbrel travel back to Iceland each year.

The only British-ringed Whimbrels to have been found in Iceland have been two satellite-tagged birds, one of which is mentioned above, but metal-ringed birds have returned to breeding grounds in Finland, Russia and Sweden. Given that this new paper suggests no links between eastern Britain and Iceland in the autumn, it is likely that the large number of birds that spend the moult period on east coast estuaries such as the Wash are mainly of continental origin. The same is probably true for late-summer gatherings, such as the ones in Chichester Harbourand Morecambe Bay.

Tómas Gunnarsson

In order to understand more about spring flocks of Whimbrel in the UK, ringing and satellite tagging has been taking place in the Lower Derwent Valley (East Yorkshire). Birds tagged here have flown to both Iceland and Sweden which indicates that Icelandic and continental birds gather together in April and May flocks. Despite this mix of subspecies in Yorkshire, the lack of ringing recoveries of Icelandic birds in the east of the UK suggests that continental birds make up the majority of spring flocks in the east.

To summarise: if you hear a Whimbrel calling overhead in the autumn it is probably of continental origin, especially in the east. On spring passage, a seven-note call in the west may well have an Icelandic twang but in the east it could sound that little bit more Scandinavian. If only we could tell them apart.

To learn more about the migration of over 40 wader species to, from and through Britain & Ireland, check out this WaderTales blog.

Update: Tracking helps to provide more insights

Tómas Gunnarsson

This analysis of metal-ringed birds set the context for new studies to understand the migration strategies of individual Icelandic birds, using geolocators and satellite tags.

The first paper using these data appeared in Nature’s Scientific Reports. In it, José Alves and his colleagues show that four birds completed the autumn migration in one flight. On return in spring, two of these birds stopped off in Ireland and two flew straight to Iceland.

Camilo Carneiro developed the work further, working with supervisors Tómas Gunnarsson and José Alves. By increasing the sample size of birds carrying geolocators from Iceland and back again, he was able to show that all of the adults in his sample were able to migrate directly from Iceland to West Africa at the end of the breeding season. Only 20% of journeys north in the spring were completed without refuelling. Most of these stops were in Ireland and western Britain, as predicted from the results of the ringing analyses summarised above. See Iceland to Africa non-stop.

By tracking birds in more than one year, Camilo has gone on to show that the fixed point in an Icelandic Whimbrel’s annual cycle is spring departure from Africa. See Whimbrel: time to leave.

With further research it should soon be possible to understand how these epic sea crossings from Iceland to Africa are affected by prevailing winds and varying weather patterns, whether individuals use the same strategies in different years and if a juvenile can make it all the way to Africa on its maiden flight.

Meanwhile, you can help with the studies of migration by looking out for and reporting colour-ringed Whimbrel. Most of the ones seen in Britain & Ireland will have been marked by researchers in Iceland and they will be delighted to hear news of their birds at icelandwader@gmail.com.

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

@grahamfappleton

Godwits in, Godwits out: springtime on the Washes

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

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

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

Limosa godwits

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

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

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

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

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

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

Limosa or Islandica?

The forehead is more prominent in islandica (Pat Wileman)

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

Islandica godwits

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

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

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

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

Conservation importance for islandica

Graham Catley

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

New hope for limosa breeding in the Ouse & Nene Washes

Nene Washes RSPB reserve (RSPB)

These are exciting times for limosa godwits in the UK. The RSPB, in partnership with WWT, have attracted European funding for a five-year recovery project for these birds. Securing the future of the Nene-breeding godwits is central to this project, through increasing the area of suitable breeding habitat and improving predator management, alongside research to assess the success of these actions.

One of the key actions is to trial head-starting – taking a small number of early clutches of eggs and raising chicks in a predator-free environment. You can read more here. Project Godwit is a partnership between RSPB and WWT with major funding from the EU LIFE Nature Programme, HSBC, Natural England and the Heritage Lottery Fund.

Having only one really key breeding area always leaves a population vulnerable, so re-establishing more breeding populations on the newly created wet grasslands adjacent to the Ouse Washes is also critical to the future of Black-tailed Godwits, as a breeding species in the UK.

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

@grahamfappleton

 

Big Foot and the Redshank Nest

What’s the crunch point? Grazed saltmarsh is an important habitat for Redshank but the addition of an extra four large feet can have serious negative effects. 

Each grazing unit comes with four very large feet (Adam Cross)

In a 2016 paper in Agriculture, Ecosystems & Environment, Elwyn Sharps and colleagues from Bangor University, CEH and the RSPB have shown that there is a tricky balance between providing the open, grazed habitats in which Redshanks can breed and minimising the likelihood of nests being trampled by cattle. If only cattle could do their important habitat management work outside the nesting season? However, the grass keeps growing and these four-footed, saltmarsh mowing machines usually arrive on site in spring and stay throughout the summer.

Sharps, E., Garbutt, A., Hiddink, J. G., Smart, J., & Skov, M. W. (2016). Light grazing of saltmarshes increases the availability of nest sites for Common Redshank Tringa totanus, but reduces their quality. Agriculture, Ecosystems & Environment, 221, 71-78. 

Background

Distribution map from Bird Atlas 2007-11, which is a joint project between BTO, BirdWatch Ireland and the Scottish Ornithologists’ Club

In the United Kingdom, Redshanks are amber listed species of conservation concern, increasingly restricted in their distribution. The map alongside shows that breeding Redshanks have been lost from many areas (downwards pointing black arrows). More distribution maps from Bird Atlas 2007-11 can be found on the BTO Mapstore.

Although they breed in various grassland habitats, coastal saltmarshes are internationally important. The breeding population on British saltmarshes has reduced by over 50% since 1985. Declines have been linked to grazing management, as breeding densities are higher with light and moderate grazing than on heavily grazed or ungrazed saltmarshes (Norris et al., 1998; Malpas et al., 2013).

Intensive grazing leads to a very short, uniform sward, lighter grazing produces a more uneven patchy sward with diverse heights whilst no grazing can leave saltmarshes with dense communities of coarse grasses. For Redshank, which need clumps of grass in which to hide their nests and more open areas in which chicks can feed, light grazing is a key management tool.  Elwyn Sharps and his colleagues, working on the saltmarshes of the Ribble Estuary in northwest England, were interested to see just how light a grazing regime worked for the local Redshanks.

Working on the Wash, nearly twenty years previously, Ken Norris and colleagues had found that breeding densities were higher in structurally diverse grazed vegetation, and recommend low stocking densities of about 1 cattle ha^-1, in order to create a patchy vegetation sward, suitable for nesting Redshank. This falls within the UK Environment Agency definition of light saltmarsh cattle grazing of between 0.7 and 1 young cattle per hectare between April and October, which translates to an annual cattle density of 0.3 to 0.5 cattle per hectare per year.  Work on the Ribble suggests that light grazing can reduce nest survival both directly through nest trampling and indirectly through accelerating predation risks. Breeding densities may appear high in some areas but productivity can still be very low.

An earlier paper by Elwyn Sharps et al. showed that the risk of Redshank nest predation increased from 28% with no grazing to 95% with grazing of 0.5 cattle per hectare per year, which is still within the definition of light grazing. Some of the nest failures were due to trampling, with 1 out of 5 nests being affected in areas with the lowest stocking rates and 4 out of 8 in the most heavily stocked (though still defined as lightly-grazed) area.

What do Redshank need?

Crunch point: when a large foot meets a fragile clutch (Christine Tansey)

In lowland wet grasslands, Jennifer Smart demonstrated that Redshank select tall nest vegetation, with some additional cover in a wider 10m area around the nest. Elwyn Sharps investigated nest site selection by Redshank breeding in six lightly grazed saltmarshes around the Ribble in with cattle densities were between of 0 to 0.55 grazing units ha^-1 y^-1.  In May and June 2012, a total of 45 Redshank nests were found across the six saltmarshes (between 5 and 10 nests per marsh) and vegetation heights and species composition were measured at and in the vicinity of nests, as well as at control points.

Photo: Christine Tansey

On The Ribble, vegetation height was taller at, next to and in the wider area around nests, when compared to control points, for all spatial scales studied, in line with those found on lowland wet grasslands. The vegetation composition was different in the immediate vicinity and in the wider area around nests than at control points, indicating that Redshank select nest sites surrounded by particular species of vegetation. Most of the dissimilarity between nests and control points was due to red fescue (Festuca rubra), which was more abundant near nests than at control points. There is a suggestion from the Ribble data that Redshank select nests within communities of F. rubra, which is a species associated with cattle-grazing in higher elevation saltmarsh.

Implications for land management

Not quite long enough? Redshank nests are often completely hidden within clumps of grass (Kevin Simmonds)

The results of this study suggest that livestock grazing plays an important role in creating the F. rubra nesting habitat preferred by Redshank nesting on the Ribble Estuary. However, even low intensity conservation grazing can create a shorter than ideal sward height, potentially leaving Redshank nests more vulnerable to predators. Translating the UK Environment Agency light grazing guidelines of 0.7-1 young cattle per hectare between April and October to measurements used in this study would mean an annual cattle density of around 0.4-0.5 cattle per hectare per year, which this study suggests is too intensive for breeding Redshank.

Elwyn Sharps suggests that future solutions should focus on designing grazing regimes which increases sward heights for Redshank nesting. This could include delaying the start of grazing until most Redshank stop nesting in mid-July, but then grazing more intensively afterwards. This would allow vegetation to remain tall during the nesting season, but would still maintain a cover of F. rubra.

To read more about RSPB studies of breeding Redshanks visit this WaderTales blog (Kirsty Turner)

Another potential management solution may be a rotational grazing system, whereby saltmarshes are grazed and left ungrazed in alternate years, potentially improving habitat quality by allowing the vegetation to grow taller in the ungrazed year. However, on a small scale, Redshank may then select the part of a saltmarsh that was previously ungrazed , and therefore the area that will soon be grazed. It is clear that there are a number of possible solutions to this problem that require further investigations if the ideal saltmarsh management option for Redshank is to be ascertained. In working out how to manage saltmarshes for breeding waders, land managers will need to take account of the needs of other breeding species, overwintering wildfowl, and wider saltmarsh biodiversity, each of which may apply different constraints.

Sharps, E., Garbutt, A., Hiddink, J. G., Smart, J., & Skov, M. W. (2016). Light grazing of saltmarshes increases the availability of nest sites for Common Redshank Tringa totanus, but reduces their quality. Agriculture, Ecosystems & Environment, 221, 71-78.

And another problem…

In a more recent 2017 paper in Ecology & Evolution, Elwyn Sharps and colleagues show that cattle spend their time in the same areas of a saltmarsh as the ones in which Redshanks like to nest. Their conclusion is that “grazing management should aim to keep livestock away from redshank nesting habitat between mid-April and mid-July, when nests are active, through delaying the onset of grazing or introducing a rotational grazing system”.

Nest trampling and ground nesting birds: Quantifying temporal and spatial overlap between cattle activity and breeding redshank.

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

@grahamfappleton