Landscape factors influencing predation on capercaillie nests by two competing mesopredators: pine marten and red fox

Predation by pine martens (Martes martes) and red foxes (Vulpes vulpes) is
an important factor influencing the population dynamics of capercaillie
(Tetrao urogallus). However, there is a knowledge gap regarding the
relative effects of these mesopredators on the reproductive success of
capercaillie. To better understand how various landscape factors influence
nest predation by pine martens and red foxes, we monitored capercaillie
nests in Norway between 2009 and 2014 using camera traps. We classified
the fate of 156 nests and employed a cause-specific hazard model to
evaluate how different predators contributed to nest predation risk, while
accounting for landscape covariates such as distance from nest to
forest-clearcut edges, proximity to roads, and agricultural land density.
We found that predation by pine martens and red foxes was the predominant
hazard to capercaillie nests, with similar daily predation rates observed
for both mesopredators. Nest predation by pine martens decreased with
increasing agricultural land density and tended to increase along
gradients from clearcuts to forest interiors. Moreover, pine marten
predation tended to decrease with increasing distance from roads. Nest
predation by red foxes increased with distance from roads, but only in
areas characterized by high density of agricultural land. Red fox
predation was not associated with distance to forest-clearcut edges or to
agricultural land density. Our findings show that landscape factors
differentially influence pine marten and red fox predation on capercaillie
nests and highlight the importance of considering predator-specific
effects while managing populations of game birds and their predators.