Some causal and functional correlates of creching in young white pelicans

Publisher Website
Google Scholar
Abstract
Field observations and laboratory studies were conducted to examine the hypothesis that creching in white pelicans (Pelecanus erythrorhynchos) constitutes a substitute for parental protection from predators and thermoregulation. Pelicans began to form creches at 17 ± 2 days of age, in close correlation with temporary parental desertion of the nest. Once formed, creches were large and dense overnight when parents were normally absent from the colony, then broke up during the day when parents returned to feed their young. In the absence of parents, social attractions between young, facilitated by disturbance and a possible diurnal rhythm, accounted for the onset of creching. Density within creches, but not creche formation, was related to temperature. Creching began only after the young were too large to be molested by herring gulls, and no other sources of predation were seen. Laboratory measurements of oxygen consumption indicated a small (15.9%) but significant saving in energy from huddling at 10 °C, but not at 20 or 30 °C. This result suggests that energy saved by creching in the absence of parents could be an important function of overnight creching in this species. Some similarities and differences in creching in pelicans and adelie penguins are discussed.