Sewage farms over the years have provided the birdwatcher with rare visitors and unusual breeding birds. Aylesbury Sewage Farm in Buckinghamshire has attracted a number of interesting species during three years of regular observations. The chief aim of this study is to give a quantitative account of the bird-life associated with each phase of the water purification process and to show how the provision of artificial nest sites and control of grass-burning can increase the wildlife potential.