Contemporary declines of shorebirds have been linked to environmental causes, but the role of predation in shorebird declines is not clear. From 1994 to 2015, we observed the interactions of Peregrine Falcons (Falco peregrinus) and Dunlin (Calidris alpina) wintering on the Pacific coast of British Columbia. Peregrine sightings per hour of observation declined on a seasonal basis from October to February, but increased chronologically from 0.36/hr in 1994 to 1.24/hr in 2015. Peregrines captured 205 Dunlin in 1369 attacks. Hunting success rates increased from 10.8% in October to 15.0% in the winter months. During high tide, when the intertidal zone was flooded, some Dunlin flocks spent up to 315 min in sustained flight over the ocean, apparently as an antipredator strategy, but other flocks roosted on the foreshore, or sat out the high-tide interval on agricultural fields inland. This study suggests that these anti-predator behaviors allow the Dunlin population to persist at Boundary Bay as predator numbers increase.
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Vol. 50 • No. 4