Birds of Indian Subcontinent

Subadult Plumage in the House Finch and Tests of Models for the Evolution of Delayed Plumage Maturation

Publication Type:Journal Article
Year of Publication:1996
Authors:Hill, GE
Journal:The Auk
Date Published:1996
ISBN Number:00048038
Keywords:Burrica, Burrica mexicana, Carpodacus, Carpodacus mexicanus, Fringillidae, Haemorhous, Haemorhous mexicanus, Mexico
Abstract:In many passerine species males do not attain definitive breeding plumage until after their first potential breeding season. Such delayed plumage maturation has been the subject of numerous studies, most of which have focused on the adaptive value of female-like plumage for young males in single populations. Thus, although studies of delayed plumage maturation have been presented as tests of evolutionary hypotheses, most have lacked an appropriate comparative perspective. Moreover, most studies of subadult plumage in passerines have been conducted without information on the general function of ornamental plumage in the species being studied. A study of delayed plumage maturation in the House Finch (Carpodacus mexicanus) provided an opportunity to overcome these problems. The function and proximate control of ornamental plumage coloration in House Finches have been studied extensively. In addition, House Finches occupy a wide range across North America with approximately 15 subspecies recognized, and populations vary in expression of delayed plumage maturation. In most populations, including the most familiar subspecies, C. m. frontalis, males acquire definitive basic plumage in their first prebasic molt. In at least three populations, C. m. griscomi of southern Mexico, C. m. amplus of Guadalupe Island, and Great Basin populations of C. m. frontalis, however, males do not acquire definitive plumage until the completion of their second prebasic molt, spending their first potential breeding season in a female-like plumage. Using a composite phylogeny and parsimony analysis, I show that delayed plumage maturation likely was lost in the ancestral House Finch population and was regained independently by the three taxa in which it is now observed. Thus, delayed plumage maturation in the House Finch is a derived trait. In addition, I show that the acquisition of delayed plumage maturation is associated with a reduction in the extent of ornamental plumage (i.e. a reduction in patch size). These observations support the idea that delayed plumage maturation in the House Finch is an adaptation to increased production costs of red ornamental display plumage in some populations.
Short Title:The Auk
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