Pacific Dunlin Calidris alpina pacifica show a high propensity for second clutch production

Abstract

The Predation Danger Hypothesis suggests that shorebirds adjust aspects of their annual schedules to limit the amount of time they are exposed to the danger posed by the presence of Peregrine Falcons (Falco peregrinus) and other raptors. For example, Pacific Dunlin (Calidris alpina pacifica) remain near their breeding grounds on the Yukon-Kuskokwim Delta, Alaska to molt, and migrate southward after peak Peregrine Falcon migration has passed. This extended residence in the north may enable them to increase the time they devote to reproductive activities and enhancing their reproductive output, either by increasing the length of bi-parental brood care or by producing more clutches. In this paper, I describe the breeding ecology of Pacific Dunlin and relate my results to their migration strategy. Pacific Dunlin females deserted their broods, on average, at 5 days of age, leaving the remainder of the 19-day brood care period to their mates. This resembles the parental care patterns of other Calidris species. However, Pacific Dunlin exhibited a high propensity for replacing first clutches that failed (75%), and 17% of individuals who successfully hatched their first nest deserted their broods and went on to produce a clutch with a new mate (i.e., double brood). These rates are high compared to other subspecies of Dunlin suggesting that Pacific Dunlin take advantage of their extended time on the breeding grounds to increase their reproductive output.