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Research news: assessing Curlew recovery, annual survival, and the Dutch/German perspective

Russ writes:

In recent weeks a series of important papers about Curlews and their conservation have been published, so here we provide an accessible summary of the key findings.


1) In a landmark paper in British Birds in 2015, the Eurasian Curlew was described as the UK’s highest conservation-priority bird species. Six years on, a new British Birds paper by David Douglas of RSPB, and colleagues (including several members of the CRP Steering Group), provides an assessment of conservation action in the intervening period.


Douglas, D.J.T. et al. (2021) Recovering the Eurasian Curlew in the UK and Ireland: progress since 2015 and looking ahead. British Birds, v.114, p.341-350.


The paper opens with a summary of various recent assessments of the Curlew breeding population in the UK and Ireland. The last UK-wide estimate was for 58,500 pairs in 2016, but of particular concern is the perilous state of the remaining population in the Republic of Ireland, Northern Ireland, Wales, and lowland southern England, which is now estimated to be in the range of just 2000-2500 pairs (albeit with high uncertainty). Alarmingly, there is now a significant extinction risk across much of this area within a decade or two, which represents roughly half of the UK and Ireland range. As stated by the authors, “away from northern England and Scotland the outlook is bleak”. The primary issue is poor productivity, with recent estimates of chicks fledged annually by each pair being as low as 0.1-0.3 in lowland England and Wales, well below the threshold of 0.4-0.6 chicks per pair that is required to maintain the population.


Although there is increased public and political awareness in the plight of the Curlew, policy actions that will help to deliver Curlew recovery are limited. For example, there are no UK Special Protection Areas (SPAs) for breeding Curlews, despite this being recommended in 2016, and existing Agri-Environment Schemes (AES) appear to have had limited impact, particularly in lowland areas; however, the new Environmental Land Management (ELM) scheme in England is identified as a vital policy mechanism going forwards.


More promising is the bottom-up effort across the UK which has seen over 50 Curlew conservation projects established in recent years, many involving novel partnerships between land managers, conservationists, policymakers, and local communities. The Curlew Recovery Partnership was established to help knit together these projects, and to provide a focal point for engagement with policymakers at a national level; similar initiatives have been developed in Scotland, Wales, and Ireland.


The fate of Curlews is strongly tied to land use in upland regions, and current and future threats such as afforestation, windfarms and legislation affecting grouse moor management are all mentioned. However, predation and agricultural intensification are identified as the key issues requiring underpinning research and appropriate policy tools; the latter are particularly challenging to deliver, given that any population-level recovery is likely to be on a timescale of a decade or more.


The authors conclude with the following priority actions for Curlews in the UK and Ireland:


  • A presumption against new forestry within important Curlew breeding areas

  • Integrated land-use policies that prevent perverse outcomes

  • Refinement of AES to support evidence-based prescriptions known to benefit Curlews, with a test of whether predator control as a farmland conservation tool can improve breeding success.

  • Introduction of collaborative AES supporting landscape-scale delivery across multiple land holdings

  • Monitoring of the effectiveness of AES for Curlews, with prescriptions modified where required

  • The establishment of a network of European protected sites for breeding Curlews including SPAs

  • Carry out research into how to reduce mesopredator densities in the countryside

  • Prevention of further drainage of Curlew breeding areas and reversal of historical drainage

  • Establish locally led and nationally coordinated networks of Curlew action groups in key areas, working alongside land managers to deliver Curlew-friendly management

  • Acquire a comprehensive understanding of regional and national Curlew abundance, trends, and distribution

  • Further trialling of head-starting, delivered alongside habitat restoration and other management

  • Improved community engagement in Curlew conservation issues


Despite the challenges outlined in the paper, the authors conclude that “We are only at the beginning of Curlew recovery in the UK and Ireland. One thing that the Curlew does have on its side is the weight of public affection and a desire to secure its future. If we all work together, we might just have a chance of doing so.”


2) As mentioned above, recent research has confirmed that poor breeding success is the primary driver of Curlew declines in the UK; this is supported by data on adult survival, which for Curlews is high and ensures they are often long-lived birds (typically 10-15 years, with a maximum recorded age of 32!). A new paper by Aonghais Cook of BTO, and colleagues, provides further confidence in annual survival rates by analysing ringing data collected over the last 50 years.


Cook, A.S.C.P et al. (2021) Temperature and density influence survival in a rapidly declining migratory shorebird. Biological Conservation, v.260, 109198.


Survival rates were first calculated based upon analysis of over 15,000 Curlews ringed in the breeding season in the UK, most of which were chicks. Of these, nearly 300 were recovered dead and 175 recaptured. Modelled results indicate adult survival rates of 89.8% and first-year survival rates of 32.6% over the last 50 years, with an encouraging increase after 1996 to 92.2% and 39.0%, respectively; these results show that if Curlews survive their relatively perilous first year of life, they tend to have very high survival. A smaller number of birds ringed in winter (4400 ringed, of which 730 were recaptured and 105 recovered dead) produced similar survival rates. A cessation of hunting pressure and a lower wintering population were thought to have increased survival rates in some areas, with lower survival noted in colder winters.


The authors also used the collected data to run a population growth model, showing that, at a national level, breeding success (calculated as chicks per pair per year) is around 0.25, whereas it needs to be at around 0.43 for population stability. These results enable conservationists to focus on increasing breeding success to secure Curlew recovery, but the authors also note that maintenance of high adult survival rates will be required, through protection of key wintering sites.


A useful summary of the paper can be viewed on the excellent WaderTales blog by Graham Appleton at the link below. Perhaps the most striking comment in Graham’s blog is that breeding Curlews in the UK need to produce an extra 10,000 chicks per year to achieve population stability, which really highlights the scale of the task ahead!

https://wadertales.wordpress.com/2021/06/12/more-curlew-chicks-needed/


3) Finally, a special issue of the Dutch/German journal Limosa, dedicated to Curlews, was published recently, and contains useful summaries of each article in English:

http://www.nou.nu/limosa/limosa_issue.php?volume=94&issue=1


The Dutch population of Curlews has halved in the last three decades (similar to the UK), with the last nationwide survey estimating 3800-4800 breeding pairs. In common with many northwest European countries, low productivity due to agricultural intensification and predation is thought to be the key driver of observed declines; adult survival is high and very similar to that reported by Cook et al. above.


Our Steering Group member, Samantha Franks of BTO, provided this useful synthesis of the special issue:


  • In recent decades, Curlew have shifted from breeding mainly on nature reserves to breeding on agricultural land - and of these, one third are on arable, with the remainder in grassland.

  • Breeding Curlew have disappeared from many 'natural' habitats (dunes, peatland, heathland, etc).

  • Previously, causes of nest failure were mainly due to agricultural activities; now, mainly predation (Fox and Carrion Crow the main egg predators identified using nest cameras)

  • Most chicks hatch after mowing, with parents moving them out onto mown habitats; it is thought that Buzzards are likely the main chick predator based on mobbing behaviour of adults.

  • 80% of resighted chicks returned to the study area to breed, with an average dispersal distance of 3.8 km.

  • Nest fencing can more than double the number of hatched chicks produced.

  • 60% of radio-tagged chicks died within a week.

  • Curlew families in arable quickly moved to extensive pasture.

  • Numbers of overwintering Curlew in the Netherlands have increased in most areas


Sam commented that this last finding is of particular interest when viewed alongside the decrease in UK wintering numbers - could it be due to a) Curlew increasingly short-stopping in the Wadden Sea and elsewhere in the Netherlands, as other species are; and/or b) juvenile settlement patterns? The wintering decrease in the UK has previously mainly been attributed to overall decreases in many European breeding populations, which overwinter in the UK).

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