Goose counts from aerial photographs using an optical digitizer

Abstract

Accurate population estimates are essential for waterfowl management. However, most waterfowl population surveys are made ocularly from aircraft, resulting in visibility and observer biases (Caughley 1974, Erwin 1982). Bias is of particular concern on waterfowl wintering and staging areas where concentrations may exceed 1 million birds. Vertical aerial photography has been used effectively in waterfowl surveys (Chattin 1952, Heyland 1972), but counts from photographs require many hours of analysis. This paper describes a rapid and accurate technique for estimating numbers of geese by analyzing aerial photographs with an optical digitizer.