Do population estimates matter?

blog top godwitsThis month (March 2019) saw the publication of Population estimates of wintering waterbirds in Great Britain, which includes all the wader species from Little Stint to Curlew. Given that the Wetland Bird Survey already covers about 2000 wetlands and provides annual monitoring, why do we need to know the total number of birds in Great Britain?

I suggest four reasons:

  • If we count the number of Curlew and we have a figure for the European population then we know that Great Britain is responsible for nearly 20% of Europe’s Curlew each winter, thereby strengthening the case for national conservation action;
  • If we have a national figure, then we know that a flock of 2000 Black-tailed Godwit represents (as it turns out) over 5% of the British total, which is a useful criterion when assessing the conservation importance of individual sites;
  • blog GKPopulation totals help to put annual percentage changes into context;
  • And simply because people ask questions such as “how many Greenshank are there in the country during the winter?”

So, here’s the bottom line. In their 2019 review of waterbird numbers in British Birds, a team from BTO, WWT, JNCC & RSPB reveal that an estimated total of 4.9 million waders spend the winter in Great Britain. That’s about one third of all waders on the East Atlantic Flyway. Impressive!

Please note that Northern Ireland figures are included in an upcoming report for the island of Ireland.

Making the counts

The population estimates owe a lot to those who undertake monthly Wetland Bird Survey (WeBS) counts on estuaries, lakes and waterways, during the winter months, year in and year out. Counts from the period 2012/13 to 2016/17 are used in the population estimates that form the basis for the 2019 review. WeBS data have many other uses, as you can read here: Wetland Bird Survey: working for waders.

blog CUFor species of wader that also make use of the open coast, the Non-estuarine Waterbirds Survey of 2015/16 (or NEWS III) provided additional data, updating the NEWS II figures from 2006/07. The vast majority of our wintering Purple Sandpipers are found on open beaches and rocky shores, as well as large numbers of Turnstone, Ringed Plover and Sanderling, together with significant numbers of Oystercatcher, Curlew and Redshank. There’s more about NEWS in this slightly dated blog: NEWS and Oystercatchers for Christmas.

The last assessment of winter wader populations was made by the Avian Population Estimates Panel and published in British Birds in 2013 as Population estimates of birds in Great Britain and the United Kingdom (APEP3). In here, estimates for waders were largely based on WeBS data for the period 2004-09 and NEWS II. The new assessment is presented as Population estimates of wintering waterbirds in Great Britain and also published in British Birds. It uses WeBS information for the period 2012-17 and NEWS III data. Effectively, there is an 8-year or 9-year difference between the two sets of figures.

The biggest losers

blog graphicGreat Britain is extremely important in the context of the East Atlantic Flyway, as is obvious from the fact that the area holds nearly five million waders. The WeBs counts already monitor the ups and downs on an annual basis but this review provides an opportunity to turn the percentages into actual numbers. It is concerning that, over a period representing less than a decade, the average maximum winter count for six of the species that were surveyed dropped by a total of over 150,000. These big losers were Knot, Oystercatcher, Redshank, Curlew, Grey Plover and Dunlin, ordered by number of birds lost, with Knot seeing the biggest absolute decline.

In preparing the new estimates for the British Birds paper, an opportunity was taken to refine the way that populations are calculated, based on Use of environmental stratification to derive non-breeding population estimates of dispersed waterbirds in Great Britain, by Verónica Méndez et al. The new methodology explains some of the differences between percentage changes reported by WeBS and the percentage changes obtained by comparing the latest population estimates to those in APEP3.

blog KN graphic

The Knot estimate dropped from 320,000 to 260,000. This figure is higher than might be expected from the counts that take place at sites covered by WeBS, being larger than the ten-year decline of 14% reported in the last WeBS report. Knot are mobile species within the North Sea and Atlantic Coast wintering area and it is possible that British losses may be explained, at least to some extent, by redistribution.

blog oyc graphThe drop in Oystercatcher numbers from 320,000 to 290,000 appears to be less than 10%, compared to a ten-year decline of 12% on WeBS. Improved analysis of NEWS data helped to add some more birds to the open-coast estimate so the 10% fall may underestimate the seriousness of the Oystercatcher situation. The 25-year Oystercatcher decline on WeBS is 26%, which is not surprising if you look at the changes to breeding numbers in Scotland, where most British birds are to be found. There’s more about this in: From shingle beach to roof-top.

blog RKThe Redshank decline of 26,000 is higher than would be predicted from WeBS figures, suggesting a drop of over 20% since APEP3, rather than ‘just’ 15% for the ten-year WeBS figure. This is a species that also features strongly in the Non-estuarine Waterbird Survey and that might explain the difference. Wintering Redshank are mostly of British and Icelandic origin, with the Breeding Bird Survey (BBS) suggesting a ten-year decline of 24% in our British breeding birds.

The Curlew is now globally recognised as near-threatened. The latest winter estimate is 120,000, down from 140,000 in APEP3. The new total represents between 14% and 19% of the European population, which means that we have a particular responsibility for this much-loved species. Only the Netherlands holds more wintering Curlew than Great Britain. Is the Curlew really nearly-threatened? is one of several blogs about Curlew in the WaderTales catalogue at www.wadertales.wordpress/about .

blog 2 DNIt has been suggested that the long-term declines of Grey Plover and Dunlin  may be associated with short-stopping, with new generations of both species wintering closer to their eastern breeding grounds than used to be the case. WeBS results indicate a 31% drop in Grey Plover and a 42% drop in Dunlin, over the last 25 years. There was a loss of 10,000 for both species between APEP3 and the new review, representing declines of 23% and 3% respectively.

The biggest winners

There are four big winners in the period between APEP3 (2004-09) and the new review (2012-16), although, even here, not all as it seems.

The Avocet has seen further dramatic gains. with the estimated wintering population rising to 8,700. The increase is not quite as big as might have been expected, based on the 43% rise seen in ten years of WeBS counts, but it is still a dramatic continuation of a 40-year trend.

The numbers of Bar-tailed Godwit and Ringed Plover are both substantially higher but at least a proportion of each of these changes is linked to the better coverage and more sophisticated sampling methods that were discussed earlier. Bar-tailed Godwit increases may also reflect redistribution around the North Sea.

blog BW graphOne of the consequences of improved statistical techniques, as used this time around, is the apparent decline in the estimated population of Black-tailed Godwit. The new figure of 39,000 is 4,000 smaller than in APEP3, despite the fact that the WeBS graph clearly shows an increase. Interpolation using WeBs figures suggests that the earlier population estimate should have been 31,000, rather than 43,000.

There are other winners too, as you can read in the paper. At the start, I posed the question “how many Greenshank are there in the country during the winter?”.  The answer is 810, representing an increase of 200 since APEP3.

Game species

The estimates for the three wintering waders that are still on the UK quarry list have not changed since APEP3 (published in 2011) as there are no new data available.

Golden Plover: The winter estimate remains as 400,000, as there has been no comprehensive, winter survey since 2006/7. Large numbers of Golden Plover arrive from Scandinavia, Europe and Iceland in the late summer, joining the British birds that choose not to migrate south or west. The GB breeding population is probably less than 50,000 pairs. Most breed in Scotland which has seen a breeding decline of 23% in the period 1995 to 2016 (BBS). Golden Plover is still ‘green listed’.

snipe-headerSnipe (Common): The winter estimate remains as 1,100,000 – a figure that was acknowledged in APEP3 as being less reliable than that of most species. At the same time, the GB breeding population was estimated as 76,000 pairs, indicating at least a 4:1 ratio of foreign to British birds, and that does not take account of the number of British birds that migrate south and west. Snipe are ‘amber listed’ but BBS suggests a recent increase of 26% (1995-2016). There is a WaderTales blog about  Snipe and Jack Snipe.

Woodcock: The winter estimate remains as 1,400,000 – another figure that is not considered to be particularly precise, with much variation between years. The diminishing breeding population is dwarfed by winter numbers, as you can read in this WaderTales blog, with increased attention being given to ways to afford better protection of red-listed, British-breeding birds.

January counts

blog BTThe paper in British Birds also includes a table of January population estimates, to provide data that are comparable to mid-winter counts in other countries. These figures are used in waterbird monitoring for the International Waterbird Census for the African Eurasian Flyway. The main table (and figures mentioned above) are average maximum winter counts (in the period September to March). Black-tailed Godwit is one species that illustrates the difference, with a mean of 30,000 in January and a mean peak count of 39,000. Having moulted in Great Britain, some Black-tailed Godwits move south to France and Portugal in late autumn, returning as early as February. January counts are therefore substantially lower than early-winter and late-winter counts. There is more about the migratory strategy employed by Black-tailed Godwits that winter in southern Europe in Overtaking on Migration.

Looking forward

blog BB coverThe authors have done a tremendous job. They have refined the way that estimates are calculated, they have combined the results from WeBS and NEWS III, and they have delivered population estimates for 25 wader species and many more other species of waterbirds. These population estimates will be used in conservation decision-making until the next set of numbers becomes available. Meanwhile, thousands of birdwatchers will count the birds on their WeBS patches in each winter month, every year. Without them, this paper could not have been written.

Before the next assessment, there will need to be another NEWS survey, to check up on species that use rocky and sandy shore birds, such as Purple Sandpipers, Turnstone and Curlew. Hopefully, there will also be a dedicated survey to assess Lapwing and Golden Plover numbers and perhaps we might find a way to refine the old estimates for Woodcock, Snipe and Jack Snipe.

Paper

Population estimates of wintering waterbirds in Great Britain. Teresa Frost, Graham Austin, Richard Hearn, Stephen McAvoy, Anna Robinson, David Stroud, Ian Woodward and Simon Wotton. Published in British Birds Volume 112. March 2019.

British Birds is a subscription journal. The issue containing this paper can be purchased separately. At some stage, the paper will become free-to-view.

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GFA in Iceland

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

@grahamfappleton

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From local warming to range expansion

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

Setting the scene

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

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

A booming population

godwit spread

Expanding breeding range in Iceland

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

blog chicks in nest

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

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

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

Catch your godwits

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

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

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

blog pete ruth

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

Major Findings

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

blog nest comparison

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

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

Are these findings applicable to other species?

blog cr juvenile

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

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

Paper

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

blog flock

Juveniles gather together in the late summer, prior to departure


GFA in Iceland

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

 

Designing wader landscapes

blog whimbrelMuch has been written about the negative impacts of agriculture on breeding birds – but farming can be good for some species. In Iceland, where high-input agriculture is relatively recent, breeding waders are commonly found in nutrient-rich environments that are associated with increased production. How can high breeding densities of waders be maintained, as farming continues to expand and intensification increases?

In her paper in Agriculture, Ecosystems & Environment Lilja Jóhannesdóttir investigates the distribution of breeding waders across landscapes with varying amounts of highly-cultivated fields and semi-natural areas. She discovers that, in some circumstances and at an appropriate level, adding cultivated land within a broader mosaic of habitats may benefit breeding waders. Is this a model system that provides clues as to how to design landscapes that can support sustainable breeding wader populations in other parts of the world?

The waders of Iceland

table

Breeding populations of waders in Iceland (AEWA report)

Iceland is a hot-spot for breeding waders, holding half or more of Europe’s Dunlin, Golden Plover and Whimbrel, in a country that is a bit smaller then England. The paper at the heart of this blog is written by Lilja Jóhannesdóttir, who worked with colleagues from the University of Iceland, the Agricultural University of Iceland, the University of East Anglia (UK) and the University of Aveiro (Portugal). They investigated how different ways of increasing agricultural productivity might impact upon these species, and others such as Black-tailed Godwit, Redshank and Snipe.

Much of Iceland’s upland interior is not suitable as farmland but there is still plenty of room for agricultural expansion. Only 7% of the area between sea level and an elevation of 200 m is currently under cultivation but it is estimated that it would be possible to increase this to 63% – an eight-fold extensification. Icelandic lowlands currently comprise a fine-scale mosaic of open semi-natural habitats and cultivated fields (primarily for silage production to feed animals), making most of the landscape much more heterogeneous than in countries with a longer history of commercial farming.

blog hay and semi-naturalTwo previous WaderTales blogs have already shown that:

Given that farm production is predicted to increase, that farmers like breeding waders and that some intensively-managed fields can be attractive to waders, is it possible to design farmed landscapes that will work for birds and farmers?

Increasing inputs and reducing heterogeneity

blog nice wetlandGlobally, the expansion and intensification of agriculture has altered landscapes and the associated homogenisation has greatly influenced bird abundance and reduced biodiversity. Populations of numerous species, particularly specialist species, have declined, as agriculture has expanded, while generalist species have often thrived in agricultural habitats.

There is no shortage of examples in which highly intensively managed farmland is shown to be bad for breeding waders. In the monoculture hay-meadows of the Netherlands, Black-tailed Godwit productivity is really low, for instance. These fields have been drained, fertilised and re-sown, in order to create easily-managed carpets of single-species grass that can be cut several times a year. There is more about this in this paper by Roos Kentie.

blog hay fieldAlthough there are some areas of Iceland in which farming is quite intensive, there are many others where farmers have a lighter touch. For instance, nutrient-poor dwarf birch marshes may occasionally be grazed by sheep in the summer but these areas have never received applications of artificial fertiliser. At this end of the intensification continuum, increasing agricultural operations may have benefits for breeding waders. When a patch of rough grazing is ploughed and turned into a hay meadow, the addition of fertilisers can potentially increase soil fertility and create an attractive place for waders to feed. A hay meadow within a local area that is dominated by dwarf birch marsh could effectively increase the heterogeneity (& nutrient-richness via spill-over) of the local area, albeit in an artificial way. In the UK, Golden Plovers breeding on moorland are known to travel up to 7 km to feed on fertilised hayfields with high earthworm densities. This paper by James Pearce-Higgins & Derek Yalden in IBIS provides a nice example of how low intensity agriculture can provide resources for waders in the wider landscape.

Researching waders and landscapes

blog dbmLilja’s work in the Southern Lowlands of Iceland focused upon understanding how agriculture influences breeding wader densities and how these relationships might influence future change. At its heart were counts of adult waders encountered along 200 transects (totalling over 100 kilometres) within semi-natural habitats, visited at several stages during the breeding seasons of 2011 and 2012.

As well as counting birds, Lilja categorised habitats within 500, 1000, 1500 and 2500 metres of the transects, which she called buffer area in the paper. Interestingly, and usefully for later analyses, the distribution of different habitat types is pretty uniform across these scales, in this part of Iceland, with little substantial difference according to elevation. In the diagram below, the 200 transects (a) have been split between those below 50 m above sea level (b) and those higher than 50 m (c).

buffers

Landscape-scale effects

To fulfill the various demands of parents and their offspring, waders need diverse resources on or near their territory. An adult can feed a kilometre or more away from its nest, between incubation bouts, and chicks are mobile from an early age. Tagging has shown that young Black-tailed Godwits can move up to 3 km in the first five days of life, just to give one example. In this open landscape, breeding success is likely to be a function of habitat availability at a broad scale. This is explored in a WaderTales blog about nesting Whimbrel.

blog redshankUsing data collected from these 200 lowland transects, Lilja was able to establish relationships between breeding wader densities and the amount of cultivated land and wetland in the surrounding landscape. These two habitat types were considered because future agricultural expansion is likely to take place on drained wetlands that have high conservation value. In her analyses she assessed the extent to which the amount of cultivated land in the surrounding landscape affects wader densities on semi-natural land, and then considered the potential effects of future agricultural expansion on wader populations. There was substantial variation in the density of all of the six most common wader species recorded on the transects, ranging from 0 to 284 birds/km2.

Lilja found that wader densities in semi-natural habitats were consistently greater when the surrounding landscapes had more wetland, at scales ranging from 500 m to 2500 m, indicating the importance of wetland availability in the local neighbourhood. However, the effects of cultivated land in the surrounding landscape varied with fertility and landscape structure, which was largely defined by altitude.

  • In fertile, low-lying coastal areas (from sea-level to 100 m altitude), wader numbers declined with increasing amounts of cultivated land (and the lowest densities occurred in areas dominated by cultivation). This suggests that further conversion of semi-natural habitats into farmland is likely to severely impact waders in low-lying areas.
  • In less fertile habitats at higher altitudes (between 100 m and 200 m), the lowest densities occurred in areas without cultivated land. This suggests that additional resources provided by cultivated land may have a more positive affect in the less-fertile, higher altitude areas.

blog blackwitThe relationships between the areas of wetland and agriculture in the surrounding landscape and the density of waders vary between species, as you can read in some detail in the paper. A few highlights are:

  • With increasing area of cultivated land, densities of Golden Plover, Dunlin and Whimbrel declined significantly at lower altitudes but increased at higher altitudes. These are the three species that would appear to respond most positively to the addition of pockets of cultivated land within a semi-natural matrix of less fertile land, that tends to be found at higher elevations.
  • Higher amounts of wetland were associated with increased densities of Dunlin and Black-tailed Godwit, but lower densities of Redshank. Golden Plover numbers were unaffected by amount of wetland in the surrounding landscape.
  • Whimbrel densities increased with wetland area, at higher altitudes. Wet patches have been shown to be very important to Whimbrel chicks, as you can read in this WaderTales blog about research in Shetland.
  • At lower altitudes, Snipe densities increased with the amount of wetland area in the local vicinity. This relationship was less pronounced at higher altitudes, which tend to be less effectively drained and hence generally wetter.

dunlin graphic

What now?

Changes in Icelandic landscapes are to be expected in the coming years, as most farmers intend to increase their areas of cultivated land. This expansion will inevitably have impacts upon the internationally important breeding wader populations of Iceland but the level of such impact will depend on where the expansion will occur. This paper shows that increases in the area of cultivated land at lower altitudes in Southern Iceland are more likely to result in declines in wader density than in less fertile areas, when tend to occur at slightly higher altitudes (still under 200 m above sea level). An important next step will be to identify the landscape structures and scales of management that can continue to support high densities of breeding waders.

blog coastal wetlandGiven the international importance of Iceland as a home for breeding waders it would be nice to think that this paper can be used to develop national land management policies that can prevent the unintended loss of species such as Golden Plover and Snipe, which landowners value and wish to preserve. At the farm and community level, the paper highlights the key importance of maintaining the complex and heterogeneous landscapes of lowland Iceland, retaining as many as possible of the remaining wetland patches and pockets of semi-natural land within even the most intensive of farming areas.

The paper may well be of interest to conservationists who are struggling to reverse wader declines in other parts of the world. In Southern Iceland, where 7% of the land is being farmed relatively intensively within a fine scale mosaic of both wet and dry semi-natural habitats, it is possible to support hundreds of waders per square km across the wider countryside. Can this situation be replicated across large tracts of land in other countries?

Take home message and paper

blog heterogeneousThis paper provides a useful reminder that the links between land use changes and biodiversity implications can be highly context-dependent. Further agricultural conversion of wetlands and rough grazing areas in the fertile low-lying areas of Iceland is likely to be detrimental for breeding waders, but such effects may be less apparent in less fertile, higher altitude areas. Here, the conversion of some land from rough-grazing to hay meadows may provide feeding opportunities off-territory for Dunlin, Golden Plover and Whimbrel. The scale at which the addition of cultivated areas is beneficial to breeding waders has yet to be determined.

This paper is published as:

Interacting effects of agriculture and landscape on breeding wader populations. Lilja Jóhannesdóttir, Jennifer A. Gill, José A. Alves, Sigmundur H. Brink, Ólafur Arnalds, Verónica Méndez and Tómas Grétar Gunnarsson https://doi.org/10.1016/j.agee.2018.11.024

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GFA in Iceland

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

 

Head-starting success

The first year of head-started Black-tailed Godwits

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Head-started bird from 2017

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

Success!

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

Earith 2

Where did the chicks go?

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

headstarted map

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

What about ‘wild’ birds?

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

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

Using geolocators

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

Mark release

Newly-tagged adult is released

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

The class of 2018

morgan 2018

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

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

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

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Funding

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


GFA in Iceland

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

 

 

Black-tailed Godwit and Curlew in France

In July 2018 there was a call for people to express their opinions on the issue of hunting Black-tailed Godwits and Curlews in France. This blog aimed to bring together some background to inform the discussion. The government decided to maintain the current situation until 30 July 2019: to shoot Curlew in some circumstances but to maintain a ban on shooting Black-tailed Godwits. There will be another review in the summer of 2019.

Problems for large waders

Oct 2017The Numeniini is the group of waders that includes curlews, godwits and the Upland Sandpiper. Globally this group is under threat – two species of curlew are probably already extinct. These long-lived species are threatened by pressures during the breeding season and, in some parts of the world, reduced annual survival.

Click here to read a blog about the threats to large waders.

Conservation of migratory species

The Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) is an intergovernmental treaty dedicated to the conservation of migratory waterbirds and their habitats across Africa, Europe, the Middle East, Central Asia, Greenland and the Canadian Archipelago.

Developed under the framework of the Convention on Migratory Species (CMS) and administered by the United Nations Environment Programme (UNEP), AEWA brings together countries and the wider international conservation community in an effort to establish coordinated conservation and management of migratory waterbirds throughout their entire migratory range.

Eurasian Curlew

RC picEurasian Curlews are listed as Near-Threatened by BirdLife/IUCN. Shooting of this species has ceased in western Europe, apart from France. A moratorium (pause) was put in place in France in 2008 but that was amended in 2012 to allow shooting on the coast, which is where many of the Curlews are to be found. Shooting of Curlews ceased in Great Britain in 1981, in Northern Ireland in 2011 and Ireland in 2012. The partial moratorium in France was extended until 30 July 2018 and then to 30 July 2019.

LPO (Ligue pour la Protection des Oiseaux), the BirdLife International partner in France, argue that shooting of Curlew should cease or at least that that there should be another moratorium, for at least three years, covering coastal as well as inland areas.

Jan 2018 extinction riskAn AEWA (Agreement on the Conservation of African-Eurasian Migratory Waterbirds) plan of 2015 called for an immediate end to hunting and for an Adaptive Harvest Management process to be set up to recommend if any hunting could be sustained. Continuedcurlews in france shooting in France must surely be in contravention of the international plan? Here’s a link to the AEWA Action Pan for Eurasian Curlew.

Tens of thousands of Curlew spend the winter in France, migrating here from across Northern Europe. The purple dots on the map alongside represent the recovery locations of Curlew ringed in Britain and Ireland. Many of these ringed birds have been found in breeding areas, especially Finland, but there are plenty of reports in coastal France, most of which are birds that have been shot.

Click here to read a blog explaining why we should be worried about Curlews.

Black-tailed Godwit

subspeciesTwo subspecies of Black-tailed Godwit spend time on French estuaries; limosa and islandica. The size of the islandica subspecies is increasing, as the breeding range in Iceland expands (blog about this) but the number of limosa is in rapid decline. Limosa birds that spend time in France breed in the Netherlands and surrounding countries, including a small number that breed in the washes of East Anglia. You can read about the 75% decline in the Dutch breeding population in this blog.

Picture7Agreements signed by partners of AEWA and members of the European Union included a five-year moratorium (pause) in shooting of Black-tailed Godwits in the whole of France. This was extended for a further five years, up until 31 July 2018 and then for one more year, until 30 July 2019.

It is hard (or even impossible) to separate islandica from limosa Back-tailed Godwits and we know that they occur in mixed flocks. Scientists have been colour-marking Black-tailed Godwits of both subspecies for many years and birdwatchers can help to assess the relative threat to limosa by reporting colour-ring sightings. You can read more about the value of colour-ring sightings here:

Godwits & Godwiteers 

Project Godwit

blog ManeaBlack-tailed Godwit is still on the French quarry list but there is an ongoing hunting moratorium (pause) that, as for inland Curlew, ended on 31 July 2018 but was extended to 30 July 2019.

LPO argue that, given that it is not possible to distinguish the two subspecies, Black-tailed Godwit should be removed from the quarry list or, alternatively, that there should at least be another moratorium (of at least three years).

Result of the consultation

As indicated at the start of this blog, a decision was made in July 2018 that nothing would change for another year. There would be a complete ban on the hunting of Black-tailed Godwit in France until 30 July 2019 and permission was granted to continue to hunt coastal Curlew. Link here.

Evidence is being collected by conservation scientists that will hopefully inform the decisions that are made as to what should happen after 30 July 2019.


GFA in Iceland

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

Site-fidelity in Black-tailed Godwits

Shorebirds are generally philopatric (site-faithful to breeding areas) – youngsters settle to breed in areas near where they were raised and adults don’t move far in subsequent years. What happens to this process when a species is expanding its range or if chicks are reared away from their parents?

Successful head-starting

In a recent trial, to see if head-starting might help to secure the future of limosa Black-tailed Godwits in the Washes of Eastern England, one of the questions to be answered was “would youngsters reared in captivity be able to gather all of the information they need to return to the same area to breed?”

blog nestEggs collected from nests on the RSPB’s Nene Washes nature reserve were taken to the WWT’s facilities at Welney, about 35 kilometres away, to be head-started. Here, the eggs were hatched and the chicks were raised in captivity. As they got bigger, the birds were colour-ringed and moved into a large pre-release cage before being given their freedom, when old enough to fly. With 26 successful head-started chicks, this process added far more young Black-tailed Godwits to the local population than birds in the wild could manage, subject as they were to predation and to flooding of nests. You can read more on the Project Godwit website and in this WaderTales blog Special Black-tailed Godwits.

Limosa Black-tailed Godwits migrate south for the winter, most flying to countries such as Senegal in West Africa but with an increasing number short-stopping in Spain and Portugal. (There’s a blog about the wisdom of crossing the Sahara).

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In this picture of three head-started chicks, Remi is the chick on the right

As birds moved north in the spring, Project Godwit staff were on the look-out for the previous year’s chicks. They were overjoyed when the first of these appeared at Welney, as had been hoped and might be expected, but puzzled when the second was sighted in Doel, near Antwerp in Belgium, showing signs of pairing with what was assumed to be a local, unringed male. So, what had happened to site-fidelity? Why had this colour-ringed female, named Remi, decided to settle over 300 km away? What are the implications for the project to boost the East Anglian population?

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Sites mentioned in this blog. Remi was collected (as an egg) in the Nene Washes, raised at Welney and turned up next spring in Doel, Belgium. Friesland is Roos Kentie’s study area (see below).

Philopatry in Black-tailed Godwits

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Manea – all grown up and back on the Ouse Washes

The head-starting team had been fairly confident that site-fidelity would ensure that head-started birds would recruit locally, as long as the hand-rearing process did not mess with the innate processes that initiated recruitment.

A paper based on ringing recoveries of the limosa subspecies in The Netherlands, published in 1998 by Kruk et al, suggested that young Black-tailed Godwits tend to settle to breed close to where they previously fledged, with most moving no further than 6 km and no appreciable difference between the sexes.

Natal philopatry in the Black‐tailed Godwit L. limosa limosa and its possible implications for conservation, Ringing & Migration, 19:1, 13-16, DOI: 10.1080/03078698.1998.9674156

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The expanding range of breeding Black-tailed Godwits within Iceland

In Iceland, where the islandica population of Black-tailed Godwits breeds, colour-ringing of chicks has also allowed dispersal patterns to be measured. Here, youngsters of the islandica race are still pretty site-faithful but there are appreciable differences between the two sexes, with some females dispersing far more than males. In their paper published in 2011, Tómas Gunnarsson et al found that males dispersed an average of 2.3 km (with a range of distances of 0.5 to 7 km) and females dispersed an average of 48 km (with a range of 1 to 204 km). As has been discussed in a previous WaderTales blog, Icelandic Black-tailed Godwit numbers have been increasing for a century, with birds moving into new breeding areas further away from the heartlands of the south coast. Dispersal is a necessary part of the expansion process. There’s more detail here:

Rapid changes in phenotype distribution during range expansion in a migratory bird. Proc. Royal Soc. B, 279:1727 (2011). DOI: 10.1098/rspb.2011.0939

postThe conservation problems being faced by limosa Black-tailed Godwits have spawned a lot of recent research in The Netherlands and along the subspecies’ annual migration route (see Dutch Black-tailed Godwit numbers down by nearly 75%, for instance). In a recent paper, Roos Kentie showed that three-quarters of the adults in her Friesland study site in The Netherlands breed within 500 m of their previous nest site, with a maximum movement of 15 km. Having successfully fledged and migrated south and then north, new recruits settled within 18 km. As in the previous paper about the limosa subspecies, there was no discernible difference between the distances moved by males and females, but there were differences in mean dispersal distances of youngsters raised in different habitats. Birds hatched on grass monocultures moved about twice as far as those from herb-rich meadows, but the mean distances were only 915 m and 1700 m for the two habitats. Young birds moved at a higher rate from the predominant monocultures to meadows than the other way around.

Age-dependent dispersal and habitat choice in black-tailed godwits across a mosaic of traditional and modern grassland habitats Journal of Avian Biology 45: 396–405 (2014). DOI: 10.1111/jav.00273

If limosa Black-tailed Godwits recruit to local sites then what was Remi, the head-started bird from the Washes of eastern England, doing in Belgium? Does this failure to be site-faithful impact upon the conservation programme that aims to boost local populations through hand-rearing and releasing chicks?

Back to the Belgian defector

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Protecting nesting waders by setting up electric fences

By early May, five of the Project Godwit head-started Black-tailed Godwits (three males and two females) had been seen on the Ouse Washes, at Welney and other sites. This was excellent news and in line with what might be expected, given that the Dutch study has shown that only 30% of recruitment is in the first summer, with most birds not starting to breed until their second year. No birds had returned to the Nene Washes, where these eggs had been laid. In terms of site-fidelity, this is what had been expected. It was great news; head-starting works and can give a conservation boost for the species in areas where insufficient young are produced to maintain local populations. It may therefore be possible to reintroduce (or even introduce) Black-tailed Godwits to suitable sites, simply by releasing hand-reared fledglings when they are ready for their independence.

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The Nene Washes

And then came number six. On 6 May, another of the ringed, head-started birds was seen on the Nene Washes, just a short distance from where the eggs had been collected. She was ‘home’ but did not know it, having been transported 35 km to Welney when in the egg. Amazingly, this bird turned out to be Remi, the female that had been consorting with a male in Belgium three weeks earlier. She was with an unringed male, a bird that members of the Project Godwit team felt looked ill-at-ease, not as accepting of their vehicles as were local birds. Perhaps Remi had acquired her mate in Belgium and brought him with her to England? If so, wouldn’t that be a result – this head-started Black-tailed Godwit had not only returned to breed but she might also have brought an extra bird with her!

Remi's chicks

In terms of site-fidelity, Remi fits with the patterns discussed above; she has not moved very far from the site she knew as a fledgling, as suggested by the studies of limosa birds, but she has dispersed further than any of the males, in line with the islandica study. It will be interesting to see what happens to subsequent groups of head-started birds.

** Fantastic update from Project Godwit **

“Delighted to share news that Remi, released last year at WWT Welney, now has chicks of her own at RSPB Nene Washes! Godwits don’t usually breed in their first year and we hope this is the first of many” 14 June 2018

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For the latest news of the head-starting project, check out projectgodwit.org.uk or follow @projectgodwit on Twitter.


 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

 

 

Just one Black-tailed Godwit

When you receive a list of sightings of a colour-ringed bird that you have reported to a scheme organiser, it can hide a wealth of information. Here’s one such bird.

Blue Red – Yellow Green-flag

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BR-YGf photographed in Caithness (north of Scotland) in the spring of 2017

There are some colour-ringed Black-tailed Godwits that have generated two hundred or more sightings at well-watched locations but BR-YGf is more typical. When seen in Cambridgeshire on 26 March 2018, that was only the 12th observation in the database.

The Black-tailed Godwit that was soon to become BR-YGf was wintering in Portugal when caught in a mist net, by José Alves and a team of other ringers, just before dawn on 25 October 2014. It was given a unique set of three colour-rings and a flag, that would enable it to be identified in the field by birdwatchers. Measurements of wing length and bill length, taken at the time, meant that it could be identified as a male, using criteria described in this paper in Bird Study.

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Wader-ringing team in Portugal

Colour-ringing of Black-tailed Godwits started in Portugal in 2006, when José was working on a PhD at the University of East Anglia, in which he studied the ecology of Black-tailed Godwits wintering on the Tagus and Sado Estuaries of Portugal. Colour-ringing has continued since, contributing to coordinated studies of Icelandic Black-tailed Godwits in Spain, Portugal, France, the UK, Ireland and, of course, Iceland.

Breeding in Iceland

Almost all of the islandica Black-tailed Godwits breed in Iceland, with small numbers on the Faeroes, a handful on the Lofoten Islands of Norway and an occasional breeding pair on a Scottish island. Jenny Gill and I saw BR-YGf in the west of Iceland in April 2016, as we checked for marked birds in a flock of 1100 birds, many of which were new arrivals. He was feeding in a newly-ploughed cereal field, that had been previously spread with pig-muck from the neighbouring industrial-scale piggery. We managed to look at 800 pairs of legs in that flock; there was another green-flagged bird from Portugal, two orange-flags from France, a bird from Ireland and three from England.

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The history of BR-YGf since he started wearing coloured rings in 2014

We have been checking flocks of Black-tailed Godwits arriving in Iceland for many years. One of the most significant recent outputs is a paper that explains that young birds, recruiting into the population, are driving the advancing arrival of the species into Iceland in spring. The results are summarised in this blog: Why is spring migration getting earlier?

Autumn moult

Most of the Icelandic Black-tailed Godwits that winter in Portugal stop off to moult en route in autumn. We see some of these birds in the UK but BR-YGf is one that, from the sightings in September 2016, probably moults into winter plumage in France. Moulting is an energetically expensive process; birds that are mid-moult don’t usually migrate so these autumn staging sites are very important to the flocks that use them. When first caught in Portugal, in late October 2014, BR-YGf was in full winter plumage, probably having recently arrived from France.

Spring overtake

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The Samouco salt-pans, where BR-YGf was ringed, with Lisbon in the background

Portugal is a warm place to spend the winter, with relatively long days and plenty of food – very different to the east coast of England, for instance. The only down-side is that Portugal is a long way from Iceland, which you might think leads to later return in the spring. Most Portuguese birds get around this problem by migrating in two legs, the first of which takes them to either the Netherlands or the British Isles. BR-YGf chooses the British option. This blog explains this migratory strategy: Overtaking on migration.

BR-YGf has been spotted in two springs since ringing. On 14 March 2016 he was seen at Old Hall Marshes in Essex by Steve Hunting and on 26 March 2018 he was seen by the Project Godwit team on the Nene Washes in Cambridgeshire. Mark Whiffin and colleagues were looking for limosa subspecies godwits, newly returned from Africa to breed, but their birds were outnumbered by large flocks of islandica, fattening up for the trip north. There’s more about the differences between the two subspecies in Godwits in, godwits out: springtime on the Washes with some hints on distinguishing which subspecies is which.

Portuguese birds, on an earlier migratory schedule, tend to be further ahead, in terms of moult, standing out in their red finery against the greyer local birds, some of which will travel to Iceland up to four weeks later. You can read more about the spring moult in this WaderTales blog: Spring moult in Black-tailed Godwits. Did you know that waders smell different in summer plumage?

Why Caithness?

BR-YGf has been following a well-used migration route: breed in Iceland, moult in France, winter in Portugal, spring in England, back to Iceland and repeat, for perhaps twenty or more years. What was he doing in Caithness, in the very far north of Scotland on 22 April 2017?

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Although the average timing of arrival of individual godwits in Iceland has not changed, the small amount of annual variation in their timings may be related to the weather they encounter en route. In the spring of 2017, we were in Iceland waiting for birds to turn up. The weather was lovely – if cold – but northerly winds appeared to bring a brief halt to most migration. In our two-week stay we saw only 28 colour-ringed Black-tailed Godwits; not quite as bad as the spring of 2013, when winter returned to Europe in April, but close.

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In some years, Black-tailed Godwits, and other waders making the trip to Iceland, may get part way across the Atlantic and have to turn back or they may reach the north of Scotland or the Western Isles and stop. Colour-ring sightings alert colour-ring coordinators to these events, as presented in the blog: Waiting for the wind.

Thank you

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Looking for Black-tailed Godwits in Moita (Portugal) – José Alves, Jenny Gill and me

Thousands of birdwatchers have contributed to the studies of Icelandic Black-tailed Godwits. Every sighting is valuable, especially repeat records from the same site. This WaderTales blog tells the stories of some of the birdwatchers who contribute their sightings to these projects: Godwits and Godwiteers.

It’s great to see old friends, when out ‘godwitting’. Jenny Gill and I have seen BR-YGf in Portugal (2016 & 2017) and in Iceland (2016). We recognised him but he probably will not have recognised us.

Please report any colour-ringed Black-tailed Godwits to j.gill@uea.ac.uk and she will forward them to the appropriate coordinator as necessary. Thank you!


 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

 

Waders are long-lived birds!

The BTO longevity record for a wader is held by an Oystercatcher that was ringed as a chick by Adrian Blackburn in Lincolnshire (east coast of England) on 14 June 1970 and last caught by the Wash Wader Ringing Group on 16 July 2010, in virtually the same bit of the county. The time between ringing and last capture was 40 years 1 month and 2 days. Perhaps the bird is still alive?

Redshank

Will this Redshank live for another 10, 20 or 30 years?

Just to put records for British & Irish waders into context, the record for seabirds was set by a Manx Shearwater, at 50 years 11 months and 21 days, for waterfowl it’s a Pink-footed Goose (38 years 7 months and 7 days) and the longevity record for a passerine was set by a Rook (22 years 11 months 0 days).

This blog summarises records from the BTO Ringing Scheme between 1909 and 2017. These longevity records might be useful for a bird club quiz but they tell us very little about the health of wader populations. The real thing that is of interest is survival rates. Measuring the proportion of adult birds that survive through until the next year turns out to be exceptionally important to our understanding of wader conservation. There will be more about this later.

Records from the BTO scheme

2017 tableThe list of records alongside is taken from the Online Ringing Report, produced by the British Trust for Ornithology. (The link to the longevity records can be found at the bottom of the web-page). The report covers all birds ringed and/or reported in Britain & Ireland up until the end of 2017. I aim to update this blog shortly after each new annual report is published.

For each species, longevity is defined as the time between ringing and the most recent report of that bird. For a chick, this figure is virtually equivalent to age but a bird first ringed when already an adult may be many years older than the longevity figure. The third column is the number of birds ringed for each species (up to the end of 2016). Records for species of which fewer than 3000 individuals have been ringed are given in italics, to indicate that the small sample size might be affecting the longevity record. With fewer birds being handled, the chance of catching a bird that is going to live a long time is low, as is the chance of it being caught again many years later.

In common with most groups of birds, the longest-lived ones are the biggest. Only Oystercatchers, Curlews and Bar-tailed Godwits have so far broken the 30-year barrier. At the other end of the scale, for smaller species, only the Ringed Plover has reached 20 years.

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Grit wears even the hardest of metal rings (Richard Chandler)

With the passage of time, two things get older, the bird and its ring (or three things, if you think about the age of the ringers). Early rings were made of alloys of aluminium and these deteriorated quite rapidly, especially in salt water. Many of these rings will have given up long before the birds that were ringed. The widespread introduction of harder alloys in the 1970s has helped to increase longevity records.

Species such as Turnstone still wear out their rings and the oldest Oystercatchers are often birds that have carried two or more rings during the course of their lives. Such replacements only take place in areas where long-term studies are taking place, as was the case for the 40-year-old Oystercatcher mentioned above. It was first ringed as SS58540 but also known as FC15938 and FP99170.

FrenchAnother factor affecting our ability to appreciate just how long a wader can live is the use of colour-rings. The record-breaking Black-tailed Godwit is currently EF90838. This bird was hatched from an egg in Iceland in 1977 and received a metal ring on 24 October that autumn, at Butley in Suffolk. Many east-coast Black-tailed Godwits moult on the Wash (between Lincolnshire and Norfolk) and this bird was caught there in 1993. Already 16 years-old, it received two colour-rings that identified it as a bird taking part in a new Wash-based study, but not as an individual. In 1996, it was caught on the Wash again and given an individual set of rings. It was never caught again but was seen many, many times – most recently on 12 April 2001 by the late John Parslow.

Getting old

oldestThe annual renewal of a wader’s feathers enables an unringed individual wader to hide its age. The picture alongside was taken by Allison Kew, of the Wash Wader Ringing Group. This ringed Oystercatcher was well into its thirties at the time – older than any of the people in the photograph.

If still alive then a bird will migrate and attempt to breed in the same way as in the previous year, repeating the process for decades. Senescence probably kicks in eventually; there is some evidence of lower annual survival and reduced breeding success at the upper end of a species’ life-span. Long-term colour-ringing will enable this topic to be explored further in due course.

Survival

As mentioned earlier, although the longevity of a species might tell us something about annual survival rates, in that birds with high longevity almost certainly have the highest survival rates, being able to measure the proportion of adult birds that survive from one year through to the next is far more valuable.

Blog adultWaders adopt a ‘high-survival and low breeding-output’ strategy. Most waders have an annual survival rate of between 70% and 90%. This means that a pair of Lapwings, for instance, only needs to raise an average of 0.7 chicks per year to maintain a stable population. Unfortunately, this is not easy to achieve, as you can read here.

The occasional good breeding season can give a real boost to population levels, as we saw for Icelandic Black-tailed Godwits in the summer of 2017, as you can read here.

By collecting records of colour-ringed birds it is possible to measure the annual survival rates of wader populations, as explained here in this blog about Bar-tailed Godwits.

great knotWhen survival rates drop, the effect on population levels is immediate and dramatic, as discussed in this blog about the waders that use the Yellow Sea. Populations of Bar-tailed Godwit, Red Knot and Great Knot that winter in Australia and New Zealand were particularly badly affected by habitat removal, leading to a sudden drop in survival rates and rapid declines in numbers.

There is a global review of survival rates in this paper: Méndez, V., Alves, J. A., Gill, J. A. and Gunnarsson, T. G. (2018), Patterns and processes in shorebird survival rates: a global review. Ibis. doi:10.1111/ibi.12586. The paper is summarised in this WaderTales blog: Measuring shorebird survival.

Please help to measure survival rates

The chance of finding a ringed bird that breaks a current longevity record is tiny but every birdwatcher who reports a colour-ringed wader is helping to monitor survival rates. If you have ever done so – thank you.

 


 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

 

 

 

 

 

Farming for waders in Iceland

Across the world, agriculture is one of the primary threats to biodiversity, as we tear up natural environments to create more space to feed an ever-growing and increasingly meat-hungry human population. Agricultural land can, however, also provide key resources for many species whose behaviours align with the rhythms of the farming year.

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In Iceland, farming areas support large and important populations of several wader species, including 75% of Europe’s Whimbrel and over half of Europe’s Dunlin. As the country welcomes more tourists and expands the range of crops grown for food and fuel, what might be the implications for iconic species such as Whimbrel, Dunlin and Black-tailed Godwit?

This paper by Lilja Jóhannesdóttir, of the University of Iceland, and colleagues there and at the universities of Aveiro (Portugal) and East Anglia (UK), investigates the use of farmland by waders living in a semi-natural landscape.

Paper details: Use of agricultural land by breeding waders in low intensity farming landscapes Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill, & Tómas Grétar Gunnarsson Animal Conservation. doi:10.1111/acv.12390

A dynamic landscape

blog snipe postIn Iceland, volcanic activity poses serious short-term threats to agriculture, especially in areas close to the mid-Atlantic ridge, which runs through the island from south-west to north-east. Threats from volcanoes include ash-fall, lava, flooding of glacial rivers and earthquakes but, on the plus side, nutritional inputs from volcanoes have beneficial effects on soil fertility in these central areas. Over time, and with the assistance of wind and water, many of these nutrients collect in the lowlands of the country – the areas that now form the main agricultural areas, especially in the warmer south.

The distribution of breeding waders varies across lowland Iceland. A survey carried out between 2001 and 2003 showed that wader densities were greater in areas of the country that had been subject to higher rates of volcanic ash deposition with, for instance, three times as many waders in the south as in the west. See How volcanic eruptions help waders. As was shown in the paper at the heart of that blog, the nutrient signal associated with ash-fall breaks down in farmland. Here, perhaps as a consequence of the application of natural and artificial fertilisers over decades or even centuries, there is no association between ash-fall and wader density. Across the whole country, irrespective of the proximity of volcanoes, nutrient-rich agricultural land attracts waders – but which wader species and across which farmland habitats?

Waders and agriculture

In a previous paper, Lilja Jóhannesdóttir showed that over 90% of Icelandic farmers think it is important or very important to have rich birdlife on their estates, but that farmers also expect to increase the area of farmed land in the coming years. There’s more about this in the WaderTales blog: Do Iceland’s farmers care about wader conservation? It is important to understand the ways that waders currently use farmland, in the hope that nesting waders can continue to be accommodated within the future farming landscape of Iceland.

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Perhaps Oystercatchers think that the fields have been ploughed especially for them?

Agriculture in Iceland is still relatively low in intensity and extent, and internationally important populations of several breeding bird species are abundant in farmed regions. Only about 2% of land is cultivated (about 7% of lowland areas), of which about 85% is hayfields (grass fields managed to produce crops of grass for storage as winter feed) and 15% consists of arable fields (mostly barley). This is similar to areas such as Norway, northern Canada and northern and western areas of the British Isles but contrasts sharply with the US and many countries in the EU which, on average, have 20% or more of their land under cultivation.

In these high-latitude landscapes, agricultural land can potentially provide resources that help to support wader species. To address these issues, Lilja conducted surveys of bird abundance on 64 farms in northern, western and southern areas of Iceland that vary in underlying soil productivity, and quantified:

  • Levels of breeding bird use of farmed land managed at three differing intensities, ranging from cultivated fields to semi-natural land
  • Changes in patterns of bird use of farmed land throughout the breeding season.

Farm survey

In Iceland, there are still large patches of natural or semi-natural habitats; they surround the hay-fields and arable fields that are at the heart of many farms. This arrangement creates gradients of agricultural intensity from the farm into the surrounding natural land, tapering from intensive management to moderate and light management.

BLOG gradient

The three intensity levels within Icelandic farmland can be roughly described as follows:

  • Intensive: Hayfields (85%) and arable fields (15%) fields. Most hayfields are mown twice per year and ploughed and reseeded every few years.
  • Moderate: Old hayfields that are rarely or never mown but are used for grazing, or fertilized grasslands used for livestock grazing.
  • Light: Semi-natural or natural areas under low intensity grazing, usually by sheep or horses, or with no agricultural influence, ranging from sparsely vegetated habitats to habitats with abundant vegetation (where grasses and bushes dominate the vegetation) and with a broad wetness gradient.

Fields corresponding to these three categories were surveyed on the 64 farms, firstly during the egg-laying and incubation period and then later, to coincided with chick rearing.

blog 3 habitats

Gradient of management from intensive (left) to wet semi-natural (right)

Where were the waders?

blog RK on postLarge numbers of waders were encountered in all transects in all parts of Iceland, with Black-tailed Godwit and Redshank contributing most records. There were also important numbers of Oystercatcher, Golden Plover, Dunlin, Snipe and Whimbrel. Overall, wader densities on farms did not vary significantly between regions or between early and late visits but there were some subtle differences:

  • Wader density varied significantly along the management gradient, with lower densities tending to occur in more intensively managed areas, particularly in the early (nest-laying and incubation) season.
  • Intensively managed fields in the west (where underlying soil productivity is lower) had higher densities of waders than in the north and south of the country.
  • There were seasonal declines in wader density on all three management types in the south, but seasonal increases on intensive and moderate management in the west and in fields under moderate management in the north.
  • There were some differences between species in these patterns (more details in paper).

blog redshank westOne of the interesting differences in the west was the redistribution of Redshank as the season progressed. There were three times as many pairs of Redshank in cultivated land during the chick-rearing period than during incubation, suggesting that adults may be moving broods into cultivated land. Resources for chicks may well be relatively more abundant or accessible in these areas, given the relatively low levels of nutrients in areas that are a long way from the active volcano belt. There’s also a suggestion that drainage ditches around cultivated fields in the west may provide important resources for Snipe.

What about the future?

blog distributions

Wader densities during the early (red) and later (blue) part of the breeding season (Modified from the paper in Journal of Animal Conservation)

Although the density of birds in Iceland’s agricultural landscapes tends to be higher in lightly managed than intensively managed agricultural land, densities in the areas under the most intense agricultural management are still high, suggesting that agricultural habitats provide important resources within these landscapes (see figure alongside). These density estimates (between 100 and 200 waders/km2) are typically much higher than those recorded in other countries in which these species breed.

Farmers in Iceland expect to expand their cultivated land in the coming years in response to increasing demand for agricultural production (Do Iceland’s farmers care about wader conservation?), and evidence from other countries throughout the world has shown how rapidly biodiversity can be lost in response to agricultural expansion and intensification. Protecting these landscapes from further development is crucial to the species that they support.

The authors suggest ways in which farming practises might change wader distributions in Iceland. Here are a few of the interesting points that they make:

  • When wader-rich semi-natural land is replaced by arable farming and intensively-managed hayfields, this is likely to reduce overall wader densities.
  • Losing wet features, which provide insect food for waders, may well have impacts for chick growth. Here’s a WaderTales blog that discusses the importance of wet features to Lapwings in the UK.
  • In other countries, early grass mowing is a direct threat to nests and chicks. Clutch and brood losses are already being observed in Iceland and, with warmer springs encouraging earlier grass growth, this could become more of a problem.
  • The conversion of less-intensively managed areas into farmland is likely to have most effect on Dunlin, Black-tailed Godwit and Whimbrel, which tend to occur in their highest densities in the least intensively managed lowland areas.

blog walk WhimbrelIt is estimated that between 4 and 5 million waders leave Iceland each autumn, for Europe, Africa and the South Pacific (Red-necked Phalarope). Iceland’s farmland supports many of these birds and this study highlights the need to protect them from the agricultural developments that have led to widespread wader losses throughout most of the world.

You can read the paper here

Use of agricultural land by breeding waders in low-intensity farming landscapes Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill, & Tómas Grétar Gunnarsson. Animal Conservation. doi:10.1111/acv.12390

blog oycs & chick

 


 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

 

 

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.

Blog RINGOS

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

WeBS70logo6a_smallThe 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, I highlight seven WaderTales articles that use WeBS data. Click on the links in bold if you want to read a particular story.

Curlew counts

curlew

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.

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 Oystercatchers

L17A9623 (2)

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.

oyc webs

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

Mid-winter movements

figureThe 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.

National patterns and local counts

blogGroups 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

horse-and-flockEvery 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. T with BTGA 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

NEWS tableThe 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 initial assessment of the results for NEWS-III in the latest WeBS report and I look forward to writing up the results as a WaderTales blog, once a paper is published.

Links to blogs mentioned already

Many more to choose from

There are over 40 WaderTales blogs to choose from in this list. Four of these articles might be of particular interest to WeBS counters:

  • knot

    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. sum plum
  • 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.

Thank you

Blog Counter 1I 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.


 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