Breeding Cycle and Behavior of the Semipalmated Sandpiper at Barrow, Alaska

Abstract

Abstract Pair formation of Calidris pusilla near Barrow, Alaska occurs 3-6 days after the territory is established. The pair is then engaged in nest scraping displays during 2-3 days, in which 10-12 scrapes are made by the male and examined by the female. Eventually 2-3 scrapes are lined by the female, and in one of these the first egg is laid 4-6 days after pairing. During the egg-laying period further lining is performed by the female and partial incubation takes place by both sexes. Continuous incubation commences 8 h prior to laying of the 4th egg. Male and female alternate in incubation: in the first 2 days a turn lasts 3-5 h, and the duration gradually increases up to 13-14 h during the 2nd week. Long incubation turns reduce the number of approaches to the nest and may therefore reduce the chances of it being discovered by predators. The incubating bird is intermittently engaged in egg-rolling and in camouflaging the nest by bending adjacent grass blades over its back, and is constantly alert. The off-duty bird may feed 2-3 km away from the nest. The eggs hatch after 20 days of incubation, all within 1 day. Females desert the family 2-8 days after hatching: they desert late if hatching is early, and early if hatching is late in the season. After female departure the family moves from the nesting territory, typically in a high-centered polygonal area, to establish a home range as far as 2-3 km away, often in a low-centered polygonal area. During the first 6-8 days after hatching, the male prepares each evening a scrape for night brooding. After fledging, the male and young join wandering flocks.