Niche segregation in sympatric short-tailed and wedge-tailed shearwaters

Global climate change has induced significant variations to the oceanographic landscape that has led to changes in the timing of breeding, breeding success and distributions of many marine species. Seabirds are apex marine predators that are strongly influenced by changes to their marine environment and ecosystem dynamics, with a number of Australian species demonstrating range movements and altered life history events in response to environmental change. The tropical wedge-tailed shearwater Ardenna pacifica has been increasingly extending its distribution southward across Australia’s east and west coast and now breeds sympatrically with the temperate short-tailed shearwater Puffinus tenuirostris at the most southerly known point of its range. This newly sympatric breeding environment offers the opportunity to examine patterns of niche segregation that may provide insight into the likely populational outcomes of each species under ongoing environmental pressure. This research employed nest monitoring techniques, geolocation devices and literature data to analyse segregation within three key domains of short-tailed and wedge-tailed shearwater ecology. The three principal areas of interest concerned the timing of breeding events, the use of foraging habitat and the diet composition and trophic positioning of each species. The results revealed little segregation within the timing of breeding events and trophic positioning between the species and pronounced spatial segregation when foraging at a distance from the colony. This study indicates the importance of robust environmental monitoring in preserving these species’ conservation status by determining the key features of future climatic change to which they are most vulnerable.