COMMUNAL ACTIVITIES AMONG WHITE-WINGED CHOUGHS CORCORAX MELANORHAMPHUS

White-winged Choughs Corcorax melanorhamphus live in groups of 2–20 birds that nest communally. Most of the study population (82%) was composed of groups of 4–8 individuals. The oldest male in each group appears to perform a ‘linchpin’ role in group cohesion, and groups tend to disintegrate if he dies or leaves. Polygyny is shown to occur, and it is thought that some 15% of clutches are due to two females laying in the same nest. Progeny tend to stay in their natal group rather than dispersing. They help to rear subsequent offspring. All group members may help to build the nest and to incubate, brood, guard, clean and feed the young (both in and out of the nest). No correlation was found between group size and the rate of feeding young in the nest. From 186 nesting attempts, the average production was 1–4 birds of which only 16% survived to adulthood (= 4 y. o.). Besides their nesting activities, White-winged Choughs have a form of communal defence; they, also, roost, forage, drink, bathe, dust, and roost together. It is concluded that the association into groups provides the adaptive advantage of a buffer against periodic fluctuations in available food– the youngest (= smallest investment) dying first.