Bar-tailed Godwits: migration & survival

Putting the flags out –  to learn more about one of the most amazing species of migrating wader.

Ruth banner

When we caught 505 Bar-tailed Godwits on the Wash, on the east coast of England, on 29 August 1976 we thought that we would add hugely to our knowledge of the species’ migration but we were disappointed. In the last six years, by adding leg-flags to just 248 birds, the Wash Wader Ringing Group has learnt a lot more.

Forty years ago

On 29 August 1976, in the days of stubble-burning, we had covered four cannon nets with fine, black burnt chaff to hide them almost completely. We knew that the big tide would push birds off the saltings and over the sea wall, there were decoys to pull the birds into the right 1% of a vast, flat field and the weather was good. Everything was ready. I was in a one-man, cabbage-crate hide, in line with my set of two nets. I remember seeing one Redshank look at the decoys and descend, pulling down a vast cloud of over 2000 Bar-tailed Godwits. There were some concerns about birds being too close to one of the nets on my line so we fired three nets, catching 505 bar-tailed godwits and 44 other waders.

Cathy ad and juv

Juvenile with moulting adult

A catch of 505 Bar-tailed Godwits seemed like a game-changer, including 22 that were already wearing rings. 483 new birds were bound to make a huge difference to our understanding of the species’ migration patterns and survival probabilities … surely? Up until that day, the Wash Wader Ringing Group (WWRG) had ringed a total of 1136 Bar-tailed Godwits so we were adding over 40% to the total, using harder rings with a much longer life-expectancy than those added as early as 1959.

This was a moulting flock; an autumn drop in numbers and a previous recovery of a bird in Spain suggested that many birds would spend the winter elsewhere but where? As luck would have it, only one of the birds from August 1976 has ever been found abroad – a bird shot in France in February 1985. The only British recoveries have been a bird found dead in Yorkshire in November 1976 and seven birds found around the Wash between 1979 and 1999. As to subsequent recaptures, 38 birds have been caught again by the WWRG, five of which were retrapped for a third time. With all the best models in the world, these figures are not enough to give a reasonable estimate of survival and there is no way that a change in survival rate could be picked up.

It’s pleasing to report that one bird was still alive on 21 February 2003 – over 28 years after ringing – but even this is not the longevity record for a BTO Bar-tailed Godwit. That’s held by another WWRG bird that was ringed on 22 August 1974 and last recaptured on 4 August 2008 – nearly 34 years later. Perhaps one of the 1976 birds is still alive and waiting to be caught again?

Bar-tailed Godwit migration

Since the 1976 catch, WWRG has been a bit more fortunate in its foreign recoveries of metal-ringed Bar-tailed Godwit, with 2 recoveries in Mauritania, one in Guinea Bissau and another on a ship off Guinea, out of a total of 12 BTO-ringed birds found in Africa. A bird caught in Teesmouth on 13 October 1982 was in Western Sahara five days later, which may give an indication of the timing of post-moult movement. The map alongside shows the full set of BTO recoveries (purple) and foreign-ringed birds found in Britain & Ireland (orange). The dots show the westward post-breeding movement from Russia to the Atlantic coast of Europe and the onward migration of thousands of birds to Africa.

One of the fascinating things about migration is the way that different populations of the same species have developed radically different migration patterns since the last Ice Age, the global maximum extent of which was reached only 20,000 years ago. At the same time that the Bar-tailed Godwits we see in Western Europe are making relatively modest journeys west and south in late summer, some of those of the baueri subspecies are undertaking nine-day, non-stop flights from Alaska to New Zealand. The physiological processes and navigational techniques that birds on the Pacific flyway have mastered would amaze their European cousins. To read more about flyway evolution for Arctic waders, and Knot on particular, see a Review by Theunis Piersema (Journal of Ornithology, 2011).

Conservation Status

Bar-tailed Godwits are classified as near-threatened by BirdLife International and the IUCN. There are four recognised subspecies facing various threats, as shown in the species fact-sheet here. 

Sam winter gloves

Bar-tailed Godwits wintering on the Wash are of the lapponica subspecies

Two subspecies visit the Wash; lapponica from Norway through to western Siberia and taymyrensis from central Siberia. Two subspecies, menzbieri and baueri, use the East Asian-Australasian Flyway and are both undergoing extremely rapid declines, in large part due to severe habitat loss in the Yellow Sea. As a result of severe problems for waders using this flyway, the species has been uplisted to Near Threatened (BIrdLife International).

Satellite-tagging has revealed the impressive trans-oceanic migration routes of individuals between Alaska and New Zealand and shown the importance of the Yellow Sea for birds as they return north in the spring. Colour-rings and flags have shown that there has been a sudden drop in survival rates for Bar-tailed Godwits and other species using sites in China and other rapidly developing countries of South-East Asia, leading to urgent calls for conservation initiatives at an international scale. You can read more about this emerging story in these three papers.

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Learn more about the amazing migration of Bar-tailed Godwits on the New Zealand Science Learning Hub

Contrasting extreme long-distance migration patterns in bar-tailed godwit Limosa lapponica. Phil Battley et al. Journal of Avian Biology. 10.1111/j.1600-048X.2011.05473.x 

Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Theunis Piersma at al. Journal of Animal Ecology. 10.1111/1365-2664.12582

Declining adult survival of New Zealand Bar-tailed Godwits during 2005–2012 despite apparent population stability. Jesse Conklin et al. Emu. http://dx.doi.org/10.1071/MU15058

For Bar-tailed Godwits wintering in western Europe there is currently less immediate conservation concern, although there are warming conditions in their breeding grounds and over-fishing and emerging diseases of shellfish are known to be affecting estuaries on both sides of the North Sea. Things are more worrying in West Africa, where numbers have declined from 746,000 to 498,000 over a period of 30 years, according to a report by van Roomen et al. Some of these birds spend time in the Wash in the autumn on their way south.

Status of coastal waterbird populations in the East Atlantic Flyway. With special attention to flyway populations making use of the Wadden Sea. van Roomen et al.

Flying the flag

Cathy gluing

Each bird wears a two-letter flag and a white colour-ring (shown here)

Given the worsening conservation status of Bar-tailed Godwits and the gaps in our understanding of what is happening to birds that visit the Wash, the WWRG decided that it would help if birds could be monitored through colour-ringing. That way, the movement and survival of individuals can be monitored using a telescope instead of relying on recapture.

The flagging of Bar-tailed Godwits on the Wash has dramatically increased the number of records of birds subsequent to ringing but the scheme is still in its early days. Flagging started in August 2010 but the first significant catch did not take place until 11 February 2012, when 56 birds was flagged. According to Phil Atkinson, who runs the WWRG database for the species, one third of the birds from this catch have been resighted alive in the four years since that catch (compared to 1% recapture rate for metal-ringed birds in the four years after the 1976 catch).

Cathy KAMost resightings have been on the Wash and those from elsewhere have tended to confirm what was known from metal ringing. A moulting bird on the Wash was seen on the Wirral (northwest England) in the same autumn, showing that birds moulting on the Wash can move elsewhere in Northwest Europe to winter. A non-moulting bird, caught at Terrington on 30 September 2011, was resighted at Ebel Khaznaya, Mauritania 50 days later. These two resightings confirmed that the Wash is an important site not only for the wintering Fenno-Scandinavian and western Siberian lapponica breeding populations but also central Siberian taymyrensis birds, that pass through in autumn to wintering areas in West Africa. The majority of overseas records have come from the Wadden Sea in spring and autumn, when birds have been on return passage to the breeding areas. There’s a 1996 summary of migratory movements of metal-ringed WWRG birds here:

The origins, moult, movements and changes in numbers of Bar-tailed Godwits Limosa lapponica on the Wash, England, Bird Study.  http://dx.doi.org/10.1080/00063659609460996 

Aivar Estonia

UV was spotted in Estonia in August 2012

By the end of 2015, 248 Bar-tailed Godwits had been colour-ringed and 92 of them seen again, many locally on the Wash. These high resighting rates are a consequence of focused searches by WWRG members and reports from birdwatchers submitting their records to sightings@wwrg.org.uk. Over the next few years it will be possible to estimate annual survival probabilities and to monitor how these change in the medium to long term. As was shown in the Yellow Sea, spotting a dramatic drop in colour-ring return rates provides evidence that development pressures are having an impact upon migratory species. Worsening conditions in the breeding grounds or wintering areas could well be detected through a more gradual but no less serious reduction in survival rates.


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

 

Lapwing moult

In most northern waders, post-breeding moult is a distinct phase – between autumn migration and the start of winter – but it’s different for Lapwings

Lapwing header

Primary moult is one of the key stages of a wader’s life. Knowing the length of the period in which birds are constrained by this energetic process may be really important to our understanding of the whole annual cycle of waders. In Oystercatchers, for instance, it has been shown that they cannot finish their primary moult in periods of low food abundance. One or more of the outer pairs of primaries are retained, becoming more faded and worn as the next twelve months pass and providing a signal of a previous period of stress. [See BTO report 238 by Atkinson et al.]

Lapwing in flight

The shape of a Lapwing’s wing is very different to that of most wader’s in the UK

Lapwing moult was first studied in detail in the 1970s using an innovative technique that did not require birds to be captured. By collecting primary feathers dropped by a flock of Lapwings that spent several weeks near their Buckinghamshire home, David and Barbara Snow were able to estimate the duration of moult. They did not start picking up feathers until August in 1974 but they were ready for the start of the 1975 season and captured a whole season’s worth of data that year, visiting the site every four days during a long, dry summer.

Primary wing moult

For flocks of waders in Britain and Ireland, autumn moult is generally squeezed in between their return from the arctic and sub-arctic breeding grounds and the start of winter, when days get shorter, the weather gets colder and much of the prey becomes less numerous and harder to access. In the late summer, adult birds start to discard the colourful feathers that they grew in spring and the main wing and tail feathers that have served them well for the best part of a year. The key period of moult is the time in which the ten primary feathers are replaced. The inner one (primary 1) on each wing is dropped first and the outer one is last. Each of the ten primary feathers is scored from 0 to 5, so an old wing has a score of 0 and a new wing has a score of 50. During the process, there is a gap in the wing, where new feathers are growing. A typical bird in mid-moult might have ten feathers scored as 5554332100 (moult score 28), with primary four nearly fully grown and primary eight newly discarded. Unsurprisingly, flight capacity is impeded. It’s not a great time to migrate – unless you happen to be a Lapwing.

David & Barbara Snow

Primaries

The primary feathers of a Lapwing are unusually distinctive

David & Barbara Snow were each respected ornithologists in their own right and David was the author of the BTO’s Guide to Moult in Birds and senior scientist in the bird section of what is now the Natural History Museum. Wherever they lived or worked – from Trinidad to Tring – they observed the birds around them, so when a flock of Lapwings gathered to moult near their home they decided to collect the feathers that they dropped. They discovered that it is possible to use the individual patterns of white spots and the lengths of primary feathers in order to assign primary number to discarded Lapwing feathers, and that this could be done with certainty for primaries 1, 2, 7 and 10 (with 1 being the innermost). Reference to a small sample of BTO moult cards allowed David & Barbara to assign moult scores of 1, 4, 29 and 41 to the points at which these four distinct feathers had been dropped and collected. The synchrony of moult in the two wings was evident: “Several times we found pairs of feathers lying exactly where they had been dropped, separated by a body width”.

Much of what the Snows discovered from recording in detail the feathers shed by their local flock of 70 and 120 moulting Lapwing in 1974 and 1975 is still relevant. They suggest that the collection of dropped feathers might be a useful adjunct to the study of moult in situations where birds roost in the same place on a daily basis, as might be the case for flocks of gulls or individual raptors.

David and Barbara also collected secondary feathers and tail feathers. As there is a difference between the outer tail feathers of adult and first-year birds they were able to show that early moulters included a higher proportion of first-year birds. The paper is well worth a read. David W. Snow & Barbara Snow (1976) Post-breeding Moult of the Lapwing, Bird Study, 23:2, 117-120

As far as I can ascertain, nobody has tried to use this technique again. I feel partially responsible, having written a follow-up paper with Clive Minton that pointed out some flaws in the methodology. These related to a lack of linearity in the progression of primary moult, as measured using the normal score of 0 to 50 based on 0-5 for the ten individual feathers, and the time taken to complete moult once the last primary has been dropped. Using data from Lapwing caught in cannon-net catches in the English Midlands, Clive Minton and I found that Lapwing moult starts very early, with median commencement and completion dates of about 7 June and 29 September – an estimated duration of 114 days and much longer than that suggested in the figure produced by the Snows. G. F. Appleton & C. D. T. Minton (1978) The primary moult of the Lapwing, Bird Study, 25:4, 253-256.

Lapwings are strange

Moulting Curlew

An August high-tide roost. Perhaps Curlew feathers could be collected at low tide?

Most waders that we see in the UK have distinct moult and migration phases to the post-breeding portion of their annual cycle.  After having successfully raised a brood of youngsters or attempted so to do, Turnstones, Bar-tailed Godwits, Knot etc. leave their nesting areas in the high Arctic and fly thousands of kilometres, arriving on our shores in July and August. Although some populations, such as most Dunlin of the schinzii race, only pause to fatten up and then move on to moult further south in northern Africa, many waders that use the UK during autumn undergo a full moult. One can imagine circumstances in which a small flock of inland-moulting Curlew that use the same roost site on a daily basis might be studied in the same way as the Snows studied their Buckinghamshire Lapwings, as long as the lengths and patterns on individual feathers allow the primary number of some of the individual primaries to be assigned with a degree of certainty.

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Lapwings were the first birds to be ringed in Britain & Ireland (in 1909). They appear in the logo of the BTO Ringing Scheme

Unlike most of their wader cousins, many Lapwings migrate while moulting their primary feathers. Arctic species have to make long-hop migrations and are restricted in their choice of feeding areas by the distribution of estuaries but Lapwings make short movements and can break their journeys as often as they like. The North Sea is the biggest barrier they face when making journeys from far east in Russia but a crossing from the Netherlands to Norfolk is less than 150 km. Lapwings arriving on the east coast of England have been seen to have gaps in their primaries, despite the fact that these feathers deliver most of the lift and propulsion.

Moult strategy is not the only strange thing about Lapwings; they have also been shown to exhibit abmigration, as described by Chris Mead in a paper with Jim Flegg and Chris Cox in 1968. Although most British-bred Lapwings return to their natal areas to breed, as shown by Pat Thompson et al in 1994, a small number of birds breed a long way from where they were hatched, including Russia, Norway and Sweden. The birds that go on to breed in continental Europe are assumed to join flocks which happen to be travelling east in spring. Given that British-hatched birds as old as 12 years of age have been found breeding in Russia, it is assumed that, having once travelled to a new breeding area, Lapwings will repeat the journey each year. Genetic mixing at large geographic scales would potentially explain a lack of morphological variation across the large range of the species.

Collect some feathers

Moult is currently only studied when birds have been caught but perhaps it might be possible to use digital photography to establish the primary moult duration of colour-ringed individuals or to use the Snows’ technique of collecting feathers from a moulting flock of birds over a period of a few weeks.  On an annual basis there may even be opportunities to monitor change?  A reduced rate of moult, as measured through the collection of discarded primaries, could provide a way to assess inter-annual variation in stress. I wonder if moult periods have increased for birds on the East-Asia Australia Flyway, where they are experiencing reductions in feeding opportunities on their southward migration via the Yellow Sea? Wouldn’t it be interesting if a technique first described by the Snows forty years ago could be used by a new generation of wader biologists when investigating the latest issues of conservation concern?


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

 

Oystercatchers: from shingle beach to roof-top

After over 150 years of successful exploitation of new breeding areas, there are signs that UK Oystercatchers are experiencing predation problems in the Scottish hills and facing disease-related issues on at least one Welsh estuary.

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Oystercatcher parents can fly off in search of food for chicks (Tómas Gunnarsson)

There are Oystercatchers flying over our Norfolk garden with worms to take back to their chicks, travelling up to a mile each way on feeding trips. This commuting behaviour opens up nesting opportunities not available to more conventional wader chicks which find food for themselves, albeit with some coaching. A pair of Oystercatchers can nest on the island of a former gravel pit and move up and down a river valley, to feed in wet grassland, pastures and arable fields, or hatch their chicks on the flat roof of a school and probe for worms on the playing fields. This flexibility has facilitated the spread of the species in England, and may be helping to compensate for declining numbers in the core breeding areas of Scotland.

A 150-year story of expansion

P1000520The Oystercatcher is a very distinctive and noisy bird. When pairs move into new areas they get noticed, providing us with a reliable history of their range expansion over the last two centuries. We might not now be surprised to see breeding pairs well inland, in lowland river valleys or on upland sheep pasture, but these were solely coastal breeders until about 1840, when the first pairs were recorded inland of the north Grampian coast. This nesting behaviour spread within Scotland and reached the English side of the Solway in about 1900 and Northumberland twenty years later.  You can read more in The Historical Atlas of Breeding Birds

The left-hand map below, from Bird Atlas 2007-11, illustrates the continuation of the expansion of the Oystercatcher breeding range between 1968-72, when the first few pairs had established themselves on gravel pits in the English Midlands, through to 2008-11, when pairs were well spread through English counties north of the M4. Oystercatchers have continued to colonise new counties; areas occupied over the last forty years are shown as red triangles, with larger ones being more recent.

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Maps of Oystercatcher breeding distribution from Bird Atlas 2007-11, which was a joint project between the Briitish Trust for Ornithology, BirdWatch Ireland and the Scottish Ornithologists’ Club

At first glance, all looks well. However, the right-hand map, which shows the change in abundance between the breeding season surveys of 1988-91 and 2008-11, tells a different story. Densities have been increasing in England (pink colours – darker means higher increase) but there have been major declines across much of Scotland (grey colours – darker means bigger drop).

websAlthough there has not been a large drop in the number of wintering Oystercatchers across the whole of the United Kingdom, the declining number of breeding birds in Scotland may well be to blame for the drop in winter Wetland Bird Survey (WeBS) counts for the country.  The graph alongside suggests that Scottish estuary counts are down by nearly 50% since the peak counts of 2002/03.

Breeding Season

oystercatcher

Schematic summary of migration of Oystercatchers ringed or recovered in Britain & Ireland, from Time to Fly by Jim Flegg (BTO)

Oystercatchers nest early in Britain and Ireland and most will have been on territory for several weeks by the end of March. At the same time, there can still be big flocks on the coasts. Some of these are young birds, which won’t breed until two or three years of age, but others will be adults that are fattening up in preparation for migrations to countries such as Iceland and Norway.  Oystercatchers breed beyond the Arctic Circle and all the way to the northern tip of both countries, where spring arrives several weeks later than it does in the UK.

Vero Oyc.jpg

Verónica Méndez-Aragon

When choosing a territory, a pair of Oystercatchers will look for food and somewhere to place a nest. The archetypal nest site might be on a beach, where the eggs blend in with the shingle that forms the nest cup, marine invertebrates can be collected from below the high tide-line and earthworms may be available on near-by fields, golf-courses or lawns, but the species has learnt to breed in a wide range of habitats.  When selecting somewhere to lay a clutch, usually of 2 to 3 eggs, a simple stretch of the imagination can turn the image of a beach into a river-bank, a gravel track or a bare patch in a field.

Ben Darvill

Three Oystercatcher chicks on the roof of The Cotterell Building at the University of Stirling (Ben Darvill / BTO Scotland)

Adding in a third dimension takes Oystercatchers to the flat roofs of buildings, such as those of Stirling University.  Here, all that lies between the fox-free shingle roof and worm-rich lawns below is a vertical drop for the chicks, when they are old enough. High-rise living is an international trait in Oystercatchers; one of the birds ringed in Norfolk by the Wash Wader Ringing Group nested in a window-box in Norway and the practice of roof-nesting is common in the Netherlands.

Oystercatchers look after their chicks for much longer than other wader parents.  Most wader chicks start finding their own insect food from day one, following their parents as they learn to pluck prey from the undersides of plant leaves or from the surface of mud and grass mosaics. Oystercatcher chicks expect a lot of their food to be brought to them. Roof-nesting chicks have no choice other than to wait for dinner to be delivered whilst those on the ground are able to do some of the work themselves.  Youngsters will beg for food for several weeks, even when they can fly, extending the parenting period beyond that which is normal for most waders. The team studying the changing migratory behavior of Icelandic Oystercatcher has found youngsters on mussel beds begging for food in October. (See Migratory Decisions for Icelandic Oystercatchers)

Population Trends

The Oystercatcher is an amber-listed species of conservation concern in the UK, to reflect the importance of these shores to the European breeding population of the species and their reliance outside the breeding season on a small number of estuaries. Although we know that individuals can live for up to 40 years, all is not completely rosy for the species, with predation and food supplies causing problems.

SAMPLED_5990014_300____As has been discussed in the recent Moorland Forum, ‘Understanding Predation report, declines in Oystercatcher numbers have occurred in some moorland parts of the range and there has been a drop in numbers of 29% across Scotland as a whole, since the start of the Breeding Bird Survey in 1995.  The English population had increased by 56% in the same period but this does not compensate for the numerically larger losses from the core northern areas. Local representatives and researchers who contributed to the Moorland Forum report highlighted crows, foxes, buzzards and ravens as the four main predators that threaten the success of breeding Oystercatchers.

Coastal food supplies are critical for Oystercatchers in the winter months and for at least the first two summers of a young bird’s life.  While they take a wide range of shellfish and worms, one of the key elements of the diet on many estuaries is cockles. In the past this has brought Oystercatchers into conflict with cockle fisheries. There was a major controversy in the 1970s when, at the behest of cockle fishers and despite the objection of conservationists in the UK and in Norway, permission was given to shoot 10,000 Oystercatchers on the Burry Inlet in South Wales – and embarrassment when cockle numbers continued to decline.

5-Cockle

These cockles have died very recently (image from CEFAS report)

The latest cockle problem is affecting both birds and people, again on the Burry Inlet but also in sites as far apart as the Dee, the Wash and the Dutch coast. Mass die-offs of young cockles are happening in most years, caused by three new parasites, first identified in Spain, America and Portugal, the worst of which causes the haplosporidian infection. In the five winters up until 1999/2000, the average peak count for Oystercatcher on the WeBS count on the Burry Inlet was 17,188, dropping in each of the next three periods to reach 12,195 in the five years up until 2014/15. This represents a 30% decline.

With no available treatments and with the parasites spreading into new areas, life could get tough for human cockle-gatherers and flocks of Oystercatchers, which rely on shellfish for their income and survival, respectively. You can read more about these issues in a CEFAS report which focuses on the Burry Inlet.

Summary: caring, spreading, declining and threatened by disease

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Unlike most wader parents, Oystercatchers find food to feed to their chicks (Tómas Gunnarsson)

  • Cockle die-offs have not as yet had a major, national population-level effect on wintering Oystercatchers but the presence of this threat to Oystercatchers and to other species that feed on young cockles, such as Knot and Turnstone, emphasises the need for continued monitoring and the value of WeBS counts.
  • Breeding Oystercatchers are in decline in the uplands and there is agreement that the role of predators in the moorland environment needs to be better understood. The Moorland Forum report mentioned above also focuses on four red-listed species: the near-threatened Curlew (see separate WaderTales blog), Lapwing, Grey Partridge and Black Grouse.
  • The Oystercatcher has been successfully expanding its breeding range and making use of new nesting opportunities for at least 150 years. Increases in England are, to some extent, compensating for declines in Scotland.
  • The fact that parents collect food for their young opens up breeding opportunities in areas where there are inadequate supplies of food adjacent to safe nesting sites. Clever birds!

This is a modified version of an article that first appeared in Shooting Times & Country magazine.


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

 

Are there costs to wearing a geolocator?

If you’re thinking of using geolocators to study bird migration then here’s a paper that you should read.

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Whimbrels on the move (Tómas Gunnarsson)

Devices attached to waders (shorebirds) are adding hugely to our understanding of their movements, and informing plans for the conservation of threatened species, but how safe are these devices for the individual birds that carry them? Emily Weiser and 49 coauthors have reviewed the available evidence in a recent paper Effects of geolocators on hatching success, return rates, breeding movements, and change in body mass in 16 species of Arctic-breeding shorebirds, published in Movement Ecology.

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Whimbrel wearing a geolocator (Camilo Carneiro)

Marking birds is not without cost. Catching a bird to fit a ring, however light and however expertly applied, subjects the individual to extra risk. Perhaps the ring might get wool tangled around it for instance? Logic suggests that every extra device, from colour-rings through to a harness that carries a satellite tag, adds mass and potential problems. This paper focuses on geolocators – the half-way house between satellite tags and colour-rings, in terms of weight. I find it encouraging that so many scientists have combined in this review of the way that geolocators affect birds’ lives. By providing their data for analysis, they remind us that professional ornithologists have a shared concern for the birds that they work on. As people, they want to minimise the effects on individual birds and, as scientists, they need to reassure themselves that tagged individuals are providing data that are representative of other birds of the same species.

What are geolocators?

Emily Weisser Semi

This Semipalmated Sandpiper carried a geolocator for two years (Emily Weiser)

Geolocators collect information on place and time. Unlike satellite tags, which can relay information from the bird to the scientist on a day-to-day basis, geolocators have to be deployed and then retrieved, so that data can be down-loaded. In the intervening period, these tiny devices record the time of dawn and dusk, information that can be decoded to reveal daily locations, apart from during the periods of spring and autumn equinoxes and if there is heavy cloud.  Geolocators are particularly useful for waders, as most of them live in very open environments (but less good for nocturnal species such as woodcock).

The data used in this paper relate to geolocators weighing between 0.8g and 2.0g, representing 0.1– 3.9 % of mean body mass of the species to which they were applied. They were attached to 16 species of migratory shorebirds, including five species with between 2 and 4 subspecies, making a total of 23 study taxa. The smallest species was only 26 grammes and the largest was just over a kilogramme. Birds were tagged at 23 breeding and eight nonbreeding sites, spread throughout the world.

Geolocators can be attached to harnesses and sit on the back of birds or, as in most cases studied here, attached to a ring or flag on a bird’s leg. The paper looks at the different effects of tags mounted in different ways.

Invaluable Data

Red-n-phal GFAMany wader populations are in trouble. Of the eight curlew species, for instance, one or two species are probably extinct, three others are endangered, vulnerable and near-threatened and only three are not causing concern

Establishing migratory routes and the timing of movements is a critical part of understanding the migration strategies of waders. The results collected from geolocators have important consequences for conservation and are truly fascinating. Who would have believed that Red-necked Phalaropes breeding in Shetland (north of Scotland and west of Norway) would migrate west and south to spend the winter on the surface of the Pacific Ocean between Galapagos and Ecuador? Geolocator tagging reveals Pacific migration of Red-necked Phalarope Phalaropus lobatus breeding in Scotland. Smith, M., Bolton, M., Okill, D.J., Summers, R.W., Ellis, P., Liechti, F. & Wilson, J.D. Ibis. DOI: 10.1111/ibi.12196

Waders operate at a truly global scale, with Bar-tailed Godwits making phenomenal journeys directly from Alaska to New Zealand. This species and others using the East Asian-Australasian flyway are causing major concerns for wader biologists, who have measured huge losses in populations wintering in Australia, New Zealand and south-east Asia. Ringing and colour-ringing had shown that birds fly north each spring to eastern Siberia and Alaska via the coast of eastern Asia – countries such as South Korea and China where there are major development pressures upon estuaries. Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Theunis Piersma,Tamar Lok, Ying Chen, Chris J Hassell, Hong-Yan Yang, Adrian Boyle, Matt Slaymaker, Ying-Chi Chan, David S Melville, Zheng-Wang Zhang, Zhijun Ma. Journal of Applied Ecology. DOI: 10.1111/1365-2664.12582

MUv116n2coverIdentifying key staging sites, such as the northern end of the Sakhalin peninsular, was possible thanks to the deployment of geolocators, as shown in this paper. Movement patterns of Sanderling (Calidris alba) in the East Asian–Australasian Flyway and a comparison of methods for identification of crucial areas for conservationSimeon Lisovski, Ken Gosbell, Maureen Christie, Bethany J. Hoye, Marcel Klaassen, Iain D. Stewart, Alice J. Taysom and Clive Minton. Emu. DOI 10.1071/MU15042

Using this information, conservation organisation and governments have started to work together to campaign for more sympathetic development of key areas. Conservation without borders – solutions to declines of migratory shorebirds in the East Asian–Australasian Flyway. Judit K. Szabo, Chi-Yeung Choi, Robert S. Clemens and Birgita Hansen. Emu. DOI 10.1071/MU15133

This is just one of many examples of the use of geolocators to fill gaps in migratory stories for waders. Geolocators are also being used to establish wintering areas for breeding species (e.g. Knot in South America) and to assess remotely whether individuals nest successfully. Using Geolocator data  to reveal incubation periods and breeding biology in Red Knots Calidris canutus rufa. Burger J, Niles L J, Porter R R & A D Dey. Wader Study. 119(1): 26–36.

Conclusions

It is not possible to reproduce all of the results in the paper here, or to list all the caveats presented by the authors, but these are the salient points. Anyone considering using geolocators on waders/shorebirds will want to read the whole paper in detail.

  • Importantly, no negative effects of geolocators were detected for most species of shorebirds – including some that migrate huge distances.
  • For some small-bodied taxa (mean body mass ≤58 g), there were substantial negative effects. Geolocators reduced nest success, hatching rate, and/or return rate for two small-bodied species – Semipalmated Sandpipers and Arcticola Dunlin.
  • Changing the way that a geolocator is mounted on the leg can have consequences in terms of return rates and damage to eggs. Simple changes, such as rounding the corners of flags may reduce problems.
  • Studies of the same species in different areas produced different results, in terms of the impacts of geolocators.
  • The findings suggest that guidelines for the relative mass of devices, as developed for backpack-style attachments, may be too liberal for leg-mounted tags. The graph presented in the paper suggests that negative effects may be detected when the tag and attachment together weigh more than 1.5% of body mass.
  • It is not unusual for a wader to live for more than ten years; the studies that contribute to this paper are mostly of short duration and cannot assess long-term effects of tags.
waders and spume TGG

Tómas Gunnarsson

To learn more please read the paper: The effects of geolocators on hatching success, return rates, breeding movements, and change in body mass in 16 species of Arctic-breeding shorebirdsEmily L. Weiser, Richard B. Lanctot, Stephen C. Brown, José A. Alves, Phil F. Battley, Rebecca Bentzen, Joël Bêty, Mary Anne Bishop, Megan Boldenow, Loïc Bollache, Bruce Casler, Maureen Christie, Jonathan T. Coleman, Jesse R. Conklin, Willow B. English, H. River Gates, Olivier Gilg, Marie-Andrée Giroux, Ken Gosbell, Chris Hassell, Jim Helmericks, Andrew Johnson, Borgný Katrínardóttir, Kari Koivula, Eunbi Kwon, Jean-Francois Lamarre, Johannes Lang, David B. Lank, Nicolas Lecomte, Joe Liebezeit, Vanessa Loverti, Laura McKinnon, Clive Minton, David Mizrahi, Erica Nol, Veli-Matti Pakanen, Johanna Perz, Ron Porter, Jennie Rausch, Jeroen Reneerkens, Nelli Rönkä, Sarah Saalfeld, Nathan Senner, Benoît Sittler, Paul A. Smith, Kristine Sowl, Audrey Taylor, David H. Ward, Stephen Yezerinac and Brett K. Sandercock. Movement Ecology 20164:12. DOI: 10.1186/s40462-016-0077-6

Implications

I am sure that members of panels charged with the task of issuing permits to those engaged in migration research will find this study tremendously useful, especially as so much detail has been made freely available within the paper and in supplementary material. It is hugely encouraging that, for most species, there is no evidence that the costs to individuals outweigh the potential conservation benefits. Future decisions to deploy devices on small-bodied shorebirds will be made on a case-by-case basis, weighing the potential impacts on individuals and populations against the value of improved knowledge of migratory movements.

BOU conference 2017

BOU confMost ornithological conferences now include talks that reveal new insights gained using geolocators or other devices carried by migrating birds. The spring 2017 BOU conference From avian tracking to population processes will aim to take this work one step further, by bringing together ornithologists and ecologists, in order to explore how tracking individuals can help to address questions about population processes and their implications for conservation and management.


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

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?

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

In a new paper in Wader Study, Tómas Gunnarsson and Guðmundur Guðmundsson have analysed the ringing recoveries of Icelandic Whimbrel and demonstrated that many probably make non-stop flights from Iceland to western Africa.  The study also helps 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.  The full paper is available to subscribers to Wader Study but a summary is available here.

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.

1 eldgos

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

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.

whimbrel-mig-fig1

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.

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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.

What next?

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Tómas Gunnarsson

This analysis of metal-ringed birds sets the context for new studies to understand the migration strategies of individual Icelandic birds, using geolocators and satellite tags. Hopefully we’ll soon know just how long these epic sea crossings from Iceland to Africa typically take, how migrants 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.


 GFA in Iceland

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

@grahamfappleton

 

Godwits in, Godwits out: springtime on the Washes

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

Graham Catley Welney

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

090601 N2568 limosa GW-WB Adm Cley-P

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 Daka

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

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

Limosa or Islandica?

subspecies.jpg

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

Ed Keeble G GO__W

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

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

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

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

Conservation importance for islandica

flock in air

Graham Catley

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

New hope for limosa breeding in the Ouse & Nene Washes

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Nene Washes RSPB reserve (RSPB)

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


 GFA in Iceland

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

@grahamfappleton

 

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. 

Cattle top adam cross

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

In a recent 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

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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.

CattleWorking 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?

Trampled egg christine tansey

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.

Redshank nest christine tansey

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

_DSC2219Redshank

Not quite long enough? Redshank nests are often completely hidden withing 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.

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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.


 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

 

 

All downhill for upland waders?

 

Are targeted payments for England’s upland farmers benefiting Curlew, Lapwing, Oystercatcher, Redshank and Snipe?

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The farmed land that fringes our moors provides important habitats for breeding waders (Dawn Balmer)

In the period 1995 to 2013, England lost 32% of its breeding Curlew, 31% of its Redshank, 27% of its Lapwing and 14% of its Snipe, according to the latest Breeding Bird Survey results. The uplands are the main stronghold for Curlew and hold (or used to hold?) significant numbers of the other three declining species. Is the story one of total gloom or are there areas where sensitive farm management and agri-environment payments are successfully supporting waders and other species associated with upland farms? A new survey, funded by Defra and coordinated by BTO aims to find some answers.

The snappily-titled Breeding Waders of English Upland Farmland survey starts in April and volunteers are still needed in many areas. Please visit the BTO website if you may be able to help.

More about the key species:

curle 004 (nest) (Derek Belsey) (A)

Derek Belsey

Curlew (recent 32% decline in England). The species is globally defined as near-threatened and has been added to the red list of conservation concern in the UK. Losses have been particularly severe in Ireland, Northern Ireland and Wales but the distribution is shrinking in England. There’s a WaderTales blog about Curlew here. Is the Curlew really ‘near-threatened’?

Lapwing (recent 27% decline in England). Most of the work to try to understand recent declines in Lapwing numbers has been undertaken on lowland wet grassland, where cooperative mobbing of predators is an important part of the daily routine for parents. In the uplands, where breeding densities are lower, it would not be surprising if predation pressures could be impeding species recovery. There are two WaderTales blogs about these issues. A helping hand for Lapwings and How well do Lapwings and Redshanks grow?

redsh 058 e (Jill Pakenham) (A)

Jill Pakenham

Redshank (recent 31% decline in England). The situation for Redshank is very similar to that for Lapwing, the presence of which may help in predator defence. There is a WaderTales blog about the special issues in the Uists (NW Scotland), where introduced hedgehogs are causing huge problems in this key wader hot-spot. Prickly problems for breeding waders

Snipe (recent 14% decline in England). The survey methods used in the new BWEUF survey are not designed to detect Snipe, which are mostly active at dusk, but the visits should provide useful count and distribution data for an under-researched species.

oyste 066 e (Nigel Clark) (A)

Nigel Clark

Oystercatcher (recent increase of 56% in England). Much of the increase may well be occurring in river valleys and newly created wetlands and gravel pits, rather than in the uplands. We know from the recent Moorland Forum report Understanding Predation that there have been changes in Oystercatcher abundance in much of upland Scotland between 1990 and 2010, potentially linked to predation pressure. It would not be surprising if similar processes operate in the English uplands.

How the BWEUF survey will work

Breeding wader populations in the UK have been a major conservation priority for some years. Declines continue despite the implementation of conservation measures that are designed to deliver appropriate habitats, some of which are supported through agri-environment schemes (AES). While enhanced monitoring of many upland and lowland habitats would be valuable, a particular gap is evident for in-bye farmland. This habitat can be defined as juncus/rush pastures, semi-improved pastures and meadows below the moorland line, although it technically includes all enclosed farmland. Using Defra funding, Natural England has commissioned BTO to run a volunteer-based survey, with RSPB field-staff filling gaps in less accessible areas.

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Photo: Dawn Balmer

This project will assess the importance of in-bye land for waders, by estimating the total numbers present in these habitats, relative to national estimates measured from Bird Atlas 2007-11 data. More importantly, it will set a baseline against which to measure future change in breeding numbers.  This will be used to assess the success of Environmental Stewardship management, as well as to measure differences in numbers between AES and non-scheme habitats for waders that nest and/or forage on in-bye farmland. The survey will use 2×2km grid squares (tetrads), as in Bird Atlas 2007-11. Volunteers are asked to make two morning visits to each tetrad, one between early April and mid-May and a second before mid-July, with a minimum of a two-week gap between visits. On each visit, volunteers will be asked to survey as many as possible of the fields in this in-bye buffer of 1km below the moorland line. They will walk to within 100m of every part of each field to which they have access, recording all birds seen and heard, noting any display or territorial behaviour and mapping the locations of target wader species.

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There’s an opportunity to record other species of conservation concer, such as this red-listed Yellow Wagtail (Jill Pakenham)

The key features of grassland management and structure, along with other land use, which dictate suitability for waders, will be recorded.  Predation has been identified as one potential driver of population decline – or an impediment to species recovery – so observers will be asked to record avian and non-avian predators.

Birdwatchers do not normally spend much time in this in-bye habitat so here’s an opportunity to capture as much information as possible, especially for any other waders and gamebirds (Black Grouse, Grey Partridge, Pheasant, and Red-legged Partridge). Valuable information can be data can be collected for Cuckoo, Linnet, Meadow Pipit, Reed Bunting, Ring Ouzel, Skylark, Stonechat, Twite, Wheatear, Whinchat and Yellow Wagtail, many of which are red-listed species of conservation concern (and bonus birds on a day’s birdwatching). To view further information on survey methodology follow this link.

In Summary

The wader declines quoted in this article use Breeding Bird Survey data from 1995 but there is evidence of longer-term falls for Curlew (55% since 1975), Lapwing (65%), Redshank (65%) and Snipe (90%). These are worrying numbers and it is to be hoped that the BTO can find enough volunteers for BWEUF, despite the fact that many of the survey squares are a long way from the flat-lands in which most English birdwatchers live. Curlews, Lapwings, Oystercatchers, Redshanks and Snipe are counting on us to count them.


 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

Spring moult in Black-tailed Godwits

Black-tailed Godwits will look and smell different by the end of May

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A spring flock of Black-tailed Godwits at Cley (Pat Wileman)

Before they return to Iceland in April or early May, wintering Black-tailed Godwits have got a lot of extra feeding to do, both to fuel their journeys north and to undertake a complete change of body feathers. The grey plumage that has protected them since the autumn is discarded, to be replaced by summer finery. Although more colourful, these feathers provide cryptic camouflage in the habitats in which the birds nest – and they have less odour too.

There is a lot of individual variation but the timing of the spring moult of Icelandic Black-taileGodwits seems to differ depending on the wintering area used by individuals. Many Icelandic birds that enjoy the sun in Portugal, for instance, can start to change colour before the turn of the year, but there is little red to be seen in British flocks until February or even March. We have the impression that there might be enough variation across Britain & Ireland to potentially pick up differences at this scale but we have yet to establish if this is true.

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Full summer plumage in Iceland (Tómas Gunnarsson)

Some godwit observers have been scoring the moult of spring flocks of Black-tailed Godwits for years, especially for ringed individuals. This has given us quite a lot of data from a few sites, but spread over a number of years and a range of spring conditions. We think that we may be able to look at the regional differences more effectively if we can collect images from as many flocks as possible over one weekend. We chose Easter weekend, Fri 25 to Mon 28 March to try this out, as we thought that this should give us as much variation as possible, with birds at several different stages of moult. Birds are scored from 1 (full winter) to 7 (full summer) according to the table below and images at the bottom of the blog but all we needed was pictures from birdwatchers that we could then score. We had not reckoned on Storm Katie!

moult tableThis is very much a pilot project. We know that we can score most birds when they are seen moving around, so that each bird gives a view of chest side and back. Can we capture this information from a sample of birds in two-dimensional pictures? If this works, potentially we can run a season-long project next spring.

Spring moult

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Cameras at the ready (Graham Catley)

There is a big difference between the winter and summer plumage of Black-tailed Godwits. Over the course of a few weeks a grey individual turns into a thing of beauty. Camera shutters start to click in bird hides when a flock of birds sweeps back and forth, flashing white as the sun shines on bellies and underwings and then russet red as it catches their backs. It would be easy to think that these summer colours make Black-tailed Godwits more obvious, when they are nesting, but that’s not the case. In rusty-orange sedge-edged pools and when creeping their way through the red stems of dwarf willow on their way to a carefully hidden nest, they are very well camouflaged.

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Plumage 6 (left) and 5 (right). Photo: Dennis Swaby

Most wading birds moult into a summer plumage in spring. For Black-tailed Godwits, this process involves body feathers, some of the small coverts on the wings, scapulars and a variable number of tertials. Their individuality is apparent from the richness of colour, the mixture of red, black and white feathers in the body and of grey and red feathers in the back. When the moult has been completed, male birds tend to be redder in the chest and neck and they have fewer grey feathers in the back than females, but there is an overlap. When sexing methods were checked against DNA samples it was shown that experienced observers could correctly assign sex to 82% of marked breeding birds in the field for which the sex was also determined by DNA. There’s an interesting paper about this in Bird Study. 

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By mid-April Black-tailed Godwits in the UK are in virtually full summer plumage (Graham Catley)

Breeding waders don’t just look different – it has been suggested that they smell different too. Birds of a range of species, including Black-tailed Godwits, have been shown to produce a different preen gland oil with which to groom their summer plumage feathers, with monoesters replaced by diesters as winter feathers are discarded and pre-nuptial moult progresses. This was something that was first shown for Knot by Jerooen Renerkeens and colleagues and then for another eighteen species, breeding in both high Arctic and temperate conditions. In nesting birds, secretion of diester waxes continues through to egg-hatching, with the lowest occurrence of diester production in male Ruff and male Curlew Sandpipers. Given that these are the only two groups of birds in the sample under consideration that don’t incubate eggs, Jeroen et al suggest that diester preen waxes are harder for predators to detect using a sense of smell. You can read more here.

Here’s a reminder of the survey protocol

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This plumage 3 bird will soon be a plumage 4 – lots of new feathers are growing through on the breast (Pat Wileman)

Photographers were askd to find a flock of Black-tailed Godwits over the Easter weekend 25-28 March and to take one or more pictures of a representative portion of the flock. A picture of between 50 and 100 birds should give us between 25 and 50 birds to score. We need to see the chest and back of each individual so feeding birds are more easily scored than densely packed roosting birds. Ideally, birds will be half way between in-profile and head-on. Birds in shadow are harder to score so having the light behind you would help.

Please send any remaining photographs to godwitmoultphotos@gmail.com. It would help if you could label each image to include the site, date and name (e.g. Welney120316Appleton). Add a number at the end if sending more than one image. Please continue to send colour-ring sightings to the usual e-mail addresses.

Any help will be very much appreciated. No photograph will be reproduced without permission.

Scoring Black-tailed Godwit moult

Your pictures will be used to score moult, according to the levels in the table above. Here are some samples:

better moult


 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

 

 

Why do Turnstones eat chips?

Turnstones feeding on discarded chips in Hunstanton – a sign of desperation or just opportunism?

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Turnstones feeding with Starlings and Collared Doves at Port Sutton Bridge (Allison Kew)

I can think of three good reasons to worry about Turnstones wintering in the UK and a couple of arguments to suggest that that the species will cope – whatever problems they might encounter.  On the negative side, numbers have dropped by 50% in just thirty years, they breed on the most northerly (and hence climate-sensitive) bit of available land in the northern hemisphere and we frequently see them scavenging on unnatural foods, such as discarded take-aways.  On the plus side, Turnstones are long-lived birds that will eat almost anything.

Tough waders

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From Time to Fly, by Jim Flegg (BTO)

The Turnstones we see around the shores of the British Isles in the winter are almost all from Greenland and the Canadian Arctic (green arrows on map). There’s a hint, in the BTO’s Migration Atlas, that east coast birds are more likely to have bred in eastern Greenland, whilst birds from western Britain tend to head further west, to arctic islands such as Ellesmere. A few Scandinavian breeders may winter here but these birds mostly turn up on spring and autumn passage (orange arrows on map).

In a 1985 paper in Bird Study, Neil Metcalfe and Bob Furness showed that 95% of Turnstone colour-ringed on the Clyde arrived back there after the breeding season, having undertaken two Atlantic crossings and bred in the High Arctic. Perhaps unsurprisingly, given this high survival rate, the BTO longevity record is over 20 years. This is higher than that for any other Turnstone ringed (or banded) as part of a European or American ringing scheme, but this record may well increase still further, now that birds wear harder, longer-lasting rings.

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Checking to see what the tide has washed up (Graham Catley)

One way Turnstones can survive is to eat other birds, as we found in the winter of 1990/91, when nearly 5000 waders were found dead in south-east Britain, after a period of particularly cold weather. Although 2442 Redshank, 1357 Dunlin, 501 Grey Plover, 149 Knot, 139 Oystercatcher and 90 Curlew corpses were found on the tide-line, there were very few reports of dead Turnstones. Some of those that were still to be found on beaches were feeding on the bodies of other waders. (Further details in Clark, J.A., MPhil Effects of severe weather on wintering waders, University of East Anglia, 2002)

Turnstones are physically tough too. On one night in James Bay, Canada, I accidentally ran over one on a beach when driving a three-wheel ATV motor-bike. It was under the tyre (and me) before I had time to spot it. I stopped and picked the gravel out of its feathers and it flew off, apparently none the worse for the encounter.

Dinner is served

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There’s not much of a jump from scavenging for fish bits on a jetty to waiting for chips outside a fish & chip shop (Graham Catley)

As a species, Turnstones are remarkably adaptable when it comes to their choice of food outside of the breeding season. They can be found on the most exposed of shores (feeding in breaking waves along with Purple Sandpipers), on the flat sands of estuaries (perhaps in shellfish beds with Oystercatchers), or on the receding tideline with Sanderling. Colour-ringing tells us that individuals adapt to particular feeding areas, whether these be Scottish rock-pools or under bar-tables on beaches in the Caribbean. If opportunities arise they take them – when high tides wash maggots out of seaweed beds, when cockle diggers have been disturbing cockle beds, if storms throw up shellfish onto the tideline or if a carcase washes up on a beach. There’s even an oft-quoted example of Turnstones feeding on a human corpse (Mercer, A. J. 1966. ‘Turnstones feeding on human corpse’. Brit. Birds, 59: 307). 

Numbers

The latest winter population estimate for the UK is 51,000 Turnstones with about 20,000 of these on estuaries and the rest on the open coast-line. The species is only amber-listed on the latest UK Birds of Conservation Concern list, based on a decline of 20-30% in the 25-year period under consideration.

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59% of UK Turnstone were found on open shores during the NEWS-II survey

According to the latest Wetland Bird Survey data, the UK population in 2013/14 was about the same as during the period 1974 to 1983 but, in the intervening years, numbers have risen steeply and then fallen again. Were the chosen window for conservation-listing to be 1987/88 through to 2013/14, the decline would be about 50% and the species might have been red-listed. Internationally, the Ruddy Turnstone is of ‘least concern’, when assessed against BirdLife International criteria, reflecting a wide distribution, large population and relatively shallow decline in numbers.

Given that the current trend in Turnstone numbers is very much downwards, perhaps the species should be receiving a bit more attention?

That’s a strange place to find Turnstones?

When bird species are in trouble they tend to turn up in odd places – Barn Owls hunting along roads in snowy weather, for instance – but sometimes the ‘go to’ food becomes a favourite – as we saw when Siskins started homing in on bird feeders. Turnstones are commonly found foraging in non-tidal situations and a neat paper by Jennifer Smart and Jennifer Gill aimed to work out whether they are forced to do this or they’re there because these are good options.

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Catching Turnstones at dawn on the brick-weave of the dock required some lateral thinking. Note the sand bags used to make emplacements for the cannon (Allison Kew)

A flock of Turnstone on the Wash (eastern England) was first noticed feeding on the dock-side at Sutton Bridge in 1998. Over the next few winters, these birds provided an opportunity to try to work out whether this behaviour was a consequence of poor food supplies on traditional feeding areas or just opportunism. In their introduction to the paper in Biological Conservation, arising from this work, Jennifer Smart and Jennifer Gill said “Many species of shorebird typically forage almost exclusively on intertidal habitats. When such strongly maritime species choose to forage on non-intertidal habitats, it may either be a response to deteriorating intertidal conditions or to the discovery of more profitable resources in non-intertidal areas. Methods which allow distinction between these two will clearly be important for identifying problems in intertidal habitats”.

Smart, J. & Gill, J.A. (2003) Non-intertidal habitat use by shorebirds: a reflection of inadequate intertidal resources? Biological Conservation, 111, 359369.

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Turnstones feeding on grain and fish-meal: Allison Kew

Port Sutton Bridge is a four-berth facility on the canalised River Nene, four kilometres inland of the Wash. Although it handles a variety of cargo, the two that interest Turnstones are grain and fish-meal, quantities of which are spilt on the dock and presumably in the water. By colour-ringing individuals, using cannon netting techniques that had to be specifically adapted by the Wash Wader Ringing Group for the purpose, and counting birds at different stages of the tide, in a variety of weather conditions and over the course of the non-breeding season, Jen Smart aimed to understand how individuals were using the site.

Turnstone had first been observed using Port Sutton Bridge in January 1998, when a flock of 196 birds was present, grain exports having commenced at the port ten years earlier. In the period of the study (1997-2002) the maximum count was 576, a significant proportion of the estimated turnstone population of 600 on the Wash, according to Wetland Bird Survey data, although the Turnstones’ habit of roosting on offshore buoys over high tide (when counts take place) may make this WeBS total a slight underestimate.

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Colour-rings were used to measure turn-over. Ten birds were also radio-tagged. All 9 adults split their time between mud-flats and the port area but the one juvenile was only ever recorded in or around the port (Jen Smart).

Turnstones did not head straight for the port when they returned from Greenland and Canada. Very few fed there in the period July to December and, when they did start to use the site, large numbers generally only occurred at high tide, when other food sources were unavailable, and on colder days, when the availability of invertebrates on mudflats is often reduced and energetic demands are likely to be higher. The numbers and timing indicated that the switch to the dockside arose because the non-intertidal habitats were being used to supplement the diet on the preferred intertidal mudflats.

Jen Smart spent a lot of time watching Turnstones feed at the port, collecting their droppings and sampling the food available. In the paper she clearly shows that there was more than enough food for the whole Wash population on most days, so most birds were actively choosing not to make full use of the resources available most of the time. This could have been because of disturbance on the site (although the birds tolerated people) but was more likely to be realated to actual or perceived predation risk, and the lower quality of the foods available.

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Three Canadian-ringed bird were observed at Sutton Bridge. This one spent several winters in Cleethorpes, Lincolnshire (Chris Atkin)

Given that grain has a low fat content and there are high risks of predation and disturbance associated with the site, why did Turnstones choose to forage there? One possibility is that declining shellfish stocks on the Wash forced the birds to exploit alternative food sources. Within faecal samples collected on the dock, the commonest intertidal prey remains were shells of young cockles, although hard-bodied prey such as these will be more prevalent in faecal remains than soft-bodied prey. This strongly suggests that grain and fishmeal were acting as a ‘top up’. Interestingly, when there was a heavy fall of cockle spat in 2000 there was a reduction in numbers of Turnstone at the port in the next winter.

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Three colour-ringed Turnstones at Heacham, 20km from Sutton Bridge (Jen Smart)

By looking at the pattern of counts, Jen Smart & Jenny Gill could infer that the port is a source of supplementary food and not a preferred resource. This allowed them to suggest that Turnstones may have been reacting to declines in intertidal prey that also affected other shorebird species on the Wash over the same period. The availability of wheat grain at Port Sutton Bridge, in addition to field and river edge habitats, appeared to have been playing a highly significant role in maintaining the internationally important status of Turnstone on the Wash. In this study, scientists were able to assess the likely cause of the habitat switch before any decline in the Turnstone population had taken place.

Implications

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Showing off a full set of 5 colour-rings (Richard Chandler)

The invertebrate populations of intertidal mudflats in NW Europe are currently threatened by sea level rise, development pressures, disease, exploitation of shell fisheries and climate changes which can alter the suitability of the habitat for particular species. The impact of these processes is often unclear because long-term, broad-scale data on intertidal invertebrate populations are rare. Changes in the distribution or species such as Turnstone, Redshank and Oystercatchers, all of which are known to switch to terrestrial habitats, may therefore often be the first indication of pressures on bird populations that have been caused by a decline in invertebrate abundance. These changes in local bird numbers can be picked up because there are regular counts of waders on estuaries, particularly by birdwatchers contributing to the Wetland Bird Survey and the associated Low Tide Counts.

Desperation or Opportunism?

So, should we be worried if we see Turnstones outside a fish & chip shop? I guess that, once an individual Turnstone has discovered that there’s an easy source of extra food on a Norfolk sea-front or under the tables of a beach bar in the Caribbean, then it’s probably going to continue to exploit these opportunities. On the other hand, if the flock is getting bigger then perhaps we should ask “why?”

Smart, J. & Gill, J.A. (2003) Non-intertidal habitat use by shorebirds: a reflection of inadequate intertidal resources? Biological Conservation, 111, 359369.


 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.

@grahamfapppleton