Curlews can’t wait for a treatment plan

Europe is losing 5000 Curlews every year. What can we all do to stop – or even slow down the decline?

RC single bird muddy edgeIf a patient presents with a problem, it’s the job of the health professional to work out the root cause, to come up with a treatment plan and to check that it works. That’s the process that is used for bird conservation – notice, diagnose, treat and monitor. Sometimes, however, the patient is in such a serious condition that you cannot wait for a full set of test results, you just have to try something. That’s the situation with Curlew in the United Kingdom; the losses are so rapid that people are already taking local action to try to increase chick numbers (see some links at the bottom).

This blog focuses on a new paper, by Samantha Franks and colleagues from the BTO and RSPB, that tries to identify the primary factors associated with the species’ decline at a national scale. Unsurprisingly, the answers point to changes in ‘habitat’ and ‘predation’ but it’s worth looking at the detail.

Background

The United Kingdom is one of the key breeding areas for Eurasian Curlew, accounting for an estimated 19-27% of the global population. Within the UK, breeding Curlew numbers have dropped by 48% in the last 20 years – earning the species the dubious distinction of red-listed status in 2015. We are responsible for a staggering estimated loss of 13.5% of the European population during this period.

categoriesThere’s more about the national and international problems for Curlew in this blog (Is the Curlew really near-threatened?). Sadly, the Eurasian Curlew is not alone – almost every member of the Numeniini (curlews, godwits and Upland Sandpiper) is in trouble, as you can read here (Why are we losing our large waders?).

Theories

The aim of the new study by BTO and RSPB scientists is to use national figures to assess whether there is evidence to support or refute previous theories about the causes of Curlew declines. The paper starts with a thorough and fully-referenced overview of existing evidence for potential causes of the population change. At its heart is a discussion as to how management affects Curlews, through things like changes to upland grazing patterns and land-use modifications which may have had unintentionally positive effects on generalist predators. Changes to weather patterns provide additional challenges. The suggested drivers of the declines that have been observed and in some cases measured are summarised here.

Potential positive effects on Curlews:

  • GT inbye

    Adding some improved grassland to the habitat matrix

    Increased fertility of improved grassland could boost invertebrate numbers and support Curlews

  • Gamebird management may provide better habitat conditions for breeding Curlew
  • Site protection might limit development and protect habitat

Potential negative effects on Curlews:

  • Intensification of agricultural activity – e.g. removal of rough, damp patches used by Curlew
  • Conversion of open habitat into woodland may reduce feeding opportunities and harbour predators
  • Increases in numbers of general predators
  • Climate change – warmer summer temperatures/reduced rainfall may change prey availability
  • Declining quality of heaths and bogs may reduce nesting opportunities

Data analysis

BBSThe paper uses data collected by thousands of volunteers who contribute to the Breeding Bird Survey (BBS), organised by the BTO in partnership with JNCC and RSPB. The team focused upon Curlew breeding distributions in Great Britain during the periods 1995-99 and 2007-11, separately. They then considered patterns of change between the two periods.

The following potential correlates of distribution and change were investigated:

  • Changes to habitat – as evidenced from land cover maps
  • Site protection – as included in the World Database of Protected Areas
  • Topography – altitude, slope and organic carbon content of soils
  • Climate – summer and winter rainfall and temperature data
  • Game management – assessed from maps of strip-burning in the uplands and BBS data on gamebird abundance
  • Predator populations – crow and fox data from BBS counts

GT chickSo, how well did the patterns of change fit with the theories as to which factors might be causing the collapse of Curlew numbers? Let’s start with a couple of the strange findings from the 1995-99 period. It illustrates just how hard it is to interpret correlative relationships. Just because A and B happen at the same time, does it mean that A is actually causing B?

1995-99 anomalies

When the research team investigated links between Curlew abundance in 1995-99 and the variables that might explain the species’ distribution, they found that Curlews were associated with semi-natural grassland, heathland and bog, as one might expect. However, Curlew were also more abundant in areas with a greater amount of woodland in the landscape, albeit this being a relatively weak relationship . Given previous research by David Douglas et al in the Journal of Applied Ecology had shown a negative effect of woodland on Curlew abundance, this seemed strange. This unexpected association with woodland was reversed when data for 2007-11 were considered and when the changes between the two periods were analysed. The authors’ explanation is that tree planting prior to the 1995-99 surveys may have taken place in some Curlew breeding areas, that the trees were still becoming established and that the Curlews still present.  Whether these birds were successfully raising chicks we shall never know.

RC burnt moorland

Moorland managed for Grouse shooting

Another anomaly in this first period was that Curlew density was highest in areas with high crow abundance. This may look odd until you also consider the strong association between Curlew numbers and numbers of Red Grouse and Pheasant. Provide the right conditions for these ground-nesting species to flourish and you’re likely to draw in predators.

The bigger picture

Fortunately, and thanks to the volunteers who collect Breeding Bird Survey data every year, the researchers were not constrained to one time period. They could also look at 2007-11 and changes in Curlew distribution in the intervening period. Anyone interested in the finer detail will want to read the whole paper but here are my take-home messages.

Habitat associations

  • GT nest in uncut juncus

    Nesting in rushes

    Semi-natural grassland supports the highest densities of breeding Curlew, of any habitat.

  • Enclosed farmland, particularly when fields contain arable crops, has far fewer Curlews, supporting the theory that the ‘improvement’ of semi-natural habitats is bad news for the species.
  • While ‘improved’ grassland was positively associated with curlew abundance in 1995–99, the more recent results suggest these habitats have declined in importance. Perhaps Curlews have withdrawn from these nutrient-rich, structure-less habitats as numbers have declined?
  • While upland heath and, to a lesser extent, bog habitats are important breeding habitats for British Curlew, they appear to have become less important through time. 

Game management and predation

  • GT predated

    Predated nest

    High Curlew densities were associated with areas with more Red Grouse and Pheasant, despite management for Red Grouse and Pheasant occurring in largely different habitats.

  • Curlew population declines were greatest in areas with high crow abundance and numbers of Curlews were lower in areas with more foxes. “Our findings support the hypothesis that measures to reduce predation pressure from generalist predators such as foxes and crows are likely to be very important for Curlew”.
  • While Red Grouse abundance was positively associated with Curlew abundance in both time periods, rotational strip burning was negatively associated with Curlew abundance in 2007–11, though weakly so. The authors suggest “while low levels of strip burning could plausibly be beneficial for Curlew, by creating variation in habitat structure, too much may be detrimental, as burning can impact peatland hydrology and consequently soil moisture, reduce invertebrate prey, or alter vegetation structure or composition”.
  • Significant areas of semi-natural habitats in Britain are protected as Sites of Special Scientific Interest, National Nature Reserves and/or Natura 2000 sites. Curlew densities are now higher where there is a greater extent of protected area coverage.

Climate change

  • Curlew abundance is lower if summer temperatures are higher.
  • Declines were greatest in areas of high winter temperature, conditions which may have negative impacts on invertebrate populations.
  • Declines were greatest in areas of low summer rainfall.

What to do for Curlews?

nest in short vegetation

Nowhere to hide – Curlew nesting in cut rush

We cannot do much about climate impacts in the short term, and site protection is unlikely to reverse the national declines. The key things to focus on, according to the authors of this new paper, are “habitat restoration and reducing the negative impacts of predators”. Even if the details of the treatment plan have not been worked out, there appears to be a general diagnosis – there is not enough habitat of sufficient quality for Curlews to raise their chicks. While predator impacts may not have been the original cause of population declines, there is a broad consensus that reducing predator pressure is essential for successful species recovery.

So, we’ve noticed a decline, there is a diagnosis of the problem and there is a broadly accepted treatment plan of creating better habitat and reducing predator pressures. The next phase is to monitor what works, which is where national collaboration comes in. Curlews are not only found on nature reserves; they are ‘out there’ in land owned and managed by all sorts of people with a broad range of motivations, including farmers, shooting estates, statutory agencies and conservation charities. Single land-owners and local groups are working in partnerships to try to improve breeding habitat and reduce predation. What is working – and in which circumstances?

GT ad and chickAt the end of the new paper is a key section advocating “the need for the rapid establishment of intensive studies to identify the mechanistic drivers of the patterns observed here and to test potential conservation management interventions”. Ideally, these will look at issues such as:

  • RC poolHow Curlew numbers relate to variations in how intensively land is used for agriculture, forestry and grouse moor management.
  • How predator abundance and invertebrate resources relate to Curlew abundance and importantly, reproductive success.
  • Which potential restorative conservation management interventions best improve habitat quality and reduce the impacts of generalist predators.
  • Whether there are agri-environment schemes that can improve habitat quality for Curlew more broadly in the wider countryside. This may well involve better understanding the impacts of drainage on soil invertebrates.

In the absence of sufficient funding to conduct all these experiments as proper trials, it is to be hoped that the RSPB’s Trial Management Project and a new initiative by the Game & Wildlife Conservation Trust (links below) will enable local experiences to be shared in a national framework. Further collaboration is being encouraged through the UK and Ireland Curlew Action Group and a series of workshops organised through The Curlew Forum.

Links to local and collaborative initiatives in the UK and Ireland

RSPB GWCThttps://ww2.rspb.org.uk/our-work/conservation/projects/curlew-recovery-programme

https://www.gwct.org.uk/action-for-curlew/

http://www.curlewcall.org/

https://www.npws.ie/research-projects/animal-species/birds/curlew-task-force-august-2017

This list will be updated as and when I am notified of appropriate links.

Paper

Environmental correlates of breeding abundance and population change of Eurasian curlew Numenius arquata in Britain

The paper appeared in Bird Study, published by BTO, on 31 August 2017.

The authors are Samantha E. Franks (BTO), David J. T. Douglas (RSPB), Simon Gillings (BTO) and James W. Pearce-Higgins (BTO). BTO work on this paper was funded via the Trust’s Curlew Appeal.

RC roosting


 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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A great summer for Iceland’s waders?

As July 2017 turned into August, the first juvenile Icelandic Black-tailed Godwits started to arrive in the UK – soon they were everywhere. Had this been a good year for waders and wader research in Iceland?

juvvy blackwits

Flock of juvenile Black-tailed Godwits in Devon

An increasing amount of wader research is taking place in Iceland, much of which is part of an international partnership between the South Iceland Research Centre (University of Iceland), the University of East Anglia (UK) and the University of Aveiro (Portugal). Although the main focus has been on Black-tailed Godwits, Whimbrels and Oystercatchers, there is a lot more to this collaboration.

Winter into spring

january surveyThe spring season started early for Verónica Méndez, who is studying the migratory decisions made by Iceland’s Oystercatchers. About one third of these birds stay in Iceland for the winter but most are thought to migrate to Ireland and western coasts of the UK. By looking for colour-ringed individuals in January she was pretty sure that she would be sampling resident birds. There’s a blog about this project here. At the same time, sightings of migratory birds were being reported from the UK and Ireland.

Since 2000, there have been annual spring surveys of arriving Black-tailed Godwits. Jenny Gill and I arrived on 13 April and started our survey routine of regular visits to estuaries, wetlands and stubble fields in south and west Iceland. Icelandic birdwatchers cover other sites in the east and south of Iceland. The dates of the arrivals of individual birds have already contributed to a paper about what is driving earlier spring migration of the species, which is written up in this blog.

FrenchIn cold northerlies, migration from Ireland, the UK and mainland Europe was slow in 2017. This is something we have seen before and described in this blog about the appearance of large flocks in Scotland. A record number of Black-tailed Godwits – 2270 birds in total – were seen on the Scottish island of Tiree on 25 April 2017, including a minimum of 23 colour-ringed birds. We saw one of these birds four days later, fast asleep on a hay field near the south coast of Iceland.

Breeding studies

The 2016/17 winter had been relatively warm and wet in Iceland and the ground was not frozen when waders returned from Europe. The Black-tailed Godwits did not stay for long on the estuaries before moving inland to breeding territories.

The Oystercatcher project got off to an early start. oyc crossIn collaboration with Sölvi R Vignisson, Ólafur Torfason and Guðmundur Örn Benediktsson, the team colour-ringed 177 new adults and 144 chicks in a range of sites around Iceland. This year’s adults have white rings with two letters on the left leg and two colour-rings on the right, whilst chicks have grey instead of white. A smaller number of youngsters ringed in 2016 have green rings with engraved letters and some adults from previous years have green flags.

As part of a study to try to understand the migratory behaviour of young Oystercatchers, José Alves & Verónica Méndez have fitted GPS/GSM transmitters to a small number of big chicks. Which birds will migrate and what determines the strategy? Two birds have already made what appear to be exploratory trips around southwest Iceland, before returning to their natal sites.

FIRST2OYCSAt the time of writing (26 August), none of the birds with trackers has yet left Iceland but the first two colour-ringed birds have been seen in Ireland – an adult from the east and a juvenile from the south (see map).

Breeding studies of Black-tailed Godwits have been ongoing since 2001 and a small number of adults and chicks were ringed this year. This graph, which appears in the blog Why is spring migration getting earlier? showed that recent recruits to the population arrive in Iceland earlier than birds from previous generations.

timing hatching

Dates of spring arrival into Iceland of 46 individuals hatched in different years and subsequently recorded on spring arrival (reproduced from Gill et al. 2014)

Pressures on Iceland’s waders

tableIceland is hugely important for breeding waders. It holds about 75% of Europe’s breeding Whimbrel, over half of the region’s Dunlin and perhaps half of its Golden Plover. Although changes to the way land is farmed may have provided opportunities for some species, such as Black-tailed Godwits, intensification and the timing of operations have the potential to impact distribution and breeding success. A paper by Lilja Jóhannesdóttir was written up as a blog Do Iceland’s farmers care about wader conservation? and she successfully completed her PhD Links between agricultural management and wader populations in sub-arctic landscapes in June 2017.

T with BTGThe amount of woodland is changing in Iceland, with more forestry and shelter belts around summer cottages. This is an issue that was highlighted in an AEWA report published in the autumn of 2016. In the spring, Aldís Pálsdóttir started a new PhD at the University of Iceland, in which she will explore the effects of forestry on breeding waders in Iceland. Her first task in the field was to measure the effects of forest patches on breeding wader distribution, which involved walking over 400km of survey transects! Complementary work this summer by Harry Ewing, as part of his Masters in Applied Ecology and Conservation at the University of East Anglia, has explored how levels of wader nest predation vary with distance from forest patches. There’s more about the effects of woodland on breeding waders in this recent Lapwing blog: Mastering Lapwing Conservation.

Deploying and collecting geolocators to study migration

Geolocators provide a cost-effective way of collecting information on the year-round movements of individual birds, as long as birds can be recaught in the breeding season following the deployment of the tags. This blog summarises a useful paper about the safe use of geolocators.

whimbrelCamilo Carneiro is studying for a PhD at the University of Aveiro. His project, entitled Bridging from arctic to the tropics: implications of long distance migration to individual fitness, takes him to Iceland in the summer and to Mauritania and Guinea-Bissau in the winter time. By putting geolocators on Whimbrels in Iceland, he can establish the migration strategies of individuals. He has already mapped 96 migrations of 32 individual birds and we look forward to seeing the results from his studies. A flavour can be found here, in blogs about the migration of Icelandic Whimbrel and the first results of initial geolocator work by José Alves, one of Camilo’s supervisors.

RingoRinged Plovers that breed in Iceland are thought to spend the winter in southern Europe and northern Africa. Böðvar Þórisson has been studying breeding Ringed Plovers for many years, with recent work including using geolocators to explore the migration routes and timings of individuals. This year he managed to retrieve 7 of the 9 geolocators that he put on in 2016 – look out for a poster on this at IWSG 2017 in Prague. These birds had spent their winters in Mauritania, Portugal, Spain, France and southern England. 16 new tags were deployed during 2017, including a number on the same birds as in 2016.

RNPIn collaboration with Yann Kolbeinsson and Rob van Bemmelen, Jóse Alves and other members of the team have been using geolocators to study Red-necked Phalarope migration. Some birds migrate to the Pacific Ocean around coastal South America and the Galapagos but how do they get there and what is the timing of their movements? These two articles tell the story of one bird from Shetland (UK) and moulting flocks in the Bay of Fundy (Canada). Sixteen new geolocators were deployed but none of the ten deployed in 2016 were retrieved. Perhaps Red-necked Phalaropes are not that site-faithful?

So how good a breeding season was it?

2017 chick surveyAs described in this blog, the productivity of Iceland’s Black-tailed Godwits is closely linked to May temperatures – unless a volcano erupts. Each June, Tómas Gunnarsson collects information on the number of successful broods, based on a 198 km car-based transect through south Iceland. Repeating this survey in 2017 he discovered a record number of broods, adding the right-hand orange dot to the graph alongside. May 2017 was warmer than any spring during the study period covered for the IBIS paper and the number of June broods was higher too. It is not surprising that there are so many reports of juvenile Icelandic Black-tailed Godwits in Britain and Ireland this August.

For other species, where productivity is recorded in the same manner (Whimbrels, Oystercatchers and Golden Plovers), the 2017 season was also the best in the period since 2012. Perhaps other species, such as Redshank and Snipe, did well too? Will these cohorts of juveniles be big enough for there to be a detectable uplift in number on this winter’s I-WeBS and  WeBS counts?

sunset


 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