Why count shorebirds? A tale from Portugal

The Sado Estuary is one of Portugal’s most important wetlands – a key link in the chain of sites connecting Africa and the Arctic, on the East Atlantic Flyway. In a paper in Waterbirds, João Belo and colleagues analyse changes in numbers of waders wintering in this estuary over the period 2010 to 2019, with a focus on roost sites. These results are interpreted in regional and flyway contexts. The team find serious declines in numbers of Avocet, Dunlin and Ringed Plover.

Lost roost sites

The Sado Estuary became a nature reserve in 1980 and has since been classified as a Ramsar Site, a Special Protection Area (SPA – Natura 2000) and an Important Bird and Biodiversity Area. The Estuary lies about 30 km south of the much larger and more famous Tagus (or Tejo) Estuary, which is threatened by a new international airport (see Tagus Estuary: for birds or planes?). A suggestion that the Sado could provide mitigation habitat for damage done to the Tagus prompted scientists from the Universities of Aveiro and Lisbon to review the current state of the estuary.

João Belo and his colleagues used monthly data from a programme of wader surveys, conducted largely by volunteer birdwatchers. These took place between January 2010 and December 2019. Roosting birds were counted at high tide along the northern shores of the Sado estuary and any habitat changes were noted.

During the ten-year survey period, 21% of the available high-tide roost area was lost. These changes were associated with the commercial  abandonment of saltpans (with consequent increases in vegetation) and the conversion of others for fish farming (often with netting, to keep out fish-eating birds).

Results of the survey

In their paper, João Belo and colleagues focused on total numbers of waders and counts of the six most commonly-encountered species: Avocet, Dunlin, Black-tailed Godwit, Redshank, Ringed Plover and Grey Plover. They compared winter (Dec, Jan and Feb) counts in 2019 with those from 2010. This is when peak numbers of Avocet, Redshank and Grey Plover occur. Higher counts of Dunlin are made in spring, as schinzii birds returned from Africa, with peak counts of Black-tailed Godwit and Ringed Plover occurring in autumn.

The key findings are:

Ringed Plover numbers dropped by 23%

• There was a strong decrease in the overall number of waders wintering in the Sado Estuary. This trend is mostly driven by steep declines in three of the six most abundant species: Avocet, Dunlin and Ringed Plover.
• Avocet numbers were 42% lower in 2019 than they had been in 2010.
• Dunlin numbers dropped by over half, with 2019 counts being only 47% of those in 2010. These are mostly dunlin of the alpina subspeciesthat breed between Northern Scandinavia and Siberia.
• Ringed Plover numbers dropped by 23% between 2010 and 2019.
• Redshank increased significantly between 2010 and 2019, while the population of Grey Plover was relatively stable, and it was not possible to derive a population trend for Black-tailed Godwit.

It is interesting to look at these patterns alongside data collected in Britain & Ireland, over the same period. As discussed in Do population estimates matter? and Ireland’s wintering waders, there have been major changes in wader numbers, with most species currently in decline.

At the same time that Avocet numbers have dropped on the Sado Estuary they have rocketed in the UK (here seen on the Humber Estuary)

• Winter Avocet numbers have increased massively in Britain & Ireland. It is possible that young birds are more easily able to settle in these northern areas, now that winter temperatures are generally warmer. Declines in Portugal may reflect a northwards shift of the winter population, driven by new generations of birds.
• Numbers of Ringed Plovers in Britain & Ireland did not change over the period 2010 to 2019 but had dropped a lot in the preceding twenty years.
• For Dunlin, the size of the declines in Britain & Ireland are consistent with those on the Sado. It has been suggested that more young birds might be settling in areas such as the Wadden Sea, closer to Siberian breeding areas, something that may have become more possible given the reduced intensity and occurrence of freezing conditions along the east coast of the North Sea.

Regional and Flyway patterns

As discussed in the blog Interpreting changing wader counts, based on research led by Verónica Méndez, local changes in numbers are usually reflective of broader changes in population levels. Individual waders are unlikely to seek alternative wintering sites unless habitat is removed, so birds do not re-assort themselves into the ‘best’ areas when population levels decrease. Instead, there is general thinning out across all sites as populations decline. In this context, it is unsurprising that the trends in the Sado Estuary are similar to those found elsewhere in Portugal and in other Western European wintering areas.

Looking forwards

The survey data collected between 2010 and 2019 form a useful backdrop against which to monitor what might happen when (or perhaps if) a new international airport is constructed within the nearby Tagus Estuary. If some birds are displaced to the Sado, increases in numbers might be expected.

Displacement is not cost-free, as has been shown in a well-studied population of Redshanks on the Severn Estuary in Wales. When Cardiff Bay was permanently flooded, as part of a major redevelopment, colour-marked Redshank dispersed to sites up to 19 km away. Adult birds that moved to new sites had difficulty maintaining body condition in the first winter following the closure of Cardiff Bay, unlike the Redshank that were already living in these sites. Their survival rates in subsequent winters continued to be lower than for ‘local’ birds, indicating longer-term effects than might have been predicted.

These three papers are essential reading for anyone interested in the consequences of displacements caused by development projects.

• Burton, N.H.K. 2000. Winter site-fidelity and survival of Redshank at Cardiff, South Wales. Bird Study 47: 102–112.
• Burton, N.H.K. & Armitage, M.J.S. 2005. Differences in the diurnal and nocturnal use of intertidal feeding grounds by Redshank. Bird Study 52: 120-128.
• Burton, N.H.K., Rehfisch, M.M., Clark, N.A. & Dodd, S.G. 2006. Impacts of sudden winter habitat loss on the body condition and survival of Redshank. Journal of Applied Ecology 43: 464-473

Given that the Sado has multiple conservation designations, including as a Ramsar site, and that this study has shown a clear loss of available roosting areas, perhaps it is time to identify a high-tide refuge that can be fully protected and managed in ways which create a range of suitable habitats for use by long-legged and short-legged waders. A nature reserve such as this has a potential to attract birdwatchers too, with prospective increased income from tourism.

Sado International

Curlews don’t get a mention in this paper but the The Sado provides a neat link to a 2022 blog, A Norfolk Curlew’s Summer. This tale focuses on ‘Bowie’, a male Curlew that breeds in Breckland (Eastern England) and has been tracked to The Sado Estuary. In the blog, Bowie’s story stops in The Tagus but he subsequently headed further south to The Sado, where he spent the winter. At the time of writing (13 Feb 2023) he is still there but hopefully he will heading north soon.

The Sado is not only important in the winter, of course. As mentioned earlier, it is a spring stop-over for birds such as schinzii Dunlin, heading north from Africa to Siberia, and a moulting/staging site for waders heading south in late summer. Tracking and colour-ringing are telling more of these stories, with links to countries as far north as Canada and Siberia and as far south as South Africa.

The overgrown embankments within the former saltpans no longer provide suitable roosting sites for waders

Keep counting

The Sado story could not have been written without the work of volunteer counters who collect monthly data during the winter months, on the Sado Estuary, across Portugal and on the wider East Atlantic Flyway. These monitoring efforts are essential when attempting to track changes in wader populations, especially when extra information can indicate links to habitat changes, as is the case in the Sado. The international picture is painted using Flyway information generated using January counts that are developed by the Institute for Nature Conservation and Forests (ICNF).

Here is a link to the paper:

Synchronous declines of wintering waders and high-tide roost area in a temperate estuary: results of a 10-year monitoring programme. João R. Belo, Maria P. Dias, João Jara, Amélia Almeida, Frederico Morais, Carlos Silva, Joaquim Valadeiro & José A. Alves. Waterbirds. doi.org/10.1675/063.045.0204

Birdwatchers that volunteered to survey roost-sites gather for a team photo

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

In amongst the tidewrack

Double-banded Plover

Tidewrack has an image problem. Who wants to see a dark line of seaweed on a beach of white sand or to smell rotting beds of kelp in enclosed bays? Shorebird conservationists may understand the feeding opportunities that are provided by fresh and older seaweed but, for tourist boards, tidewrack is something that needs to be cleared away.

It turns out that tidewrack is not just a biodiverse habitat; the mere presence of seaweed creates spaces in which waders can roost and find shelter. In a paper in the Journal of Applied Ecology, Timothy Davis & Gunnar Keppel get down to Turnstone-level, to investigate the important microhabitats within different forms of beach-cast wrack.

An Australian autumn

Readers in the northern hemisphere may well have seen wintering waders sheltering in the lee of clumps of tidewrack, as a gale blows snow and sand across a beach. At Danger Point, about half-way between Melbourne and Adelaide on the coast of Australia, conditions are somewhat different, with December and January temperatures topping 30°C, conditions in which waders must try to avoid over-heating. By April, when the Davis & Keppel study was carried out, conditions were autumnal, with cool mornings. Three of the species that might be seen on a European beach were present – Turnstone, Sanderling and Bar-tailed Godwit – but with the addition of Curlew Sandpipers and Red-necked Stints, that were about to depart for Siberia, and Double-banded Plovers that breed in New Zealand.

Which looks best – a barren beach or one strewn with seaweed?

What might waders be looking for?

Red-necked Stints

The research team was interested in the range of microclimates available on beaches with beach-cast wrack, to investigate the link between microclimates and microhabitats and how they are used  by waders. They expected to find warmer temperatures and higher humidity on aged wrack, due to advanced decomposition, and ameliorated conditions where wrack deposits provided shelter from prevailing winds. They predicted that waders would use microclimates that could reduce energy loss.

Observations

Data on temperature and humidity were collected by creating miniature Stevenson Screens – hollow white practice golf balls with iButtons inside them, attached to short bamboo canes, so as to be 10 cm above the substrate surface. If interested in conducting this sort of study, it would be sensible to read the methods section of the paper. Sample points were on bare sand, in areas with fresh wrack deposited on the sand and in beds of old tidewrack. Based on surrounding features and observations of prevailing winds, sample points were classified as sheltered or exposed.

Instantaneous scan sampling was used to classify migratory shorebird behaviour for the entire Danger Point study area (i.e., the area over which the microsensors were placed) at 15 min intervals on four days during April, as birds were preparing to migrate. Birds were classified as roosting (loafing, sleeping or preening) or as foraging on one of the three substrate types.

Variability of microclimate

As expected, there were significant differences among the three substrates (sand, fresh wrack and aged wrack) for mean, maximum and minimum temperature and absolute humidity. The temperature above the surface of aged wrack was consistently higher than elsewhere, with one notable exception: in the early mornings, when newly deposited seaweed retained some of the heat from the warmer ocean, temperatures were warmer on fresh wrack than on sand and aged wrack. For aged wrack, humidity was highest above deeper beds.

Curlew Sandpipers on the tide-edge

Bird Behaviour

Six species of wader were studied and included in ‘all waders’ counts but there were insufficient sightings of Bar-tailed Godwit, Curlew Sandpiper, Ruddy Turnstone and Sanderling for separate analyses. The main focus was upon Red-necked Stint (64.0% of observations) and Double-banded Plover (31.4%).

Double-banded Plover sheltered by tidewrack

• Roosting birds were recorded on aged wrack 16 times more frequently than sand, and three times more than on fresh wrack.
• Foraging birds were observed more than four times as often on aged wrack, when compared to fresh wrack or sand.
• However, roosting on fresh wrack was more frequent in cooler, early-morning temperatures, for all waders and for the Double-banded Plover, when considered separately. Neither temperature nor absolute humidity were significant predictors of the proportion of Red-necked Stints roosting in areas with fresh wrack.
• Foraging by waders (in general) and Double-banded Plover (in particular) was also more common within fresh deposits of wrack when temperatures were low and particularly if humidity was high. For Red-necked Stint, temperature alone predicted whether they were more likely to feed on fresh wrack, rather than aged wrack.

The importance of microhabitats

The authors show that sandy beaches with beach-cast wrack provide a complex mosaic of microclimates/habitats across differing substrates. Birds seem to exploit the microclimatic variation by using microhabitats that minimise energy expenditure, as both foraging and roosting were most likely to occur on the substrate providing the warmest, most energy-efficient conditions at the time.

There is well-documented evidence that food availability increases as seaweed decays, because wrack-beds provide homes for invertebrates, particularly developing larvae. This explains a predominance of foraging on aged wrack, which is likely to provide the best feeding opportunities. The key finding in this study is that tidewrack on sandy beaches provides important additional benefits for waders, by providing shelter and warmth. This may be particularly important when birds are fattening up for the next leg of a migratory journey. It is particularly interesting that, early in the morning, Double-banded Plovers and Red-necked Stints foraged within fresh wrack, the warmest available substrate at that time. Perhaps the effect of microclimate (temperature, humidity & shelter) might be usefully studied in other circumstances in which waders feed and roost?

The bigger picture

Turnstone, Sanderling, Purple Sandpipers and Dunlin on an Icelandic beach, having just crossed the Atlantic

When considering the role that coastal ecosystems play in the lives of waders, the main conservation focus has been on estuaries, as for instance discussed in Wader declines in the shrinking Yellow Sea. The open coastline is under threat too, squeezed by rising sea levels, battered by more frequent storms, polluted by plastic etc. In some areas, waders that use these habitats outside the breeding season are also prone to human (and canine) disturbance, as described in this Turnstone study.

Alongside more general habitat degradation, there are specific threats to tidewrack habitats along the coastline. This starts offshore, with the harvesting of stands of growing kelp, and continues when fresh tide-wrack is collected or cleared from shorelines. In 2018, it is estimated that 15,000,000 tonnes of brown algae were removed, globally. Traditionally, rotted tidewrack has been used as a fertiliser on nearby fields but most of the current output is collected when fresh and used to produce alginates, for food manufacture and biomedical purposes. Increasingly, attention is turning to use in biofuels, which has the potential to greatly increase the demand for seaweed.

Ringed Plovers in amongst seaweed on a Northumberland beach (UK)

Whilst the food, biomedical and energy industries see value in tidewrack, the tourist industry appears to see it as an untidy nuisance that spoils the image of a pristine beach. Who knows how much tidewrack is removed from beaches during daily grooming sessions or dug out of wader-rich corners before the start of the tourist season? If the image of what constitutes a welcoming beach is to be changed then perhaps there needs to be a focus on the interest that seaweed adds to a tideline walk – as visitors collect shells and look for amber, sea-coal and egg-cases. Is this naïve; have cotton buds, bottles and plastic sullied the image of tidewrack? Should we share more photographs of Sanderling chasing through seaweed-flecked spume and flocks of waders ‘chilling’ on banks of beautifully lit seaweed, instead of the barren white beaches that are used in holiday adverts?

As Timothy Davis and Gunnar Keppel conclude: “Beach-cast wrack created a complex mosaic of unique microclimates varying in space and time, which seemingly allowed shorebirds to minimize energy expenditure, by selecting the thermally most favourable habitats for roosting and foraging. Removal of beach-cast wrack therefore reduces habitat quality and increases energy expenditure and resources in shorebirds and may contribute to the observed decline of migratory shorebird species globally. Management of coastal ecosystems and shorebirds therefore needs to maintain fine-scale environmental heterogeneity.”

Paper

Fine-scale environmental heterogeneity is important for conservation management: beach-cast wrack creates important microhabitats for thermoregulation in shorebirds. Timothy John Davis & Gunnar Keppel. Journal of Applied Ecology. April 2021

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

Disturbed Turnstones

In a 2020 paper, Mark Whittingham and colleagues show that, in one area of northeast England, the decline in Turnstone numbers is more obvious on mainland sites that are subject to human disturbance than on offshore refuges. Whilst national declines are probably linked to factors affecting productivity in breeding areas in Greenland and Canada, it is interesting that Turnstone seem to be withdrawing into areas where they are subject to less winter disturbance.

Turnstones – some background

The Turnstones that we see around the coastline of Britain and Ireland in the winter are almost exclusively birds that fly here from Greenland and eastern Canada, as you can read in this blog about wader migration (Which wader, when and why?). Britain’s wintering Turnstone numbers are falling, as are populations of several other species, such as Curlew, Oystercatcher, Knot and Redshank (see Do population estimates matter?). Turnstones are opportunist feeders; although traditionally thought of as rocky coast specialists, they can also be found on muddy estuaries and around beach-bars in the Caribbean (Why do Turnstones eat chips?).

Measuring disturbance

Assessing the effects of disturbance during the winter is not easy. Feeding waders may be flushed by bait-diggers, kayakers, dog-walkers etc. but is this an issue if the food that they were attempting to eat becomes available later? To demonstrate that disturbance is a real problem, one would ideally demonstrate reductions in fitness measures such as survival, recruitment and/or productivity. This is discussed in a paper by Jenny Gill and colleagues, who studied the potential effects of disturbance on feeding Black-tailed Godwits (paper in Journal of Applied Ecology) and in another paper by Colin Beale and Pat Monaghan that shows that well-fed Turnstones were quicker to respond to disturbance than birds that had not received supplementary food supplies (Animal Behaviour).  Birds may be quicker to fly if they are well-fed or there is somewhere else where they can feed. The ones that have no choice and are still hungry may be the last to leave. The issue is discussed more widely in Why behavioural responses may not reflect the population consequences of human disturbance.

It’s not just waders : Little Egret being chased  along the shores of the River Bann SPA and (below) the last few Brent Geese being removed from saltmarsh on the Exe Estuary (SPA)

Potentially, roosting waders could be more prone to disturbance than feeding birds, because of the wasted energy associated with flying around over the high-tide period or relocating to an alternative roost site (see A place to roost). An interesting modelling paper by Mark Rehfisch and colleagues showed that 90% of Dunlin, Grey Plover and Redshank on the Wash could be serviced by roost sites that were 2 km, 2.5 km and 3.5 km apart, respectively (Applied Ecology). These numbers may or may not be comparable for Turnstone but do suggest that small- to medium-sized waders feed within relatively short distances of their preferred roosting areas.

Turnstone in this study

Turnstone is a species of qualifying interest for the Northumbria Coast Special Protection Area (SPA) and for several Sites of Special Scientific Interest (SSSI) in the region. On this 140 km stretch of coast, the population of Turnstone declined by 27% between 2004/5 and 2009/10, during a period when the wintering number within England declined by 9%. There was concern that human disturbance may be one of the drivers of the population decline of wintering Turmstone within the SPA. Potentially such conditions could become more challenging towards the end of the winter, when food supplies may be less and birds are preparing for migration, or during periods of very cold weather. Given an increase in the local human (and canine) population and a marked rise in tourism within the region, it was suggested that the potential for disturbance may have increased.

 

The aim of the study was to compare wintering Turnstone densities and changes in counts across time from sites with differing levels of human disturbance. This was possible because long-term Wetland Bird Survey counts of waders had been made in the period between 1998/99 and 2015/16. Counts were available for two offshore refuges and 17 mainland sites that were subject to higher levels of human disturbance. No direct measure of human disturbance was available so questionnaires were used to determine the behaviour of beach users, in terms of distance travelled to visit the coast. The paper contains full detail of this methodology.

Results

After controlling for the extent of preferred habitat (rocky shore) at each site the authors found that:

1. The closer each of the 19 sites was to the nearest offshore refuge the higher the density of Turnstones, where density is calculated as birds per hectare of suitable feeding habitat.
2. Turnstone counts at the four sites closest to, or containing, offshore refuges showed no significant declines. Despite the national decline in the number of wintering Turnstones, the counts on the Farne Islands and on St. Mary’s Island (both offshore islands) rose during the study period, although the rate of increase was not statistically significant from zero. There were declines at 15 of the 17 non-refuge sites. These results are consistent with the idea that, as populations decline generally, the sites of the highest quality (in this case those subject to less human disturbance) will show no, or slower, declines.
3. 65% of the walkers interviewed on beaches were exercising their dogs, 83% having travelled 6 km or less to get to the beach. No relationship was found between Turnstone counts and human population densities. There is more information in the paper about the amount of time that people spend on different types of beaches.

Graph showing Turnstone densities at different distances from refuges on the coast of northeast England. Figure from paper in Bird Study.

 

Implications

The authors of the Bird Study paper have not sought to explain declines in Turnstone numbers, but they have provided some useful references in the Discussion that highlight how improved water treatment and warmer winters might have affected regional distributions. They also remind us that Turnstone numbers are declining – as is the case for several High Arctic species. Having established that there are declines, they use the pattern of change to ask questions about whether disturbance is an issue for this species.

Seahouses, looking out towards The Farnes – not far, as the Turnstone flies

The results of the research suggest that Turnstones make greater use of relatively undisturbed areas (offshore refuges) than those subject to greater disturbance by humans and their four-legged friends. Previous work has shown that excessive disturbance prevents the use of roosts and that disturbance can have serious energetic consequences (see A place to roost). Although the paper does not distinguish between birds that are foraging or roosting, this study suggests greater provision of undisturbed sites (refuges) within, or close to, protected areas is important for Turnstones, especially if there is also a drive to build more houses and attract more tourists.

Beaches at Seaburn (County Durham) and Ross Back Sands (Northumberland). Proximity to human settlement makes a big difference! There are 15 dogs in the left-hand picture.

When looking at the planning process for developments close to SPAs, Mark Whittingham and his colleagues suggest that three issues need to be considered in some detail:

1. While it is valuable to consider the SPA as a whole, it is also important for decision-makers to consider the vulnerabilities of constituent parts of the site.  Thus, for planning decisions based upon environmental impact assessments, there is clearly a need to consider pressures on particularly vulnerable areas, e.g. those used for roosting.

2. 

   One of the tagged individuals that was tracked as part of a complementary study

   Studying the behaviour of marked individuals might help to pinpoint areas that are of critical importance. A separate, small-sample study of radio-tagged Turnstones in the area showed that these birds avoided mainland feeding and roosting areas at night, with at least some of the tagged Turnstones being found on offshore sites.

3. Species need to be considered separately when assessing disturbance issues because habitat use and resource distribution varies widely. The focus for Turnstones is on rocky coasts and this determines their choice of roosting sites. The requirements of red-listed Ringed Plover (for instance) may be very different, especially as they spend a lot of time feeding on the sort of open beaches that look great for exercising dogs.

Paper

Dogs are an important part of the disturbance issue.

The paper at the heart of this blog is:

Offshore refuges support higher densities and show slower population declines of wintering turnstones by Mark J. Whittingham, Ailsa J.  McKenzie, Richard M. Francksen, David Feige, Tom Cadwallender, Matthew Grainger, Nadheer Fazaa, Caroline Rhymer, Catherine Wilkinson, Pauline Lloyd, Ben Smurthwaite, Steve M. Percival, Tammy Morris-Hale, Clare Rawcliffe, Claire Dewson, Sarah Woods, Gavin B. Stewart & Elizabeth Oughton. Bird Study DOI  10.1080/00063657.2020.1713725

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

 

 

Wetland Bird Survey: working for waders

Red-listed Curlews, Scottish Oystercatchers, a boom in Black-tailed Godwits and the need for safe roost sites. Here’s a selection of WaderTales blogs that may appeal to counters who contribute to the UK Wetland Bird Survey (WeBS) and other birdwatchers who like waders/shorebirds.

It’s over 70 years since UK birdwatchers started to count waders and waterfowl and there are now over 3000 registered Wetland Bird Survey volunteers.

The work that volunteers do to chart the rises and falls of species as diverse as Redshanks and Whooper Swans provides a unique insight into the fortunes of our wintering waterbirds. As a tribute to the people behind the binoculars and telescopes, a few WaderTales articles that use WeBS data are highlighted below. Click on the links in bold if you want to read a particular story. Link to latest WeBS report.

Curlew counts

WeBS counts for Curlew in Great Britain between 1974 and 2016

In the blog Is the Curlew really near-threatened? WeBS counts are used to show how numbers have changed over the decades. There might have been a boost in numbers when Curlew came off the hunting quarry list in Great Britain in 1981 but declines in the last 15 years reflect issues birds face in the breeding season in many parts of their European range.

This blog discusses how much the 1980 to 1995 recovery in winter numbers can be attributed to hunting – After the hunting stopped.

Internationally, Eurasian Curlews are classified as near-threatened and in the UK they are now red listed. WeBS counts in Northern Ireland, alongside I-WeBS counts in the Republic, were successfully used to argue for the cessation of shooting across the island of Ireland in 2012.

Scottish and Welsh Oystercatchers

Oystercatchers are unusual, amongst waders, in that they feed their young

Surely the Oystercatcher is one wader species that we don’t need to worry about? Although the blog Oystercatcher: from shingle beach to roof-top leads with nesting behaviour, WeBS counts are used to illustrate regional trends in different parts of the United Kingdom. In Scotland, there is concern about poor breeding success, while in parts of Wales and England, WeBS counts may provide a way of measuring the population-level effects of cockle fishing and diseases affecting shellfish.

Three very different trajectories for national WeBS counts for Oystercatchers since 1974

WeBS counts were used to explain what happened to the Oystercatchers that winter in South Wales when cockle numbers collapsed. One of the key messages from the study is that it is really important to protect networks of sites, to give waders alternative feeding sites when conditions change. See When Oystercatchers can’t find food.

Mid-winter movements

The annual WeBS report highlights the months in which counts are at their highest in different estuaries. For Knot, for instance, the highest counts on the Wash are in September, in other east-coast estuaries and on the Dee the peak is in December, whilst further north, in Morecambe Bay and the Solway, top numbers occur in January and February.

In Godwits & Godwiteers, which focuses on the superb work of observers who track the movements of colour-ringed Black-tailed Godwits, WeBS counts from east coast estuaries and the Ouse Washes illustrate the move inland that occurs as the winter progresses.

Population estimates

These two blogs review the latest wader population estimates for Great Britain and the island of Ireland

National patterns and local counts

Groups of WeBS counters who cover local estuaries will be the first to notice changes in the numbers of the key species that use their own sites. If the number of Dunlin drops, is that a local phenomenon or part of a national picture? Is there always a strong link between national declines (or increases) and site-based counts? Interpreting changing wader counts provides some answers. It emphasises just how reluctant waders are to change wintering sites between years.

High-tide roosts

Every WeBS counter will appreciate the value of a safe (undisturbed) roosting site, whether this be used by waders or by ducks and geese. In A place to roost, WeBS counts for Black-tailed Godwits are used to assess the national and international importance of an individual roosting site in northwest England. The main thread, however, is about the energy expenditure associated with sleeping (not very much) and travelling to and from a safe roost site (lots). An interesting add-on is the story of what happened to Cardiff’s Redshanks when the estuary was turned into a lake.

New recruits

If adult birds don’t change their winter homes then increases in local populations may well reflect good breeding years for wader species. 2017 was a good year for several species that breed in Iceland, particularly Black-tailed Godwits. A great summer for Iceland’s waders puts the year’s productivity into context and gives an update on wader research that is being undertaken by the South Iceland Research Centre (University of Iceland), the University of East Anglia (UK) and the University of Aveiro (Portugal). If you have ever seen a colour-ringed Black-tailed Godwit, Ringed Plover, Oystercatcher or Whimbrel you may well find this interesting.

On the open shore

The blog News & Oystercatchers was written to promote the Non-estuarine Waterbird Survey of 2015/16, or NEWS-III. There are a lot of waders on the shorelines that link the estuaries that are covered for WeBS and, every few years, volunteers are asked to count these birds. In NEWS-II (2006/07), it was estimated that 87% of Purple Sandpipers were to be found on the open shore (see table) with high numbers of several other species.

There’s an assessment of the results from NEWS-III in Waders on the Coast.

The UK Red List

The UK holds hugely important numbers of wintering waders. This is emphasised in the blog UK Waders: “Into the Red”. There will be no surprise that Curlew is on the list but would Ringed Plover be on your ‘red list’? Dunlin and Purple Sandpiper are both recent additions, on the back of the NEWS-III counts.

New and increased threats (an addition in Nov 2022)

Diseases, changes in habitat quality and pressure from developers are not new threats to the UK’s waders but, after a period of relative calm, there are several reasons to be worried.

• HPAI has decimated seabird populations and we know that waders are at risk too. WeBS counts will monitor the seriousness of outbreaks.
• Lack of investment in sewage treatment, coupled with more frequent heavy downpours, is impacting on our estuaries and beaches. Mats of algae can reduce feeding opportunities and who knows what our waders will end up eating? Low-tide counts, in particular, will be valuable when trying to detect displacements of flocks.
• Wind energy is relatively cheap and clean but turbines need to be sited sensibly. WeBS counts, Low-tide counts and tracking will help planners, government agencies and NGO’s to minimise impacts on migrating waders.
• Given the increased price of electricity, the economic viability of tidal barrage schemes has increased. Up-to-date information is going to be important, as NGOs try to minimise habitat destruction.
• Estuaries have been pretty well protected under European legislation and it is not surprising that more unscrupulous developers are seeking opportunities to grab ‘unused’ land, emboldened by freeports and under-funded country agencies. Here’s hoping that conservation values will be maintained.
• There is an increasing realisation that waders, such as Curlew, Oystercatcher and Black-tailed Godwit need feeding areas above the high-tide mark. We need to make sure that WeBS counts are covering these sites. Birdwatchers can help by counting waders on playing fields, farmland and potential development sites, and reporting them via BirdTrack.

Many more blogs to choose from

There are over 130 WaderTales blogs to choose from in this list. Five of these articles might be of particular interest to WeBS counters:

• 

  Knot migration

  Which wader, when and why? gives an overview of the migration of waders into, out of and through Britain & Ireland. The patterns help to explain why the peak numbers for Sanderling occur on the Wash in August, on the Dee in November and on the North Norfolk coast in May, for instance.

• Bar-tailed Godwits: migration & survival  contrasts the different migration patterns of the two races of Bar-tailed Godwits that use British & Irish estuaries and explains the importance of colour-rings in the calculation of survival rates. On the other side of the world, Wader declines in the shrinking Yellow Sea shows how quickly numbers can change if the annual survival probabilities of adults fall. 
• The not-so-Grey Plover focuses on the Grey or Black-bellied Plover but the real story is about moult. British and Irish estuaries are important to huge numbers of moulting waders. WeBS counters often don’t have time to look at individual birds but, with the right camera, you can learn a lot about waders by checking out the right feathers. The Grey Plover is an under-studied species but we are starting to learn more about these Plovers from the north.

Thank you

I use WeBS data a lot – in my blogs and in articles – and I appreciate the tremendous value of data collected each month by thousands of contributors. They monitor the condition of their local patches and have directly contributed to local, national and international reviews of the conservation status of wintering waterbirds. To every current and past WeBS counter – ‘thank you!’

There’s a (large) selection of papers using WeBS data here, on the BTO website. The Wetland Bird Survey is run by the BTO, in partnership with RSPB and JNCC (which acts on behalf of NE, NRW, SNH & DAERA), and in association with WWT.

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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

Flyway from Ireland to Iceland

The Ireland to Iceland air link opens in February and does not close until well into May, as swans, geese, ducks, waders, gulls and passerines head north. At the end of June it opens again, with the first failed breeders returning to Ireland. Species such as Oystercatcher and Black-tailed Godwit spend much more of the year in Ireland than they do in Iceland.

Most Oystercatchers are being ringed with two letter engraved rings, along with two colour-rings: Photo Tómas Gunnarsson

The island of Ireland holds important populations of waders in the wintertime – everything from Grey Plovers from Siberia to Turnstones from Canada – but there is  special relationship with Iceland. It’s the next stopping off point for passage Sanderling, as they fly from Africa to Greenland, and the ultimate destination for lots of wintering birds such as Snipe, Redshank and Golden Plovers.

Oystercatchers lead the way

A lot of the Oystercatchers seen around Ireland’s coastline breed in Iceland, as has been shown by the Dublin Bay Birds Project. Birds start moving north very early, as shown by the appearance of yellow-ringed Dublin Bay birds in Tiree before the end of February each year. Migratory decisions for Icelandic Oystercatchers explains how a new Icelandic project is examining the costs and benefits of being a migrant. Irish reports of Icelandic colour-ringed birds are helping to provide answers – and the Dublin Bay birds are providing great additional data. The first paper to come out of this project is summarised in Which Icelandic Oystercatchers cross the Atlantic?

Each autumn, Irish-breeding Snipe are joined by much larger numbers from the north and east. About a quarter of foreign-ringed snipe that have been found in the island of Ireland are of Icelandic origin, compared to just one out of 255 in England. Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

Some of the later waders to use the Ireland to Iceland flyway are Whimbrels, many of which stop off in Ireland on spring migration. Whimbrels on the move summarises a paper about the movements of Icelandic, ringed Whimbrel. Since its publication, a new paper has shown that Whimbrel are able to fly between Iceland and west Africa in one jump but that they sometimes need to stop off on the way north. See Very rapid long-distance sea crossing by a migratory bird by José Alves and colleagues and Iceland to Africa non-stop by Camilo Carneiro and colleagues. Camilo has shown that individual birds leave Africa at the same time each year so it is not surprising that spring passage in Ireland is so consistent in its timing (Whimbrel: time to leave).

Black tailed-Godwits

WaderTales was invented as a way of providing feedback to colour-ring readers who focused on Black-tailed Godwits. There are 19 blogs about the species, some of which may well appeal to birdwatchers who have spotted colour-ringed birds anywhere between Belfast Harbour and the Shannon Estuary.

We are all aware that migration is getting earlier but how does this happen? Monitoring the annual arrival of individual colour-ringed Black-tailed Godwits in Iceland may well have provided an answer. Why is spring migration getting earlier? reveals that it is new recruits into the breeding population that are setting the pace; they are reaching Iceland earlier than previous generations.

Another fascinating story that is revealed by colour-ringing is the synchronous arrival in Iceland of the two members of breeding pairs of Black-tailed Godwits, even if one wintered in Ireland and the other in France. You can read more here.

Wintering waders

Ireland is a very important winter destination for Iceland’s Redshank, Golden Plover and Snipe. You can read more in Ireland’s wintering waders, a blog based on the most recent population estimates for the island of Ireland, generated from WeBS data in Northern Ireland and I-WeBS in the Republic. A paper in Irish Birds revealed a 20% drop in wader numbers over a five-year period. One of the biggest declines was in Redshank, most of which will be of Icelandic origin. We don’t really know what is happening to winter numbers of Golden Plover or Snipe.

Greenland and Canada

Each spring, thousands of waders pass through Ireland on their way from Africa to Iceland, and beyond to Greenland and Canada. By the end of the first week of May, most of the waders that breed in Iceland (Black-tailed Godwit, Whimbrel, Redshank, Oystercatcher, Snipe and Golden Plover) will be on territory but birds headed further north are on a later schedule.

The month of May sees departures of Sanderling, Turnstone and Knot that have spent the winter around the coasts of Ireland. Before they go, their numbers will be swelled with the addition of newly-arrived flocks from Africa and southern Europe. The blog Travel advice for Sanderling, reveals fascinating research results about Sanderling migration, generated by thousands of reports of colour-ringed birds. Why do some Sanderling travel all the way from Greenland to South Africa when they could do just as well by staying in Ireland?

Most of these May-departure flocks of waders, which also include Dunlin and Ringed Plover, will stop off in Iceland to refuel and to await good conditions for the next stage of their journeys to the Arctic.

Breeding Waders

WaderTales were developed in East Anglia so many of the articles about breeding waders have an English feel to them. Hopefully, some of the blogs will still appeal. Anyone trying to support breeding Lapwing populations might be interested in A helping hand for Lapwings, which also talks about Redshank. In a more recent blog, Tool-kit for wader conservation, there’s a summary of techniques available to conservationists who focus on waders breeding on lowland wet grassland.

There’s an Icelandic focus to WaderTales too and a blog, which looks at the attitudes of farmers. This may well resonate with conservationists (scientists, birdwatchers and farmers) who are trying to work together to improve conditions for Irish breeding waders. As Icelandic farming expands, what are farmers prepared to do to support breeding waders, many of which are destined to spend the winter on Irish estuaries. See: Do Iceland’s farmers care about wader conservation?

Ireland – a special place for Curlews

Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Is the Curlew really near-threatened? considers the plight of breeding Curlew. It’s easy to understand why BirdWatch Ireland, RSPB, BTO, WWT and GWCT  are focusing on this species How long will it be until breeding Curlew are lost from Ireland, completely?

The threat to the Curlew is real, especially when set in an international context. Two species of curlew are probably already extinct and other members of the Numeniini (curlews, godwits and Upland Sandpiper) are facing a similar set of problems to those that probably caused the demise of the Eskimo Curlew and Slender-billed Curlew. Why are we losing our large waders? outlines the background to a global problem.

There’s a WaderTales blog that summarises a paper from BTO and RSPB – Curlews can’t wait for a treatment plan. Although the analyses are based on British data, the results are highly relevant to Irish Curlews.  If you prefer your Curlew writing to be more lyrical, please read Curlew Moon which has it its heart the similarly titled book by Mary Colwell.

A more recent Curlew blog reveals the results of the Irish breeding survey in the summers of 2015, 2016 & 2017, with the shocking headline figure of a 96% decline: Ireland’s Curlew Crisis.

Conservation issues

Hundreds of  birdwatchers take part in the Irish Wetland Bird Survey (Republic) and the Wetland Bird Survey (Northern Ireland). These counts identify and monitor key sites for wintering waders – and wildfowl. Whilst mud  and sand-flats are, of course, important to waders, so are roost sites. A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. It has been estimated that the cost of flying to and from roosts might account for up to 14% of a bird’s daily energy expenditure. That’s something to think about next time you see a dog chasing off a flock of roosting waders. This blog about Disturbed Turnstone suggests that pressures from people (and dogs) can cause a redistribution of wintering birds.

Further reading

Hopefully, this summary  gives a flavour of some of the issues being faced by Irish waders and the research to which they are contributing. There are already over 90 blogs in the WaderTales series, with one or two new blogs being produced each month. If you want to know how volcanoes affect breeding waders in Iceland, why Black-tailed Godwits wear colour-rings or if there are costs to carrying a geolocator have a look here.

And finally …

There’s a useful summary about wader migration to, from and through Ireland in Which wader, when and why?

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

Wales: a special place for waders

From winter beaches to summer moorland and woodland, Wales provides essential habitats for waders. This blog was originally written in 2017, to bring together WaderTales stories that were of particular relevance to Welsh birdwatchers. The publication of Birds of Conservation Concern Wales 4, in 2022, created the perfect excuse for a revamp. The first part of the blog focuses on BoCCW4. This is followed by updated sections about the birds that spend winter in Wales, pass through in spring and autumn, and breed in the country.

Birds of Conservation Concern Wales 4, published in 2022, includes ten red-listed and fourteen amber-listed waders.

There are five changes to the Red, Amber and Green lists since BoCCW3 was published in 2016. Purple Sandpiper has joined the Red list but there have been four improvements:

• Avocet has moved from Amber to Green, reflecting the fact that the species can no longer be considered as a rare breeder.
• Sanderling in now green-listed, due to a reassessment of the size of the species’ international population.
• Knot has moved from Red to Amber, as the long-term decline in the number of birds wintering in Wales is measured as 22% (rather than 56%)
• Common Sandpiper has moved to the Amber list too, with the decline in breeding numbers now estimated as 28% (rather than 51%)

Unsurprisingly, there is significant overlap between BoCCW4 and the UK red and amber lists but there are some important differences too. There is a WaderTales blog about the UK list: Into the Red.

Red-listed in Wales & UK

Curlew (right) – The decline in breeding numbers is particularly worrying in Wales and the species is now the focus of a special conservation partnership: Gylfinir Cymru / Curlew Wales. More below.

Dunlin – Very few pairs of the schinzii race still breed in Wales and there are declining numbers of wintering alpina birds on estuaries. This WaderTales blog discusses issues for schinzii in Baltic countries.

Lapwing – Breeding numbers have dropped significantly. Here’s a blog with suggestions as to how to help Lapwings and other waders breeding in lowland wet grassland: Toolkit for wader conservation.

Purple Sandpiper – Added to the UK red list in 2021 and to the Welsh list in 2022, reflecting falling numbers of wintering birds.

Ringed Plover – A significant part of the hiaticula race of Ringed Plover winters in Wales, with ringing recoveries linking the country with Baltic and mainland-Europe populations. Nesting pairs are threatened by recreational pressures, developments and rising sea-levels, as discussed in this blog about the situation in eastern England.

Woodcock – Declining as a breeding species but still present in large numbers in wintertime. More below.

Red-listed in Wales but not UK

Bar-tailed Godwit (right) – Winter visitors on Welsh estuaries are of the lapponica race, birds that breed from Scandinavia through to western Russia. Red listing in Wales reflects the relative importance of these western areas of Britain for Bar-tailed Godwits and recent declines in numbers. It is possible that young birds are now wintering further east than previous generations, on the European coast. This may reflect warmer winter conditions.

Golden Plover – Large numbers winter in Wales, with birds arriving from Iceland, northern Britain and Europe. Flocks can become particularly impressive if persistent cold weather pushes European birds further west.

Grey Plover – We don’t know enough about these Siberian visitors, as discussed in Plovers from the North but Welsh estuaries seem to be important. Numbers were much larger at the and of the twentieth century and there is a continuing decline.

Redshank – Breeding numbers have declined significantly across the whole of the UK and it will not be long until they are red-listed elsewhere. More below.

Red-listed in UK but not Wales

Dotterel – Breed in the high tops of Scotland and occasionally elsewhere in the UK. Red-listing reflects low numbers and a continuing decline, as discussed in Scotland’s Dotterel: still hanging on. Welsh birdwatchers look forward to seeing passage birds on sites such as the Great Orme. Amber-listed in Wales.

Whimbrel – Red-listed in the UK because of declining Scottish population. Wales provides spring feeding for large numbers of migrant Whimbrel in spring, which explains the species’ amber-listing. More below.

Red-necked Phalarope – Red-listed in the UK because there is a very small (but stable) breeding population on Scottish islands.

Black-tailed Godwit – Red listed in UK because the small English breeding population needs all the help it can get. See England’s Black-tailed Godwits. Amber-listed in Wales because the country is a winter home to large numbers of the islandica subspecies.

Ruff – Red listed in the UK because occasional pairs breed. Amber-listed in Wales because of the small but important wintering population.

There are over one hundred WaderTales blogs so far. Here’s a selection that may well appeal to birdwatchers in Wales.

Welsh winter beaches & estuaries

Most Oystercatchers are being ringed with two letter engraved rings, along with two colour-rings: Photo Tómas Gunnarsson

Wales holds important populations of waders in the wintertime – everything from Grey Plovers from Siberia to Turnstones from Canada. There is a particularly strong link to Iceland.

Some of the Oystercatchers seen in sites such as the Burry Inlet or the Menai Strait are from Iceland, where they can be found alongside Redshanks and Golden Plover that have also arrived from the north.

Migratory decisions for Icelandic Oystercatchers describes a project to examine the costs and benefits of being a migrant. Welsh reports of Icelandic colour-ringed birds are helping to provide answers.

• The first paper by Verónica Méndez and colleagues is described in Which Oystercatchers cross the Atlantic?
• In the second, we learn that the migratory behaviour of chicks is linked to the behaviour of fathers, not mothers: The Dad Effect.
• Which Oystercatcher pairs are most successful and what happens if a migrant pairs with a resident? The answers are discussed in When mates behave differently.

Not all of the Oystercatchers on Welsh estuaries come from Iceland, there are lots from Scandinavia too. When Burry Inlet shellfishers persuaded the UK government to start a programme of Oystercatcher culling in the 1970s there was a strong reaction from Norway. It has since been shown that cockle supply is more influenced by pollution and disease than by predation by birds, as discussed in When Oystercatchers can’t find food.

Turning from the open mudflat, birdwatchers may well see Snipe probing in wet patches in the saltmarsh. Interestingly, the migratory provenance of Welsh Snipe seems to be very different to that of Irish ones. A quarter of foreign-ringed Snipe reported in Ireland have been found to be wearing Icelandic rings but, so far, no Reykjavik-ringed Snipe have been spotted in Wales. Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

You may be lucky enough to have Greenshanks wintering on a local Welsh estuary. These birds are likely to be from the Scottish breeding population, as you can read here: Migration of Scottish Greenshank.

Protecting key wintering sites is a high priority when it comes to wader conservation. A BTO and WWT project aimed to provide better information as to how species as diverse as Dunlin and Shelduck make use of the Severn Estuary. This was important work, with major relevance to discussions as to how power might be generated within the estuary. Tracking waders on the Severn urged birdwatchers to look for colour-marked birds. Initial results, shared at an International Wader Study Group conference, indicate that the home range of a Redshank is ten times as big as originally thought, with birds being particularly mobile at night.

Hundreds of Welsh birdwatchers take part in the Wetland Bird Survey and the intensive work involved in periodic Low Tide Counts. These identify and monitor key sites and establish the most important feeding areas within estuaries. Whilst mud and sand-flats are, of course, important to waders, so are roost sites. A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. It has been estimated that the cost of flying to and from roosts might account for up to 14% of a bird’s daily energy expenditure. That’s something to think about next time you see a dog chasing off a flock of roosting waders. A second WaderTales blog focuses upon how disturbance affects wintering Turnstone.

These blogs reveals the latest trends in numbers of Britain’s wintering waders: Do population estimates matter? and Waders on the Coast. Most species are less numerous but the Black-tailed Godwit bucks the trend. Warmer British winters may be providing easier conditions for these smart waders but this paper shows how spring conditions in Iceland are providing expanding breeding opportunities: From local warming to range expansion.

Passing through

There is exciting work going on in Wales, to understand why so many Whimbrel spend time in the country in the spring. Whimbrels on the move summarises a paper about the movements of Icelandic, ringed Whimbrel. Since its publication, a paper has shown that Whimbrel are able to fly between Iceland and west Africa in one jump but that they usually need to stop off on the way north. See Iceland to Africa non-stop. This is part of a bigger Icelandic study which is summarised in A Whimbrel’s Year.

Some waders are more mobile than others. Although both Grey Plover and Knot are ‘winter visitors’, ringing has shown that they move around the estuaries bordering the Irish Sea, during the period from October to April. Colour-ringing studies aim to help us to understand the importance of this network of sites to Knot from Canada and Greenland and Grey Plover from Siberia. Welsh birdwatchers can help by reporting birds wearing lettered flags on their legs.

Each spring, Welsh beaches see influxes of Sanderling, Ringed Plover, Turnstone and Dunlin, as birds pass through on their way from Africa to Iceland, Greenland and Canada. Some of the smart summer-plumage Sanderling could have travelled from South Africa, Senegal or Portugal but others spend the winter in Wales. This fascinating paper gives Travel advice to Sanderling.

There’s a blog on the subject of wader migration if you want a quick summary for 40 or more species: Which wader, when and why?

Breeding Waders

Wales provides homes to many breeding waders, from Ringed Plover on the coast, via Little Ringed Plover and Common Sandpiper along rivers and into the moorland for Curlew and Dunlin, passing a forest with Woodcock en route. And that’s only giving a mention to half of the country’s breeding wader species.

Starting on salt-marsh, Big-foot and the Redshank nest investigates appropriate cattle stocking levels for successful Redshank breeding. Although the work was undertaken in northwest England, there is no reason to believe that Welsh cattle are any less careful as to where they put their feet. This paper shows that salt-marsh Redshank are in trouble: Redshank -the warden of the marshes.

We are all aware of the issues facing farmland waders. The next blog is about research in Scotland but the story it tells, of declining numbers of species such as Redshank and Lapwing, could have been written about Wales. Here, you can read how farming has changed and the impacts that this has had upon breeding waders: 25 years of wader declines.

Spring sees the return of Common Sandpipers from Africa, to nest along Welsh rivers and around reservoirs. Not-so-Common Sandpipers  describes the migration and decline of this much-loved species.

Is the Curlew really near-threatened? considers the plight of breeding Curlew. It’s easy to understand why RSPB, BTO, WWT, GWCT and BirdWatch Ireland are focusing on this species. You can read about Ireland’s Curlew Crisis here. The Welsh decline is not as serious as the one in Ireland, where the number of breeding pairs has dropped from 3300 to 138 pairs, but you still have to ask: How long will it be until breeding Curlew are lost from Wales?

This blog summarises the threats to breeding Curlew across Great Britain: Curlews can’t wait for a treatment plan.

Research by RSPB in Wales has focused on specific issues relating to grazing: Sheep numbers and Welsh Curlews.

One of the potential problems for Curlews and other waders is a planned increase in tree cover. As Wales strives for carbon capture and sustainability, it will be sad if habitat loss and increased cover for predators cause more problems for threatened species. These two stories from Iceland and Estonia highlight these issues: Iceland’s waders need a strategic forestry plan and Keep away from the trees.

Predation is acknowledged as a major issue for nesting Curlew but is this a problem for Oystercatchers too? Oystercatchers: from shingle beach to roof-tops reveals a significant decline of the species in Scotland, mediated to some extent by range expansion in three dimensions.

The strangest Welsh wader has to be the Woodcock – probing about in winter fields and nesting in forestry plantations. Conserving British-breeding Woodcock focuses on worrying results from the last GWCT/BTO survey and work to reduce losses during the shooting season.

Further reading

Hopefully, this summary  gives a flavour of some of the issues being faced by Welsh waders and the research to which they are contributing. There are already over 100 blogs in the WaderTales series, with one or two new blogs being produced each month. If you want to know more about wader migration or moult, how volcanoes affect breeding waders in Iceland, why Black-tailed Godwits wear colour-rings or if there are costs to carrying a geolocator have a look here.

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

WaderTales: a taste of Scotland

Why is Scotland losing its breeding waders? The latest WaderTales blog with a Scottish flavour is a story from Strathallan, based on observations by Mike Bell.

“If you’ve taken the A9 north of Stirling, through Strathallan, perhaps you might have noticed displaying Lapwing, Oystercatcher, Curlew and Redshank? Over a 25-year period, the number of breeding waders in this valley and another one that runs northwest and that can be seen from the B827 has dropped from 600 pairs to just 76 – that’s a loss of 87%, or over 20 pairs per year.”

Click here for a link to the blog

 

And here are five more uniquely Scottish WaderTales blogs

Waiting for the wind – spring flocks of Black-tailed Godwit on Scotland Observations from Tiree by John Bowler and others gave a unique insight into what happens if northerly winds set in at migration time.

Establishing breeding requirements of Whimbrel  focuses on the different habitat needs of adults and chicks in Shetland.

Oystercatchers: from shingle beach to roof-tops details significant declines in Scotland, at least partly explained by predation. An increasing number have now taken to nesting on roofs.

UK Dotterel numbers have fallen by 57% presents the results of an RSPB survey that was published in Bird Study.

Prickly problems for waders explains how SNH are trying to deal with introduced Hedgehogs in the Outer Hebrides, where they are a major problem for breeding waders.

And here are another nine which may well appeal to Scottish birdwatchers:

• Conserving British-breeding Woodcock focuses on worrying results from the latest GWCT/BTO survey and work to reduce losses during the shooting season.

• Why do Turnstones eat chips? asks why we sometimes see waders feeding on unusual foods. Is this opportunism or desperation?

• Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

• NEWS and Oystercatchers focuses on the waders that  winter on coasts, instead of estuaries. It was written to promote the 205/16 coastal survey run by BTO.

• Is the Curlew really near-threatened? considers the plight of breeding Curlew. It’s easy to understand why RSPB and BTO are focusing on this species.

• A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. What are waders looking for?

• Which wader, when and why? summarises the annual migration patterns of over 40 species of wader that visit Britain and Ireland.

• The not-so-Grey Plover focuses on the moult of the Grey Plover but the principles are relevant to determining the ages of birds of other species.

• Interpreting changing wader counts looks at the links between local and national wader counts, with consequences for site-based species protection.

There are over 40 WaderTales blogs. The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published.

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

A place to roost

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

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

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

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

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

• 

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

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

The details can be found here:

• Roost availability may constrain shorebird distribution: Exploring the energetic costs of roosting and disturbance around a tropical bay. Danny I. Rogers, Theunis Piersma & Chris J. Hassell. Biological Conservation 133 (2006) 225-235
• High-tide habitat choice: insights from modelling roost selection by shorebirds around a tropical bay. Danny I. Rogers, Phil F Battley, Theunis Piersma, Jan A van Gils & Ken G. Rogers. Animal Behaviour, 2006, 72, 563-575

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

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

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

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

Consequences of roost loss

Colour-marked Redshank demonstrated the individual consequences of habitat loss

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

• Burton, N.H.K. 2000. Winter site-fidelity and survival of Redshank at Cardiff, South Wales. Bird Study 47: 102–112.
• Burton, N.H.K. & Armitage, M.J.S. 2005. Differences in the diurnal and nocturnal use of intertidal feeding grounds by Redshank. Bird Study 52: 120-128.
• Burton, N.H.K., Rehfisch, M.M., Clark, N.A. & Dodd, S.G. 2006. Impacts of sudden winter habitat loss on the body condition and survival of Redshank. Journal of Applied Ecology 43: 464-473

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

Importance of individual sites

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

Conservation

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

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

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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