Annually, large flocks of semipalmated sandpiper Calidris pusilla (Linnaeus, 1766) winter along South America coast, between September-April. They store fats in order to moult and return to their breeding grounds. Here, was examined body masses and plumage of adults Semipalmated Sandpipers during the departure month to evaluate the relationship between body mass and plumage. Fieldwork was conducted at Coroa do Avião (7º40'S, 34º50'W), Pernambuco. Birds were trapped in mist-nets between April 1990 and 1997. They were weighed, and aged according to plumage. Adult plumage may be (1) non-breeding, (2) pre-breeding, and (3) breeding. A total of 213 birds were weighed and examined, so that 8.0% (17) presented non-breeding plumage, 54.0% (115) pre-breeding, and 38.0% (81) breeding plumage. As in Semipalmated Sandpiper, 25g is the minimum body mass required to migrate, birds with breeding plumage and most with pre-breeding, were potentially apt to migrate. Non-breeding plumage birds presented smaller body mass. Apparently physiological problems and infestation may be important factors to explain over-summering, i.e., individuals remaining in the wintering grounds during the boreal summer.
Migration; over-summering; shorebirds; South America; wintering areas
