Molt Cycles of the Orange-Crowned Warbler

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Abstract
The present study of molt in the orange-crowned warbler (Vermivora celata) is based on 2155 museum specimens taken in all months of theyear and from a wide range of breeding and wintering localities. The partial postjuvenal molt usually replaces only the body plumage, tail coverts, and alar coverts except the greater primary coverts. However, evidence of limited replacement of certain flight feathers also was found. Most commonly renewed are flight feathers which occupy the exposed portions of the tail and wings and are, therefore, most vulnerable to wear. The molt occurs on the breeding grounds before the fall migration in all races except sordida. In the latter ssp., evidence suggests that molt occurs after migration. The prenuptial molt usually involves only areas of the head and chin. The number of individuals molting varies geographically among the sspp. and within each ssp. V. c. sordida has no prenuptial molt. Variation in the number of individuals in each sex-age group that undergoes a prenuptial molt may be correlated with the variation in frequency of occurrence of the orange crown patch. Categories with the lowest proportion of individuals with orange crowns before the molt have the highest proportion of molting birds. The postnuptial molt is complete and occurs on the breeding grounds between the time of breeding and the fall migration, taking approximately 2 months in an individual. A survey of spp. of Parulidae from North America revealed that the extent of the postnatal, postjuvenal, and postnuptial molts is quite uniform in the family, but that the extent of the prenuptial molt varies considerably. Such variation appears to be adaptive at the sp. level and does not always reflect generic relationships defined by other criteria.