Data from: Predator-mediated negative effects of overabundant snow geese on arctic-nesting shorebirds

Overabundant species can strongly impact ecosystem functioning through
trophic cascades. The strong increase in several arctic geese populations,
primarily due to changes in agricultural practices in temperate regions,
can have severe direct impacts on tundra ecosystems through vegetation
degradation. However, predator-mediated negative effects of goose
overabundance on other tundra species can also be significant but are
poorly understood. We tested the hypothesis that goose abundance
negatively affects arctic-nesting shorebirds by increasing nest predation
pressure. We used six years of data collected within and near a greater
snow goose colony (Chen caerulescens atlantica) to evaluate the effect of
geese on the spatial variation in (1) the occurrence of shorebird nest
predators, (2) the nest predation risk (with artificial shorebird nests),
and (3) the occurrence of nesting shorebirds. We found that the goose
colony had a strong influence on the spatial distribution of nest
predators and nesting shorebirds. Occurrence of predators decreased, while
occurrence of nesting shorebirds increased with distance from the centroid
of the colony. The strength of these effects was modulated by lemming
density, the preferred prey for predators. Shorebird nest predation risk
also decreased with distance from the colony. Overall, these results
indicate that goose abundance negatively affects arctic-nesting shorebirds
through shared predators. Therefore, we show that the current decline of
some arctic shorebird populations may be in part mediated by a negative
effect of an overabundant species.