Abstract
Summary Day, D. H. 1977. A morphological study of Yellow-billed Duck and Red-billed Teal. Ostrich Suppl. 12:86–96. Measurements were made of Yellowbilled Duck Anas undulata and Redbilled Teal A. erythrorhyncha (100 male and 100 female birds of each species) caught for ringing at Barberspan Ornithological Research Station 26 33S; 25 36E in the western Transvaal. The sexes (originally determined by cloacal examination) can be separated morphologically in the field. Males are larger than females in length and differ from females also in the colouration of the bill and extent of the speculum.
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