Aggregation of nests in an Arctic-breeding shorebird and 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 neighbour distances of 73.8 m and 92.0 m in 2017 and 2019, respectively. Evidence for an influence of nesting distribution on daily survival rate of nests, however, was mixed. Neither nearest neighbour 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 a role for social attraction in an otherwise territorial species and suggests that aggregated nesting can impose a cost on nest survival under certain conditions.