This unique title evaluates the results from one of the most significant long-term studies of birds in the late twentieth century. The authors evaluate the working of natural selection on Snow Goose plumage colour, seasonal timing of breeding, clutch size, egg size and body size. With information gathered over 26 years on 40,000 individually marked adult geese, 45,000 nests and more than 110,000 goslings at one colony in northern Manitoba, this work is a landmark in avian biology and population genetics.