Home Ranges and Group-territoriality in Chowchillas Orthonyx spaldingii

Abstract

Summary: Chowchillas live year-round in groups of 2-5 birds, cooperate in territory defence and forage in groups. This study of social behaviour, territory defence and home range use was facilitated by the use of radio-telemetry. A single bird in each of five groups was fitted with a radio-transmitter to locate birds that are otherwise difficult to find in the rainforest. Two groups were tracked for 10-24 months so that seasonal changes in home range use could be investigated, while five groups were followed for two months to examine interactions between neighbouring groups. Different methods of representing home ranges and patterns of utilisation were compared. The home ranges of Chowchillas were found to be substantially larger than the areas that they defended from neighbouring groups, and there was considerable overlap in the home ranges of neighbouring groups. Chowchillas shifted their favoured foraging areas from season to season, tending to avoid areas where they had recently foraged. Home ranges of neighbouring groups encroached very little on the favoured foraging areas of other groups and territories were also virtually non-overlapping. These findings have implications for other studies of group-territorial birds where areas of use are commonly estimated from defended areas. As found in other studies of group-territorial birds, home range size increased with group size. Chowchillas provide an ideal opportunity for examining the costs and benefits of group-territoriality since they appear not to be cooperative breeders, unlike most other known group-territorial species.