The influence of landscape factors on capercaillie nest predation rates
by two competing mesopredators: pine marten versus red fox
Abstract
Predation by pine martens (Martes martes) and red foxes (Vulpes vulpes)
is an important factor influencing the population dynamics of
capercaillie grouse (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 trap. We classified the fate of 156 nests and employed a
cause-specific hazard model to evaluate the competing risks of
capercaillie nest predation, 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.