Dutch Black-tailed Godwit numbers down by nearly 75%

Colour-rings and radio-tracking are helping to chart the ongoing decline of the Dutch Black-tailed Godwit population.

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A Portuguese rice field, full of limosa Black-tailed Godwits; most are Dutch breeders

The Black-tailed Godwit is the national bird of the Netherlands, the country in which the vast majority of the West European limosa race breed. These Dutch birds are an important part of the country’s cultural heritage and are of major international significance. Large amounts of money have gone into supporting the species, and the meadows that they share with others such as Redshank and Snipe, but efforts so far have failed to reverse a Black-tailed Godwit decline that has been going on since at least the 1970s. This negative situation is in stark contrast to the increases seen in the islandica subspecies that breeds in Iceland and winters in countries between Scotland and Spain. (There’s a comparison of the two subspecies in this WaderTales blog)

Counting Black-tailed Godwits

vero-pretty-flockIt is often easier to measure changes in numbers of waders on the wintering grounds, when birds are in flocks, than when pairs are thinly spread across their breeding ranges. For Dutch Black-tailed Godwits, most of which spend the winter in African countries, south and west of the Sahara, however, the best opportunity to monitor population trends occurs in Spain and Portugal in February, when the birds are on their way back to breed.

Each year a small group of ornithologists visit key sites in Extremadura, the Doñana Wetlands and the rice fields of the Tagus Estuary, to count flocks of birds and to look for colour-ringed birds. They’re able to use these counts and sightings of colour-ringed birds to assess what has happened to numbers in the previous twelve months.

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grutto met ringen (ringed Black-tailed Godwit)

In three of the years since 2007 they’ve witnessed increases but in most years the numbers have gone down. As February 2017 approaches, what will this year’s score be? How many of last year’s birds will have died and how many chicks hatched in 2015 and 2016 will be making the migratory journey north for the first time?

When assessing how many breeding godwits there are in the Netherlands the researchers collect and use the following information:

  • Counts of birds seen in flocks in Spain and Portugal.
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    It’s not always easy to see the colour-rings in rice fields

    Counts of colour-ringed birds. There’s a great one-line comment in the newly-published paper that forms the basis of this blog: ‘In total, we checked 420,206 godwits for colour-rings at Spanish and Portuguese staging sites’. That’s a lot of legs – and a huge effort.

  • An assessment of the proportion of islandica Black-tailed godwits in the flocks, so that they can be removed from the estimation process. This proportion had been established previously but were also monitored using sightings of colour-ringed birds of the islandica and limosa subspecies, and by taking account of the proportion of each population that wears rings.
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    Rosemarie Kentie in the rice fields of the Tagus estuary (Portugal)

    An estimate of the number of the birds that will be flying north to the Netherlands, as opposed to other countries. Limosa Black-tailed Godwits that pass through Iberia are on their way to a range of countries, stretching from the tiny population that breed in the UK, in the Ouse and Nene Washes, across to Germany in the east. This proportion was calculated by monitoring the movements of satellite-tagged individuals.

The results have just been published in a new paper, which also presents annual survival rates, obtained using colour-ring sightings. There is a full explanation of the methodology in the paper. You can also see maps from the satellite-tagging project on the King of the Meadows website.

postEstimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites. Ardea 114: 213–225. doi:10.5253/arde.v104i3.a7

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.

Latest findings

Over the eight years of the survey work, the average decline in numbers of limosa Black-tailed Godwits has been 3.7% per year. Numbers appeared to go up between 2009 and 2011, when the calculated survival rate of young birds was high, but the magnitude of this perceived recovery may have been artificially elevated by an increase in the number of Icelandic birds. From WeBS counts in the United Kingdom, the number of islandica birds is continuing to rise.

Since 2011, the estimated annual decrease has been 6.3% per year. Such large declines can only occur if there is both low recruitment and reduced adult survival.

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Agricultural intensification has seriously affected Dutch Black-tailed Godwits

The estimated breeding population in the Netherlands in 2015 was 33,000 pairs, representing a drop of nearly 75% since 1967. However, the agricultural grasslands of the Netherlands are still the single most important stronghold for breeding limosa  Black-tailed Godwits using the East Atlantic flyway.

The authors finish with a sad conclusion. “Although enormous amounts of money and effort have been expended to conserve continental godwits, our findings make clear that these have been ineffective or insufficient.”

One wonders how much worse the situation would have been without Dutch and European support for Meadow Birds and the ‘King of the Meadows’ in particular?


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Estimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites.  

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.


 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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Wales: a special place for waders

From winter beaches to summer moorland and woodland, Wales provides essential habitats for waders. 

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

Winter beaches & estuaries

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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 Bar-tailed Godwits from Siberia to Turnstones from Canada. 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. They emphasise the close links between Wales and Iceland when it come to birdlife.  Migratory decisions for Icelandic Oystercatchers explains how a new project is examining the costs and benefits of being a migrant. Welsh reports of Icelandic colour-ringed birds are helping to provide answers.

snipe-1Interestingly, while there are similar links between Ireland and Iceland, the migratory provenance of Welsh Snipe may 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.

Protecting key wintering sites is a high priority when it comes to wader conservation. A recent BTO and WWT project aims to provide better information as to how species as diverse as Dunlin and Shelduck make use of the Severn Estuary. This is important work, with major relevance to discussions as to how power might be generated within the estuary. Tracking waders on the Severn urges birdwatchers to look for colour-marked birds. Initial results, shared at the recent International Wader Study Group conference, indicate that the home range of a Redshank is ten times as big as originally thought. It will be interesting to see what else this study reveals.

horse-and-flockHundreds 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 sites 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. I had not realised that 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.

Passing through

whimbrel-mig-fig1There 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 recent 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.

Breeding Waders

Wales provides homes to many breeding waders, from Ringed Plover on the coast, via Little Ringed Plover and Commons 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.

CattleStarting 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 area any less careful as to where they put their feet. There are several other blogs about Lapwings and Redshank on the WaderTales site.

We are all aware of the issues facing upland waders. The next blog was written to promote a survey in England, looking at the distribution of waders along the moorland/farmland interface, but the stories will have resonance with Welsh birdwatchers. All downhill for upland waders outlines changes to breeding numbers and distributions of waders breeding in England’s uplands.

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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 RSPB, BTO, GWCT and BirdWatch Ireland are focusing on this species How long will it be until breeding Curlew are lost from Wales, completely?

Predation is acknowledged as a major issue for Curlew but is this going to be 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. There’s a specific mention of the Burry Inlet control programme of the 1970s.

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 latest 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 40 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.


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

Can habitat management rescue Lapwing populations?

Can a mosaic of habitats boost hatching success in grassland-breeding Lapwings?

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Lapwings are becoming more and more restricted in their distribution within the United Kingdom, with an increasing proportion dependent on a small number of lowland wet grassland sites, particularly nature reserves. Working in this habitat, a team from the RSPB and the University of East Anglia has been trying to work out if it is possible to substantially improve Lapwing productivity without using intensive, costly predator management, in the form of permanent electric fences.

Background

graphThe RSPB has been monitoring breeding waders on their Berney Marshes reserve in Norfolk for over 20 years. Even with fox control, a wader-friendly grazing regime and sensitive regulation of water levels, Lapwing nesting success on this site is still below 0.6-0.8 chicks per pairs in most years, which is the estimated range required for population stability (Macdonald & Bolton 2008a). Predation is the main issue that is still limiting productivity.

Previous work has shown that:

  • Providing areas of tall, dense grass (often along field verges) can encourage populations of small mammals, which are the main prey of most wader nest predators (Laidlaw et al 2012).
  • The lay-out of wet features can influence Lapwing nesting densities (Eglington et al 2008).
  • Nest survival is higher when Lapwing densities are higher (Macdonald & Bolton 2008b).

The team believe that these three factors – small mammal distribution, surface water and Lapwing nesting density – are very likely to influence the behaviour and distribution of red foxes, the key predator in this study area.

There is more background information in the WaderTales blog entitled A Helping Hand for Lapwings and in a perspectives article in Wader Study by Jen Smart.

ditchIn a recent RSPB/UEA project, Dr Becky Laidlaw has investigated these relationships further and has then used the trends that have been established to model different potential management scenarios. What could happen if nesting densities, wetness and the proximity of verges with small mammals could all be varied in the best ways possible? Is there a theoretical scenario in which productivity is high enough to fuel population growth?

The paper is published as: Scenarios of habitat management options to reduce predator impacts on nesting waders. Rebecca A. Laidlaw, Jennifer Smart, Mark A. Smart and Jennifer A. Gill 2016 Journal of Applied Ecology doi: 10.1111/1365-2664.12838

The right habitat mix?

Using relationships established from previous studies and collating seven years of information on over 1400 individual nesting attempts, Dr Becky Laidlaw and her colleagues from UEA and RSPB saw that, not only was nesting success being influenced by wetness and the proximity of tall grass, there were some subtleties relating to the way that habitats are distributed. Might it be possible to  redesign the site so as to create a patchwork that could achieve the required productivity levels? Becky had two variables to play with – verges and wet features.

Verges influence predation rates, with Lapwing nests further from tall vegetation areas having a higher likelihood of being predated. This makes sense if foxes are concentrating on catching small mammals in areas with high mammal densities, and are more likely to ignore eggs that are laid in short grass close to mammal-rich verges.

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There are plenty of wet features at Berney. The River Yare is in the foreground.

Water also influences wader nest predation rates. This is not surprising; if you are a fox, it is probably going to be harder to search for nests in a wet field with lots of pools and ditches than in a dry field. Interestingly, the study found that nests in the centre of dry fields were more at risk than those at the centre of wet fields. In a wet field, it’s riskier to nest along the edge, whilst in a dry field the risk increases the further the nest is from the edge.

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Part of a figure in Scenarios of habitat management options to reduce predator impacts, published in Journal of Applied Ecology by Laidlaw et al (Journal of Applied Ecology, 2016)

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The team want to see more Lapwing chicks. These are newly-hatched.

The study confirmed that isolated Lapwing nests are more at risk of predation, potentially because single pairs don’t benefit from the mobbing defensive behaviour provided by having plenty of nesting neighbours. They found a similar pattern with Redshank nest predation risk; these scarcer breeding waders appear to be protected by the presence of more Lapwing.

Scenario modelling

Becky then worked with Mark Smart, the RSPB manager with responsibility for Berney Marshes, to model some potential future management scenarios for the site. They worked out where it would be feasible to add or remove verges and increase or decrease surface wetness within fields. Becky then used existing relationships to predict what changes in nest predation rates might be expected. Were there management options that could significantly increase survival rates of nests?

ralphBecky compared the different modelled management scenarios with the long term average nest predation rate for the site. She found a significant (roughly 20%) reduction in nest predation could potentially be achieved with the addition of tall vegetation, but only for nests close to field edges in areas of high Lapwing nest density. Importantly, this sort of decrease in nest predation levels could potentially increase the number of chicks hatching by around 100 each year, but such management relies upon areas of sufficiently high Lapwing breeding density being available.

The influence of nesting density

The aim of this applied research was to find a way to manage breeding habitat for Lapwing that could be rolled out to areas of conservation-sensitive farming outside nature reserves. Given the subtleties of creating the right patchwork of wet features and long grass at Berney, it’s going to be tricky to get similar benefits on other sites. If habitat management alone is not enough, even when used alongside fox control, then what else can be done?

Becky has a possible answer. “The breeding density measure we are using is the number of active nests within 100 metres of a nest. It may therefore be important not only for nests to be clustered in fields with appropriate conditions, but also that they are at the same stage at the same time. Synchronous nesting is something that we think might be very important.”

fenceFrom data collected on RSPB reserves with and without electric fences (which exclude foxes), it is clear that fencing greatly increases the synchrony of nesting attempts (because most of the early nesting attempts are successful). Given that the density of active nests has a major effect on nest survival rates, increasing the number of nests active at the same time may well provide a greater level of protection, through the mobbing behaviour of Lapwing, and therefore lead to greater hatching success.

As part of a new piece of research (funded by NERC, a UK government research council), Becky and the UEA/RSPB team are going to test whether the provision of temporary electric fences for just the early part of the breeding season can provide sufficient protection to increase hatching success, as a consequence of nests being more synchronous. If early-reared chicks are more likely to fledge than late-reared chicks, there also may be additional knock-on benefits post-hatching and through to the recruitment stage.

Becky is hopeful. “We understand how wader predation rates are influenced by the proximity to verges, the accessibility issues caused by water and the mobbing, defensive behaviour of waders. We are now interested in determining the best way to use this information in management. With the new work with fences we’re going to be specifically exploring the importance of synchrony to both nest success and productivity”.

Scenarios of habitat management options to reduce predator impacts on nesting waders. Rebecca A. Laidlaw, Jennifer Smart, Mark A. Smart and Jennifer A. Gill 2016 Journal of Applied Ecology doi: 10.1111/1365-2664.12838

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