A SURVEY OF THE BREEDING SEABIRDS AND MIGRATORY SHOREBIRDS OF THE HOUTMAN ABROLHOS, WESTERN AUSTRALIA
| Posted: |
10/04/2021 |
| Author(s): |
Chris A. Surman, L. W. Nicholson |
A complete survey of the numbers and breeding stages of seabirds, resident and migratory shorebirds and raptors
at the Houtman Abrolhos Islands, central west coast, Western Australia, was undertaken. One hundred and ninety two
(192) islands, islets and rocks were surveyed over 21 days in December 2006.
Seabird nesting habitat was mapped in its entirety for those islands considered as significant breeding areas (i.e.
Pelsaert Island, Leo Island) and estimates of both breeding and roosting seabirds were made for each island. Notes on
the stage of breeding were also taken, and where applicable, eggs were measured and weighed for some species to
obtain breeding dates. Monitoring transects were established on West Wallabi and Pelsaert Islands to monitor longerterm
changes in the nesting density of the Wedge-tailed Shearwater Ardenna pacifica, Lesser Noddy Anous tenuirostris
melanops, Common (Brown) Noddy Anous stolidus and Sooty Tern Onychoprion fuscata. The Lesser Noddy transects
had been previously established by Fuller and Burbidge (1992), and were used again for comparative purposes.
We recorded 14 species of seabirds, 16 species of migratory shorebirds, three resident shorebirds and two raptors
during this survey. Of these, 14 species of seabirds, three resident shorebirds and the two raptors were breeding. These
breeding populations are considered significant in a regional and national context. Of the 192 islands surveyed, 148 (77
%) had breeding seabirds.
Population sizes had decreased in some species (Lesser Noddy, Sooty Tern, Common (Brown) Noddy, Wedge-tailed
Shearwater) and increased in others (Little Shearwater Puffinus assimilis, White-faced Storm-Petrel Pelagodroma
marina, Silver Gull Chroicocephalus novaehollandiae, Pacific Gull Larus pacificus) since the last survey undertaken in
1999. Some changes in breeding numbers were attributed to improved survey technology, but others reflected true
changes brought about by a range of factors including availability of tree nesting habitat and availability of food sources
to opportunistic species. Shifts in breeding times among some species (e.g. Bridled Tern Onychoprion anaethetus) were
also noted.
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