Vertebrate fauna associates of the Wedge-tailed Shearwater, Puffinus pacificus, colonies of Rottnest Island: influence of an ecosystem engineer

Abstract

Wedge-tailed Shearwaters, Puffinus pacificus, engineer the ecosystem by digging burrows in which they nest. This has been previouslyshown to affect the soil and vegetation properties of their colonies. Here we report on field surveys employed to investigate how associatedvertebrate fauna respond to physical habitat modification by shearwaters. The study area was species poor, with only one mammal, andthree reptile species detected in 1440 Elliott trap and 720 pitfall trap nights across a 13-month period. Nineteen bird species were recordedfrom 98 survey days. Relative to an area of uncolonised heath, we observed an increase in the abundance of King's Skinks, Egernia kingii,and a decrease in the abundance of House Mice, Mus musculus, and West Coast Ctenotus, Ctenotus fallens, in the shearwater colony. Thesurvival rates of King's Skinks and House Mice were not affected by Wedge-tailed Shearwater presence. Bird species richness was less in thecolony (9.2 ±0.5 species month-I) than the heath (11.5 ±0.2 species month-I), and the composition of the two communities was different.We suggest that ecosystem engineering by Wedge-tailed Shearwaters is a major determinant of fauna associates of their colonies and offerdirect and indirect mechanisms to explain the patterns of species occurrence observed.