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Feeding technique gives Scotland's ground-nesting birds 'breeding' room

A study focused on protecting Scotland's capercaillie population by managing predators through non-lethal means has seen brood numbers double in target areas.

The capercaillie is a ground-nesting bird that, with just over 500 left in the wild, is in danger of extinction in the U.K. One contributor to its decline is the eating of eggs and chicks by predators, including another protected species, the pine marten.

Diversionary feeding is a conservation technique designed to reduce predator impacts on vulnerable species without harming the predators themselves. By providing an alternative, easy meal—deer carrion in this study—it gives predators a readily accessible food source so they don't need to search for rarer food like capercaillie nests in the same area.

Conducted over three years in the Cairngorms, the research is the result of a partnership between the University of Aberdeen, the University of St Andrews, Forestry and Land Scotland, RSPB Scotland, NatureScot and Wildland Ltd working under the umbrella of the Cairngorms Connect Predator Project.

It used camera traps to monitor capercaillie broods in locations where diversionary feeding was in place. Researchers found that in areas where alternative food was available, 85% of capercaillie hens detected had chicks, compared to just 37% in unfed sites.

This resulted in an increase in the number of predicted chicks per hen, more than doubling, rising from 0.82 chicks per hen without feeding to 1.90 with feeding—an increase in capercaillie productivity by 130%.

The study confirmed that the boost in chicks per hen was directly linked to a higher chance that a hen had a brood at all, indicating that diversionary feeding reduces catastrophic brood failure often caused by nest predation.

These findings build on earlier results from an published in 2024 that found a nearly 83% increase in artificial nest survival from a 50% reduction in pine marten predation, with diversionary feeding.

The latest research shows the results translate to real-life breeding outcomes.

"This study provides compelling, robust, landscape-scale evidence that diversionary feeding can reduce the impact of recovering predators, without killing them, aligning with shifting ethical and ecological goals for conservation management in the UK," said Dr. Jack Bamber, lecturer in Ecology and Conservation at the University of Aberdeen's School of Biological Sciences, who led the research project.

"The combination of rigorous experimentation and innovative monitoring indicates that this method is worth exploration for other species vulnerable to predation, with land managers concerned with other rare prey, and land managers aiming to help capercaillie elsewhere in Europe already considering this tool as an option for them to trial and apply in future."

The new research, which has been in the journal Proceedings of the Royal Society B, also outlines how deer carrion was offered only during a focused eight week window when capercaillie were nesting and chicks hatching, ensuring it reduced nest predation at the most critical time.

"This short-term feeding period is carefully selected to reduce the chance of increasing predator populations. Using waste products from ongoing deer culling makes it a sustainable and ethical approach for protecting endangered species," added Jack.

Diversionary feeding is now a key element of the with 15 sites already deploying the tool as part of the plan. This is set to increase with the aim for diversionary feeding to be delivered on all sites with recent hen records in the Cairngorms National Park by 2026.

Dr. Chris Sutherland from the Center for Research into Ecology and Environmental Modeling at the University of St Andrews said, "This project is an excellent example of how the impact of research can be maximized when it is co-designed in close collaboration with the wildlife managers and policy makers. Doing so enabled us to deliver timely, decision-ready evidence underpinned by scientific and statistical rigor."

Colin Leslie, Forestry Land Scotland Environment Advisor, said, "Over the past 20 years, we have implemented a range of conservation measures to try to boost capercaillie numbers, including fence removal, habitat improvements and, more recently, diversionary feeding to reduce predator impacts on breeding capercaillie. Diversionary feeding enables FLS to continue to avoid using legal forms of predator control, which have not proven to be effective in the past.

"This combination of techniques has seen an increase in capercaillie breeding success even as the number and diversity of predators was increasing and balancing itself out to the levels that the habitat can naturally sustain. This research will very helpfully inform and shape conservation action for years to come and we are pleased to see it being adopted widely by managers of other capercaillie forests."

Kenny Kortland, lead for the Cairngorms Connect Predator Project, said, "This exemplary research has yielded a management technique that changes the foraging behavior of pine martens and doubles the breeding success of the rapidly declining capercaillie—it has the potential to reverse the fortunes of this amazing bird."

Carolyn Robertson, Cairngorms Nature Manager at the Cairngorms National Park Authority, said, "These findings are very encouraging for the Capercaillie Emergency Plan, which aims to improve capercaillie survival across the Cairngorms National Park, the last stronghold for the species in the UK. We look forward to supporting more land managers in capercaillie areas to deploy this technique to reduce the impact of predation during the breeding season."

Richard Mason, site manager at RSPB Scotland Abernethy, said, "Capercaillie are still struggling in Scotland, but there is renewed hope thanks to innovative research and delivery projects like diversionary feeding.

"At RSPB Scotland Abernethy we have embedded diversionary feeding in our annual work program and alongside other large-scale projects such as cattle grazing, heather cutting, bog woodland restoration and reducing human disturbance, we have seen the capercaillie population at Abernethy slowly increase for the last five years. It is exciting that many land holdings are deploying diversionary feeding, and we hope that together we can save this special species in Scotland."