No evidence of food limitation during the breeding season of a freshwater marsh-nesting tern

Abstract

ABSTRACT Food availability is considered an important limiting factor in the breeding performance of marine birds, which exhibit restraint in reproductive life-history characteristics (e.g., delayed maturation, small clutch size, slow growth). Less well understood, however, is the extent to which taxonomic analogue species that breed in freshwater habitats are similarly regulated by food availability. Marsh-nesting Forster's Terns (Sterna forsteri) were studied from 2004 to 2008 at Horicon Marsh, a freshwater colony site in Wisconsin, USA, where reproductive success has been chronically poor. The adequacy of the food base to support a breeding colony of terns was evaluated (1) indirectly, through measures of breeding performance correlated with food availability during the egg-laying and incubation stages; and (2) directly, through a supplemental feeding experiment, conducted in 2004 and 2006, to determine whether nestling growth was limited by food availability. Clutch size, egg size, and adult body cond...