Seasonal change in peregrine abundance. Seasonal index of peregrine abundance, based on the mean number of sightings during standardized daily surveys, grouped into successive 5-day periods, 1986 - 2000. The annual peak is reached during October, and declines during the course of the winter. A second peak follows in mid-April. Pacific dunlins' winter residence on the Fraser estuary begins just after the autumn peak, and ends just before the spring peak of the peregrine index. The data were collected by John Ireland, manager of the George C. Reifel Migratory Bird Sanctuary, located on the Fraser estuary. Based on Lank et al. .
Ydenberg et al. BMC Ecology 2010 10:1 doi:10.1186/1472-6785-10-1