A survey of wetland-associated birds was conducted in 100 ha of wet saltmarsh and its associated ecotonal areas at Twelve Mile Creek from September 2004 to April 2006. The hydrological changes from the seasonal flow of tides and fresh water across the saltmarsh and its surrounds are described. The resulting dynamic mosaic of complex wetland habitats supported many aquatic species and one of the three known small regional subpopulations of the Endangered Capricorn subspecies of the Yellow Chat Epthianura crocea macgregori (Houston et.al. 2004a). The survey yielded 64 bird species, including 31 migratory species, mainly present during the wet season (December to March). They included specialised terrestrial and wetland-associated species and some that use both fresh or saline habitats. Five rare or threatened species (Radjah Shelduck, Cotton Pygmy-goose, Black-necked Stork, Capricorn Yellow Chat, Glossy Black Cockatoo) used the wetlands, or the adjacent woodlands, some raising their young. Fifteen species of migratory waders used the area and, on one occasion, the numbers of Sharp-tailed Sandpipers present during their northward migration reached the criterion for significant flyway staging habitat. Terrestrial species records included the Bar-breasted Honeyeater which extended its breeding range south. The diversity of rare or threatened species and migratory species within the study area confirms Twelve Mile Creek wetland as important habitat for birds and of high conservation significance. This result enhances the intrinsically high conservation value of the unique structural complexity of its saltmarsh vegetation within the Fitzroy Delta. Potential threats include industrial expansion, over-grazing and loss of creek surface water in-flows. The latter may be particularly significant based on observations of the saltmarsh habitat and associated dependent fauna (i.e. Yellow Chat) suggesting a link between productivity of the system and freshwater in-flows. Current and future uses and tenures of the land are discussed because they affect future conservation management.