Occurrence and timing of second clutches in common terns.

Abstract

In Sterna hirundo, a 2nd clutch laid before chicks from the 1st brood fledged probably results from a physiological miscue associated with chick loss from the 1st brood and stimulated by an unusual surplus of food. When laid after chicks from the 1st brood fledge, a 2nd clutch might function as insurance, permitting a pair to raise young late in the season if chicks from the 1st brood are lost. In either case, parents must partition care between eggs and chicks from the 2nd clutch and fledged chicks from the 1st brood. Successful fledging of chicks from 2 broods in a single season is unlikely unless exceptionally favorable conditions occur. -from Authors