INTERSEASONAL CHANGES IN SHOREBIRD HABITAT SPECIALIZATION IN MORETON BAY, AUSTRALIA

Habitat use by shorebirds in Moreton Bay was examined by monitoring 56 intertidal study sites during southward and northward migrations betw een 1988 and 1990. Sites were selected to include four areas in Moreto n Bay that had distinct intertidal habitats (mainland, island, coral a nd sewage habitats). At each site, the relative abundance of species w as recorded and habitat assessed using sediment particle size analysis and visual assessment of seagrass coverage. Spatial and temporal patt erns of habitat use were characterised by variation in the relative ab undance of species in habitats. Spatial and temporal patterns were int egrated by seeking patterns that could explain the variability in comm unity structure between different times of year, and that could be att ributed to temporal aspects of migration. Species diversity and measur es of habitat specialisation supported the prediction that shorebirds are more concentrated within preferred habitat during the northward co mpared with the southward migration in Moreton Bay, and that the size of this change is related to the respective degree of specialisation o f each species. The change between seasons may have been caused either by greater energy reserves of individual birds at the time of northwa rd migration or an increase in the ability of first-year birds to loca te suitable habitat by this time of year. The protection of all habita ts in Moreton Bay is required to conserve the full range of shorebird species using both the eastern and western portions of the Bay.