02/05/2022
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Wintering curlew numbers falling across UK

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The UK's wintering population of Eurasian Curlew is in decline across the UK, according to British Trust for Ornithology (BTO) data.

Proposed as the most urgent conservation priority in the UK as a result of a decline in its breeding population, it is estimated that 58,000 pairs of Eurasian Curlew breed across the UK.

During the winter months numbers increase slightly to around 120,000 individuals, with most wintering birds favouring estuarine habitats. While wintering numbers increased during the 1980s and 1990s, they have been in decline since then.


As well as its breeding population being in freefall, research shows that Eurasian Curlew is also declining as a wintering bird (Chris Hawes).

To understand what might be driving these changes, scientists at the BTO have looked at the role of both local and more widespread factors. If local factors (such as disturbance from recreation uses, localised pollution events and new developments) influence what is happening at individual sites, then it should be possible to identify those sites at which these local factors are an issue and to then direct conservation action towards them. However, if the changing numbers are instead influenced by factors (such as climate change, sea level rise and national policy changes) that have an impact across many sites, action may be needed across a much broader geographical scale.

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It is also necessary to understand to what extent factors operating during the winter months influence the wider fortunes of UK curlew populations. If, for example, such factors only exert limited impact on curlew survival rates, and hence both wintering and breeding numbers, then the focus of conservation action for curlew populations should target the breeding grounds.

The research, published in Bird Study, found that the increase in wintering Eurasian Curlew numbers in the UK during the 1980s and early 1990s likely reflects a positive response to the cessation of hunting, together with a wider redistribution associated with milder winters across the European wintering range, both of which are broad-scale factors. Winter temperatures influenced annual abundance changes at the site level rather than having direct impacts on survival, so factors operating during the breeding season are likely to be the main drivers of the current population decline in this priority species and this should be where conservation efforts are focussed.
 
Ian Woodward, Research Ecologist at the BTO and lead author of the paper, said: "While we would expect to see an increase in curlew numbers, or at least stability, as a result of milder winters, numbers are falling due to the decline in the breeding populations and factors operating during the summer months. Although conservation action therefore needs to be targeted at the breeding population, protection of wintering sites will still be important, ensuring the curlew does not face added pressures during winter months."

 

Reference

Woodward, I D, Austin, G E, Boersch-Supan, P H, Thaxter, C B & Burton, N H K. 2022. Assessing drivers of winter abundance change in Eurasian Curlews Numenius arquata in England and Wales. Bird Study. DOI: https://doi.org/10.1080/00063657.2022.2049205