Blog by Dr David Douglas, Principal Conservation Scientist; Dr Irena Tomankova, Conservation Scientist, and Sarah Sanders
The plight of the Eurasian curlew is a major conservation priority. Based on the combination of global conservation status (IUCN Near-Threatened), the global importance of the UK breeding population (19-27%) and the rapid decline of the UK breeding population (-48% since 1995), RSPB and others have argued that the curlew should be considered the UK’s highest conservation priority bird species.
Curlew on RSPB reserve Geltsdale (c) Andy Hay (rspb-images.com)
To recover curlew, we must turn the national population trend from a declining one to an increasing one. If that sounds daunting, let’s break it down in stages; first slow the rate of decline, then stabilise numbers, then begin increasing numbers.
What role is science playing in recovering curlew? There are various elements to the species recovery ‘journey’ that we use at RSPB;
The first two are those where science has the biggest role to play and are currently most relevant to curlew.
The essential diagnostic research has been done and we have a good understanding of the causes of curlew declines. In the absence of hunting and suction-dredging of their food, between-year survival is good and doesn’t appear to be driving curlew declines. In the breeding season it’s a different story; in the UK, and elsewhere, curlew frequently don’t raise enough young to maintain their numbers.
What are the causes of curlew decline?
Firstly, there is likely to have been a long-term deterioration in the extent and quality of curlew breeding habitat. Curlew prefer unimproved, damp grassland and moorland, lots of which has been replaced by intensive grassland, arable farming and forestry. The effects of this habitat loss on curlew across the UK are hard to quantify but are likely to have been substantial over recent decades, for example the estimated loss to forestry of habitat supporting 5000 breeding pairs in southern Scotland.
Secondly, high nest and chick predation rates are a key driver of declines. Predation is a natural event but the effects on birds are exacerbated in poorer quality habitats and by the high predator densities found in the UK, tipping the balance in favour of predators such as foxes and crows.
The science therefore tells us that curlew recovery requires sufficient suitable breeding habitat and predation levels that are low enough for successful breeding.
Curlew (c) Tom Marshall (rspb-images.com)
Finding a solution
This brings us to the solution testing phase. We are undertaking a curlew Trial Management Project (TMP); a large-scale scientific study testing whether habitat management and predator control is effective in improving curlew nesting success and breeding abundance. The TMP was entering its final year when COVID19 intervened and we suspended the management and monitoring. Whether we manage to complete the final year remains to be seen, but we’ve learned a lot so far.
Data analysis is still to be done, so we can’t yet report on the results, but interesting patterns are emerging.
Firstly, the area of habitat that needs to be managed for curlew is large. Curlew use large areas for raising their young and breed at relatively low densities compared to some other waders. This management also takes time to deliver over large areas, and curlew need time to respond to it, so curlew recovery will be a long-term process and must be delivered at a large scale.
Secondly, managing predation has brought into sharp focus the issue of why such management is required in the first place. The UK has the highest density of crows, and second highest density of foxes, in Europe. Curlew and other ground-nesting birds are attempting to cling on in landscapes that support high predator densities. Whilst direct management of predators, for example through lethal control, is humans’ way of attempting to reduce predation, it is merely stemming the flow of predators rather than addressing the underlying causes.
So whilst acknowledging what may be required for curlew in the short to medium term, we are already turning our attention to understanding the drivers of high predation pressure in the UK and how to reduce this. Evidence exists for some drivers, for example the role of forestry in supporting predators which then have impacts on adjacent open ground where curlew breed; and the release of tens of millions of non-native gamebirds which is associated with higher predator abundances. Addressing the drivers of high predation pressure is an increasing focus of our attention. If we don’t address it, we will struggle to recover curlew in the UK.
In summary, science has pointed clearly to the drivers of curlew declines and enabled us to design and trial solutions. The findings from the trial will hopefully enable us to advocate for wider roll-out of curlew-friendly solutions. The future of agri-environment support post-Brexit provides an opportunity to rethink UK land use so that the natural world is healthier and more resilient.
We thank Natural England and Scottish Natural Heritage for supporting the curlew Trial Management Project through the Action for Birds in England (AfBiE) partnership and Scotland Biodiversity Challenge Fund.
About the authors
Dr David Douglas works at the RSPB Centre for Conservation Science and leads RSPB’s UK upland research programme. This includes work to inform the recovery of declining species and also addresses wider land use issues including forestry, grazing, moorland burning and onshore wind farms, examining the impacts of these on upland species, habitats and the wider environment.
Dr Irena Tomankova works as a Conservation scientist at the RSPB Centre for Conservation Science, leading the delivery of science within the Curlew Trial Management Project.
Sarah Sanders manages the curlew recovery programme at the RSPB, which involves co-ordinating and supporting colleagues from across the organisation to improve the conservation prospects for this species.
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