Changing habitat has both resulted in a decline in some bird species and benefited the populations of other species. Sydney has lost several species through habitat degradation or alteration. Urban development has caused a drastic reduction in the local heath environment. The only surviving areas are those protected today by national parks and recreational areas. We have lost local populations such as the heath-frequenting Ground Parrot Pezoporus wallicus and Eastern Bristlebird Dasyornis brachypterus and more recently Southern Emu-wren Stipiturus malachurus. In woodland and modified areas the Jacky Winter Microeca fascinans has lost its struggle against development.

Once forests covered a large area of Sydney's hinterland. Removal of the largest remaining tracts of native bush was as recent as 80 years ago. Not all has been lost: the recent acquisition of remnant native bush through national parks and other protected areas provides a variety of environments where native birds are still plentiful. A quick classification of habitats is provided by Morris (1996), who recognised seven forms: coast, harbour, foreshores, heath, forest, woodland, and modified. Two further habitats are wetlands and suburban gardens.