Over the last 50 years major areas of bird habitat have been lost from the County of Cumberland. Included are the major saltmarshes and freshwater swamps from the western side of Botany Bay; the tall forests of the Upper North Shore and the woodlands of the Cumberland Plain between Parramatta and the Nepean. With this, major components of the former Sydney avifauna have become rare and at least eight species have been eliminated from the County as breeding species. Analyses are made of the avifaunas of these habitats as they existed in the 1930s and 1940s. It is confirmed that immediately a habitat goes so does the species dependent on it. Only one-third of the 108 forest and woodland species discussed occur in multiple habitats and hence are well insulated against change. The use of progressively degraded habitats is explored and it is found that only a very few species can persist once the process starts.
It is strongly argued that the key to understanding ecosystems and the biology and ecology of species is research: only when we understand how they operate, and their needs, can we minimize the impact and predict the impact of changes.
An extensive segment of the article is devoted to painting a word picture of habitats, familiar to the writer in the 1930s and 1940s, that are now extinct.