Dr. H. J. Frith has studied the ecology of a number of birds and mammals, notably the grey teal and other species of water fowl, the mallee hen, several species of pigeons and the red kangaroo. His work on the grey teal stands as a uniquely documented contribution to the ecology of opportunistic species. It is relevant to the current dialogue about the control of natural populations which is an important frontier in the theory of population ecology. All of Frith's work has the same quality which comes from tackling, with ingenuity and insight, important ecological problems in a broad and completely natural setting.