Data from: Numerical response of mammalian carnivores to rodents affects bird reproduction in temperate forests: a case of apparent competition?

Resource pulses such as mast seeding in temperate forests may affect
interspecific interactions over multiple trophic levels and link different
seed and non-seed consumers directly via predation or indirectly via
shared predators. However, the nature and strength of interactions among
species remain unknown for most resource pulse driven ecosystems. We
considered five hypotheses concerning the influence of resource pulses on
the interactions between rodents, predators and bird reproduction with
data from northern Switzerland collected between 2010 and 2015. In
high-rodent-abundance-years, wood warbler (Phylloscopus sibilatrix) nest
survival was lower than in low-rodent-abundance-years, but rodents were
not important nest predators, in contrast to rodent-hunting predators. The
higher proportion of nests predated by rodent-hunting predators and their
increased occurrence in high-rodent-abundance-years suggests a
rodent-mediated aggregative numerical response of rodent-hunting
predators, which incidentally prey on the wood warbler’s ground nests.
There was no evidence that rodent-hunting predators responded
behaviourally by switching prey. Lastly, nest losses caused by
non-rodent-hunting predators were not related to rodent abundance. We show
that wood warblers and rodents are linked via shared predators in a manner
consistent with apparent competition, where an increase of one species
coincides with the decrease of another species mediated by shared
predators. Mast seeding frequency and annual seed production appear to
have increased over the past century, which may result in more frequent
high-rodent-abundance-years and generally higher peaking rodent
populations. The associated increase in the magnitude of apparent
competition may thus at least to some extent explain the wood warbler’s
decline in much of Western Europe.