Nesting success of yearling and older breeders in the Semipalmated Sandpiper, Calidris pusilla

Approximately 100 pairs of Semipalmated Sandpipers (Calidris pusilla) nested in a 2-km2 area at La Pérouse Bay, Manitoba, each year from 1980 to 1982. The proportion of nesting yearlings in the population varied from 3 to 10% in different years. Some aspects of the breeding biology of pairs containing at least one yearling were compared with those without yearlings. In 1980, a significantly lower proportion of nests of yearlings were successful (hatched at least one chick) compared with older pairs. In 1981 and 1982 no difference was observed. Nest failure was primarily caused by egg predation. No differences in clutch size or nest distribution were found between the two age groups, but eggs were significantly smaller in nests of yearling females and mean hatch date at yearling nests was later.