The research shows that, in addition to maintaining healthy numbers of curlew, grouse moor management can provide a surplus of fledglings, potentially aiding species recovery.
Curlew reared 1.05 fledglings per pair on grouse moors, almost double the rate of 0.5-0.6 needed to keep numbers stable. In contrast, on nearby non-grouse moors they only fledged 0.27 chicks per pair, well below that break-even point.
This is against a backdrop of the UK curlew population’s steady decline since the 1990s. Around a quarter of the world’s curlew breed here. However, since 1990 that population has halved, significantly impacting global numbers. The species has IUCN Near Threatened status and is red-listed in the UK.
Researchers also found that other wading birds, such as lapwings, golden plovers, oystercatchers and redshanks, benefited and raised more chicks on sites where predator control was in place as part of grouse management.
Director of Upland Research Dr Dave Baines, who led the project, said: “This study shows that the provision of suitable habitat alone is insufficient to prevent the decline of the curlew, which is threatened with extinction in many parts of the UK.
“By providing adequate control of generalist avian and mammalian predators alongside suitable habitat, grouse moor management not only maintains stable numbers of curlew and other waders, but also increases their productivity to the point of generating a surplus.
“In contrast, the control sites used in the comparative study, which had similar habitat but lacked predation management, saw continued declines.”
The team of scientists found that twice as many waders, on average four species, were recorded on grouse moors, compared to non-grouse moors, where on average three species were seen. Redshank and golden plover were found on half of the grouse moors studied, but only on 20% of non-grouse moors.
On grouse moors, it was estimated that two thirds of curlew pairs successfully hatched chicks, compared to just 17% of pairs on non-grouse moors.
They also found that, whilst habitat measures varied between sites in different regions, they showed no significant differences between grouse moors and non-grouse moors in the same block.
The study suggests that without predator control on UK grouse moors, and specifically the control of foxes and corvids, national curlew declines would have been more severe. In addition to loss of habitat and changes in farming methods, reduced breeding success due to egg and chick predation is a limiting factor on curlew recovery.