Pterylography and Age Determination in the Orange-Crowned Warbler

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Abstract
Down feathers of orange-crowned warblers (Vermivora celata) are variously distributed, the number in any region differing among birds and on the same bird between members of paired tracts. In each developing feather tract, growth begins centrally and moves laterally. The tracts are nearly completed when the stub-tailed young leave the nest approximately nine days after hatching, although most feathers carry at least a basal sheath. Slight variations occur in definitive pterylography between juveniles and the older age groups. The pterylography of this sp. also differs from that of the yellow-throat (Geothlypis trichas brachidactylus), the only other parulid whose pterylography has been studied in detail. Differences between these 2 spp. occur in the number of wing coverts, number of tail coverts, density of feathers in the crural and patagial areas, and configuration of several of the major tracts. A method of aging the birds by use of plumage characteristics was established. Immature and first-year birds have primaries with tips narrower and more centrally pointed than those of adults, whose primaries tend to be both wide and blunt. Furthermore, feathers of immature and first-year birds wear much more extensively than do those of the adults.

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