Dependence of spatial scale in landscape associations with cause‐specific predation of snowy plover nests

Hedgerows interact with forests to shape the abundance of mesopredators and their predation rate on eggs in farmland landscapes

Nest predation is the main cause of reproductive failure, particularly in ground-nesting birds on farmlands. Understanding the links between nest predation and habitat change can help design effective management schemes to constrain the negative impact of predation pressure on birds. However, the mechanisms underlying the relationships between landscape attributes, predator distribution, and nest predation are still unclear. Here, we use an experimental approach to examine the effects of distance to the hedgerow as well as hedgerow and forest densities on the abundance of major mesopredators of ground nests of our study area (i.e., corvids) and on the predation rate of artificial ground nests (n = 2576). We found evidence that landscape configuration influenced predation patterns differently depending on the predator species. Nest predation by corvids was more likely in homogeneous and open agricultural landscapes with a low density of forest and hedgerows, whereas predation by other predators was more likely close to hedgerows. Nest predation by corvids and the abundance of corvids also tended to be lower in landscapes dominated by grasslands. Other variables such as road density and distance to human settlements had contrasted effects on the likelihood of a nest being depredated by corvids, i.e., no effect with proximity to human settlements and decreasing trend with road density. Altogether, our results suggest that landscape features interact with mesopredator distribution and their predation rates of ground nests. Therefore, from a conservation and management perspective, a heterogeneous agricultural landscape that includes a mixture of crops associated with patches of forests, hedgerows, and grasslands offering alternative food to generalist predators should contribute to reducing ground-nesting bird predation.

Good neighbors? Does aggregation of nests in an Arctic-breeding shorebird influence daily survival rates?

Our current understanding of the factors that influence where birds nest is incomplete, yet such information is important for accurate demographic assessments. To address questions related to spatial distributions of shorebird nests and to evaluate factors that may affect nest distribution in these species, during 2017 and 2019, we studied a small population of semipalmated sandpiper Calidris pusilla breeding in the Central Canadian Arctic, near the Karrak Lake Research Station, in Nunavut. The spatial distribution of semipalmated sandpiper nests at this site suggested loose aggregation, with median nearest neighbor distances of 73.8 m and 92.0 m in 2017 and 2019, respectively, while no nests were detected on mainland areas in the vicinity. Evidence for the influence of nesting distribution on the daily survival rate of nests, however, was mixed. Neither nearest neighbor distance nor local nest density had a significant effect on daily nest survival in 2017, but in 2019, the best approximating model included an effect of local nest density, which indicated that nests in areas of high density had reduced survival rates. Contrary to other studies assessing settlement and nest site selection in semipalmated sandpipers, the spatial distribution of nests in this population demonstrates aggregation in an otherwise territorial species, but suggests that aggregated nesting can impose a cost on nest survival under certain conditions.