Capercaillie brood numbers soar with humane predator strategy

A new study from the University of St Andrews reveals that non-lethal predator management has successfully doubled capercaillie brood numbers in targeted areas of Scotland

The capercaillie is a culturally significant ground-nesting bird that, with just over 500 left in the wild, is in danger of extinction in the UK. 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 – to predators, it gives them 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 and around the Cairngorms National Park, the research, which is published today in Proceedings of the Royal Society B, is the result of a partnership between the University of St Andrews, the University of Aberdeen, 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 artificial-nest study 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.

Dr Chris Sutherland from the Centre for Research into Ecology and Environmental Modelling at the University of St Andrews said:  “This project is an excellent example of how the impact of research can be maximised 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 rigour”.

Dr Jack Bamber, from the University of Aberdeen, said “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.,”

“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 also outlines how deer carrion was offered only during a focused ight-week window when capercaillie were nesting and chicks hatching, ensuring it reduced nest predation at the most critical time.

Diversionary feeding is now endorsed in the Cairngorms Capercaillie Emergency Action Plan with 18 independent land holdings deploying diversionary feeding to help capercaillies in 2025.

The project was funded by the Scottish Universities Partnership for Environmental Research (SUPER) Doctoral Training Partnership.