On the basis of Sparrowhawks Accipiter nisus found dead in various parts of Britain during 1979–1991. wing-length was found to provide the most reliable index of overall body-size because it gave the best and most consistent correlations with five other measures of body-size.
A marked latitudinal trend in the body-size of Sparrowhawks was found within Britain, with birds of each sex and age group increasing in size from south to north, in line with Bergmann's Rule. For each successive degree of latitude (approximately 110 km), wing-length increased by an average of 0.86 mm in adult males and O.75 mm in adult females. No obvious west-east trend in body-size was found within Britain.