Continued expansion of the Wedge-tailed Shearwater, Puffinus pacificus, nesting colonies on Rottnest Island, Western Australia

The areas and burrow densities of Wedge-tailed Shearwater, Puffinus pacificus, colonies on Rottnest Island, Western Australia, were measured in April 2002. In the 10 years since the previous survey on Rottnest Island, two new colonies have been established. Summed over all colonies, there was an increase of 46% in the total area of colonies, to 45785 m2, and a doubling of the total number of burrows, to 11745 ± 1320 (s.e.). Burrow densities differed significantly between colonies and vegetation type. Burrow densities were lowest on the edge of the colonies, where the heath plant Olearia axillaris was present. The growth of the Wedge-tailed Shearwater colonies is consistent with the increase in reproductive effort observed in many other tropical, colonial-nesting seabirds in south-western Western Australian waters.