Nearest neighbour analysis and spatial relationships of Wedge-tailed Shearwater, Puffinus pacificus (Aves: Procellariiformes), burrow entrances at Radar Reef, Rottnest Island, Western Australia

The spatial distribution of Wedge-tailed Shearwater burrow entrances on Rottnest Island, Western Australia, was investigated using the single- and two-sector nearest neighbour methods ofpoint pattern analysis. Both analyses yielded similar results. Mean burrow density was 0.32 ±0.02 SE burrows m-2, burrow entrances were not distributed at random and entrances tended towards an even distribution. Evenness ofdistribution was positively correlated with burrow density. Social and structural factors are likely to be important in determining burrow entrance distribution by Wedge-tailed Shearwaters and there appears to be a density-dependent trade-off between social benefit (aggregated burrow entrances at low densities) and colony stability (evenly distributed burrow entrances at high densities).