LATITUDINAL VARIATION IN THE BODY-SIZE OF SPARROWHAWKS ACCIPITER-NISUS WITHIN BRITAIN

On the basis of Sparrowhawks Accipiter nisus found dead in various par ts of Britain during 1979-1991, wing-length was found to provide the m ost reliable index of overall body-size because it gave the best and m ost consistent correlations with five other measures of body-size. A m arked latitudinal trend in the body-size of Sparrowhawks was found wit hin Britain, with birds of each sex and age group increasing in size f rom south to north, in line with Bergmann's Rule. For each successive degree of latitude (approximately 110 km), winglength increased by an average of 0.86 mm in adult males and 0.75 mm in adult females. No obv ious west-east trend in body-size was found within Britain.