HABITAT VARIATION IN THE SOCIAL-ORGANIZATION OF A COMMUNAL GALLINULE, THE PUKEKO, PORPHYRIO-PORPHYRIO-MELANOTUS

1. The social organization and dispersal of pukeko or swamphen, Porphyrio porphyrio melanotus, was studied in two different habitats in the Manawatu, New Zealand. 2. A non-territorial flock formed each summer in the swamp-lake habitat complex and fed in the pasture of breeding territories. Flocks had a high proportion of males and young. Most dispersed prior to the breeding season although some birds remained, set up territories, and attempted to breed. Such flocks did not form in the stream-pasture habitat complex. 3. The remaining birds in both areas held territories for at least the breeding season with the number of individuals in a territory varying from two to six. Pairs were common in the stream-pasture habitat whereas groups predominated in the other swamp-lake habitat. The number of birds in a territory related to the length of the defended boundary and its stability. Within each group, pair with young, and flock a linear hierarchy was found with status related to age, sex and prior residence. 4. Pukeko satisfy many of the criteria suggested by Brown (1974) which lead to communality. The number of birds in a group appears to relate to the costs of territorial defence which is in turn linked to habitat structure. Variations in the spatial organization are related to theories of a continuum of social organization regulating access to resources. © 1979 Springer-Verlag.