Early social influence on nestling development in Waldrapp ibis (Geronticus eremita)

Abstract

AbstractThe Waldrapp ibis is critically endangered; hence specific knowledge is needed to support the management of the last birds in the wild, and to prepare for reintroduction projects. In this study we attempted to test the effects of raising an ibis as a single chick from hatching to the age of 3 weeks, as compared to raising it together with nestmates, on development and juvenile socialization. In times of food shortage, interference competition between nestlings may cause quick starvation of all but the largest chick. In the context of establishing a free‐flying, semi‐tame colony of Waldrapp ibis at the Konrad Lorenz Research Station in Grünau, Austria, 12 zoo‐bred hatchlings were experimentally hand‐raised under ad libitum food conditions. Seven individuals were placed into three nests in visual and acoustical contact with each other to mimic a colony situation. Five others were raised in isolation their first 21 days after hatching and then were united with the sibling‐raised individuals in a colony‐like situation. After hatching, isolated chicks showed high frequencies of distress calls; they begged and ate less, put on less weight, and were less active than the socially‐housed chicks, and fledged an average of 6 days later. As the groups did not significantly differ in excreted corticosterone metabolites, we assume that the lack of social stimulation, rather than stress, caused the observed effects in the single‐raised chicks. After unification, individuals of both groups tended to stay apart from each other. Formerly single‐housed birds mainly interacted dyadically among themselves, whereas the sibling‐raised birds tended to have more varied contacts with colony members of different ages. The potential applications of these results to conservation and management are discussed. Zoo Biol 21:467–480, 2002. © 2002 Wiley‐Liss, Inc.