A Five Year Study of Wedge-tailed Shearwater and Black Noddy Census Data in the Capricorn/Bunker Group, Great Barrier Reef

Wedge-Tailed Shearwater Puffinus pacificus and Black Noddy Anous minutus nest censuses exist for various islands of the Capricorn Group but few were completed on multiple islands in the same breeding season. There is no cumulative spatial information for these species in any single breeding season, or for the group of islands as a whole over time. The purpose of this study was to report baseline information on the size and distribution of these populations and to establish a cost effective program for monitoring the status of these numerically dominant seabird species of the Great Barrier Reef. Our burrow censuses of the wedge-tailed shearwater indicate small population fluctuations between years though most changes fell within expected ranges based on standard errors. Differences were found between some years on Tryon and West Fairfax Islands. The census results for Noddies exposed a weakness in the methods for North West Island and Wilson Island associated with a patchy population distribution. However, the results for other islands were acceptable and showed a dynamic equilibrium for islands other than Heron Island. On Heron Island the Black Noddy population more than halved from approximately 70,000 to approximately 30,000 over the five years. Understanding the dynamics of populations is important if we are to understand the impact of environmental and human factors over time. Single ad hoc censuses cannot provide these patterns in population dynamics. This five year study has provided enough baseline information to formalise an easily replicated methodology to assess the effects of human or ecological impact on these populations