Sexing and aging silver gulls, Larus novaehollandiae

Abstract

Measurements of bill size differed between gulls from three widely separated Australian regions, suggesting that there are a number of different subpopulations. When assigning an individual to a sex, a geographical locality factor should be incorporated into the discriminant model. Bill colour may be a useful tool for ageing gulls and detailed colour categories have been identified which could be used to define relative ages. Free-flying gulls are here ascribed to one of seven categories. Colour categories may not be universal; therefore, the population should be considered region by region.