Jankowiak Ł., Polakowski M. 2011. Biometrics of non-breeding immature Mallards (Anasplatyrhynchos) in north-eastern Poland. Ring 33, 1-2: 47-53. Non-breeding immature Mallards from north-eastern Poland (Północnopodlaska Lowland) were captured and measured (altogether 182 individuals in their 1st year of life). Immature males were significantly larger than females according to all analysed parameters. The length of bill and wing were the most sexually dimorphic traits and the least dimorphic were the total length of bill with head and tarsus length. The results of the present analysis and other studies in different regions of Europe suggest that wing size of Mallards follows Bergmann’s rule, while a bill size - Allen’s rule. Mallards from north-eastern Poland are larger than those from western Europe. We hypothesize that the reason for this is the fact that main population of non-breeding Mallards originates from the larger eastern European population, which is confirmed by some ringing data.
