Interseasonal Changes in Shorebird Habitat Specialisation in Moreton Bay, Australia

Abstract

Habitat use by shorebirds in Moreton Bay was examined by monitoring 56 intertidal study sites during southward and northward migrations between 1988 and 1990. Sites were selected to include four areas in Moreton Bay that had distinct intertidal habitats (mainland, island, coral and sewage habitats). At each site, the relative abundance of species was recorded and habitat assessed using sediment particle size analysis and visual assessment of sea-grass coverage. Spatial and temporal patterns of habitat use were characterised by variation in the relative abundance of species in habitats. Spatial and temporal patterns were integrated by seeking patterns that could explain the variability in community structure between different times of year, and that could be attributed to temporal aspects of migration. Species diversity and measures of habitat specialisation supported the prediction that shorebirds are more concentrated within preferred habitat during the northward compared with the southward migration in Moreton Bay, and that the size of this change is related to the respective degree of specialisation of each species. The change between seasons may have been caused either by greater energy reserves of individual birds at the time of northward migration or an increase in the ability of first-year birds to locate suitable habitat by this time of year. The protection of all habitats in Moreton Bay is required to conserve the full range of shore-bird species using both the eastern and western portions of the Bay.