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The present study was undertaken to compare the inheritance of behavioral and morphological features of two closely related species of Anas, and to attempt to establish whether any significant degree of behavioral variation occurs in the second generation which could be attributed to these genetic processes.
Two closely related species of Anas, the Common Mallard (A. p. platyrhynchos) and the Common Pintail (A. a. acuta), were selected for study. Both species have been repeatedly hybridized in captivity (GRAY, 1958; PHILLIPS, 1915, 1921), and occasionally hybrids occur in the wild. MAYR (1963) has commented on the fact that these sympatric Holarctic species have complete interspecific hybrid fertility, have a combined world population possibly exceeding 1000,000,000 and yet the rate of natural hybridization is probably less than one in several thousand. Thus, isolating mechanisms other than hybrid sterility, which presumably consist primarily of plumage and behavioral differences, are effective in maintaining the two species as distinct entities.