Some Morphological Features of Avian Kidneys

Abstract

Morphologic data pertaining to the kidneys of 181 species of birds are presented. An inverse relationship was found between kidney and body weight. Kidneys from relatively small birds generally exceeded 1% of body weight; the reverse was true in larger birds. Kidney to body weight ratios varied over a range from 6 to 21 mg/g, and were generally consistent intraspecifically. No difference was detected in relative kidney size between the sexes. The kidneys studied were divided into 5 categories descriptive of variations in external configuration. Obscurity of the middle lobe (especially marked in Passeriformes) appears to result from its close association with the other lobes, particularly the caudal. Direct mesial continuity (fusion) of the kidneys was relatively common, and typically involved the caudal lobes.