Relationships between kidney mass and body size in some Anseriformes

Relationships between kidney mass (KM) and body mass (BM), body length (BL), and sternum length (SL) were studied in adults of both sexes of 4 Mergini anseriforms: Clangula hyemalis (n = 74), Melanitta fusca (n = 29), M. nigra (n = 15), and Somateria mollissima (n = 8). The following indices were established for the four species and for the Mergini tribe: KM/BM (as per cent body mass), KM/BL, and KM/SL. Additionally, allometric equations describing the relationships studied were developed for the tribe using mean kidney weights and body parameters of males and females of the species examined. The KM/BM indices for several anseriform tribes (i.e. Anserini, Anatini, Aythyini and Mergini), differing in food and feeding modes, were determined, based on the literature data and those obtained in this study. In addition, an allometric equation describing the kidney weight-body weight relationship in the Anseriformes order was developed as log KM = 0.797 log BM-1.346 (n = 22). The relative kidney size in the sea duck species studied showed significant intra- and interspecific differences. In addition, clear between-tribes differences in KM/BM were revealed. The highest value (1.57%) of the index is typical of the Mergini, grouping diving carnivorous sea ducks, while the lowest index (0.65%) is typical of the Anserini, a tribe which groups non-diving herbivorous birds.