Birds collected during the Whitney South Sea Expedition. 27, Notes on the variation of immature and adult plumages in birds and a physiological explanation of abnormal plumages. American Museum novitates ; no. 666

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New York City : The American Museum of Natural History
"Summarizing the results of the investigation of these plumages I can state the following facts: 1. The first-year plumage of Neolalage banksiana (Gray) shows two types of plumage: one, apparently more primitive, with a less intense pigmentation, which may be called a 'retarded' plumage; and the other approaching in pigmentation the adult dress, which may be called a 'progressive' plumage. 2. There is no clear-cut division between these two plumages; several specimens are intermediate in their characters. 3. There is a definite geographical correlation between the frequency of the two plumages on the various islands. On certain islands (as Efate and Aoba) all, or the majority, of the first-year birds wear a 'retarded' plumage; on other islands (as Santo and Malekula) all, or the majority, of the first-year birds wear a 'progressive' plumage. 4. The sexual dimorphism is frequently more pronounced in the first-year plumage than in the adult dress. Adult males and females are very much alike in this species, but the first-year plumage of the male is usually much more 'progressive' than that of the female. 5. The 'progressiveness' of an individual feather depends a great deal upon the time of its molt. Those feathers of the first-year plumage that grow first, as the wing-feathers and certain of the wing-coverts, resemble the adult feathers least. In some cases, feathers with a much more immature appearance (having grown earlier) can be found adjoining feathers with decidedly more adult characters. 6. The changing of the physiological status toward the adult condition can be observed in many individual feathers (particularly the tail-feathers). The tip of such a feather greatly resembles an equivalent typical immature feather, while the base is more like that of an adult feather. 7. Progressive feathers of the first-year plumage resemble adult feathers not only in pigmentation but frequently also in structure. This makes it quite difficult in extreme cases to decide whether a certain specimen is a first-year bird in 'progressive' plumage or an adult bird in 'retarded' plumage"--P. 7-8.
10 p. ; 24 cm.
Includes bibliographical references.