The development of endothermy in American White Pelicans

Abstract

We examined the development of endothermy in White Pelican (Pelecanus erythrorhynchos) chicks during the first 16 days after hatching, which corresponds with the age at which parent pelicans begin to cease brooding behavior. At ambient temperatures between 20 and 25°C, pelican chicks progressively increased their thermoregulatory capabilities with age; average thermal competence increased with each age increment while average cooling rates declined with each age increment. Thermoneutral metabolic rates increased initially with age, reaching a maximum at day 10, then declined. Whole body conductance and minimum conductance generally declined with age. Our results suggest that, although pelican chicks reach a modest degree of incipient endothermy by day 7, thermoregulatory self-sufficiency is not well developed until day 16. The age at which endothermy becomes well developed in pelicans is similar to those reported for other large pelecaniform species.