Hybridization in meadowlarks. Bulletin of the AMNH ; v. 134, article 1

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New York : [American Museum of Natural History]
"Previous studies of the comparative biology of the eastern meadowlark (Sturnella magna) and the western meadowlark (S. neglecta) have revealed that these sibling species are virtually, if not completely, isolated throughout a rather narrow zone of sympatry from central Mexico to the Great Lakes region of the United States. A case of hybridization of the two species in New York is fully substantiated by the capture of both adults and their hybrid offspring, and by the subsequent analysis of the morphology and vocalizations of the captive birds. Another hybrid, from Quebec, was also raised in captivity and is included in this analysis. A total of six hybrids are reported on here, all of which represent the first generation of hybrids produced by crossings in the wild of neglecta males with nominate magna females. No data are currently available on the reciprocal cross or on populations of magna other than the nominate race. Attempts to breed and to hybridize these captive individuals have failed. Morphologically, the first generation of hybrids of this particular cross are phenotypically indistinguishable from the magna parent with respect to those characters that depend on the intensity of melanic and carotenoid pigmentation, but are intermediate between the parental types with respect to the sexually dimorphic characters, including cheek color and mensural characteristics. Mensural characters are useless as indices of hybridization except for the elimination of 'extreme' specimens. All hybrid males from this cross should be identifiable by the concordance of a prominent yellow area on the cheek with an overall dark plumage coloration. The same characters must be used for females, but with considerably less confidence. The size of the repertoire of primary song patterns shows some promise as a clue for the field identification of hybrid males, but the actual patterns of primary song are meaningless for this purpose. Conflicting evidence on the call notes of hybrids necessitates further experimentation in this area and, at present, precludes their use for the identification of hybrids in the field. The results of this study make it clear that hybrid meadowlarks can be identified with accuracy and authority only on the basis of a prior knowledge of the phenotypic recombinations of specific characters in hybrids of known parentage"--P. 24.
25 p., 8 p. of plates : ill. (some col.) ; 27 cm.
Includes bibliographical references (p. 24-25).