Western Port consists of rocky platforms, sandy beaches and marine habitats. It is home to a diverse range of invertebrates including colonial ascidians, sponges and corals. Mudflats and mangrove swamps around the northern end of the bay support a large number of invertebrates that are an important food source for waders and visiting migratory birds. French Island is home to migratory waders, Australian pelicans, short-tailed shearwater rookeries, and many other significant fauna species. The bay has been identified as a 623 km2 Important Bird Area (IBA) by BirdLife International because it regularly supports small numbers of critically endangered orange-bellied parrots, over 1% of the world populations of Far Eastern curlews, red-necked stints and pied oystercatchers, and declining numbers of vulnerable fairy terns.