Sable Island, Nova Scotia, is the southernmost significant nesting area of the Least Sandpiper. Many birds nest around a single pond complex, which supports a lush vegetation that is heavily grazed by horses. Nests occur there and in nearby dry, sparsely vegetated habitat. Birds start arriving by mid-May (males first), and clutches (including replacement clutches) are completed in a period of 4–5 weeks, from late May to late June. Most eggs are laid in the morning, at intervals averaging 1.2 days. Incubation increases gradually through laying and is ~100% beginning with the last egg. Incubation lasts 20–21 days. Nest and chick mortality is high, mostly due to predation by Herring Gulls (Larus argentatus). Mortality of siblings is contagious. Females which nest successfully begin to migrate south by late June, followed by successful males in early July; individuals of both sexes are seen for about 3 days after the completion of parental behavior. Unsuccessful breeders leave earlier, and fledglings later. On average, males are seen for about 10 days and females for about 7 days following final breeding failure. Adults and fledglings tend to flock assortatively in late summer. General features of the breeding cycle seem to be highly conservative throughout the species' range.
Residues of DDE and PCB in Eggs from Herring Gull (Larus Argentatus) and Common Gull (Larus Canus) in Norway
