ENERGY ALLOCATION AND POSTNATAL GROWTH IN CAPTIVE ELEGANT TERN (STERNA ELEGANS) CHICKS: RESPONSES TO HIGH-VERSUS LOW-ENERGY DIETS

Abstract

Abstract Effects of variable energy intake on chick growth, organ development, and gut-passage time in seabirds were investigated by raising Elegant Tern (Sterna elegans) chicks in the laboratory on three diets involving a major prey species, northern anchovy (Engraulis mordax), and a minor prey species, topsmelt (Atherinops affinis). Anchovies are ∼25% higher in energy content than topsmelt and represent a more abundant but highly fluctuating prey resource. Chicks were raised from age 15 to age 35 days posthatch on one of three diets (n = 8): (1) high-energy anchovy at the average daily intake rate, (2) low-energy topsmelt at the same intake rate, and (3) high-energy topsmelt (i.e. at a biomass equal in energy content to the anchovy diet). Chicks raised on the high-energy anchovy diet had a significantly faster gain of body mass and wing length. All three groups, however, had attained a statistically similar wing length at 35 days posthatch and did not differ in lean dry mass or pectoral muscle mass, ind...