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Variation in the Juvenal Plumage of the Red-Legged Shag (Phalacrocorax gaimardi) and Notes on Behavior of Juveniles

Pamela C. Rasmussen
The Wilson Bulletin
Vol. 100, No. 4 (Dec., 1988), pp. 535-544
Stable URL: http://www.jstor.org/stable/4162642
Page Count: 10
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Variation in the Juvenal Plumage of the Red-Legged Shag (Phalacrocorax gaimardi) and Notes on Behavior of Juveniles
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Abstract

The juvenal plumage of the Red-legged Shag (Phalacrocorax gaimardi) was found to be highly variable individually and geographically, based on examination of 16 specimens, 23 birds in photographs, and observations of 48 living birds. Juveniles from the Pacific coast of South America ranged from very dark to pale-plumaged, while juveniles from the Atlantic coast were very pale in plumage color. Gular pouch color, foot color, and extent of filoplumes of the neck patch varied as well among juveniles. This variation supports recognition of the race P. g. cirriger for the Atlantic population, and may facilitate parental recognition in the Pacific population. Fledged juvenile Red-legged Shags creche below nest cliffs where their parents locate them for feeding; this behavior may be correlated with obligate cliff-nesting in small colonies.

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