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1 April 2011 How Much Variation in the Molt Duration of PasserinesCan Be Explained By the Growth Rate of Tail Feathers?
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In birds, molt duration is an important trait that can affect plumage functionality and, consequently, the fitness of individuals. However, knowledge about the factors that affect variation in molt speed is sparse, mostly because of the methodological difficulties of studying avian molt. We used a ptilochronology-based approach to estimate the rate at which tail feathers were produced during molt to shed light on the relationship between molt duration and feather growth rate. For that purpose, we used three data sets. First, we tested whether the average molt durations of 22 passerine species were correlated with the mean growth rates of their feathers, using both conventional and phylogenetically corrected statistical procedures. Second, we explored this same association among captive Great Tits (Parus major). And third, we took advantage of the biannual complete molt of Willow Warblers (Phylloscopus trochilus) to examine whether the feathers synthesized during their short summer molt grew faster than those produced during their long winter molt. Feather growth rates were negatively correlated with molt duration in all analyses, revealing that molt duration can be estimated from the growth rate of a single feather. However, predictive power was limited by the fact that molt duration is modulated mainly by molt intensity, which seems to be correlated with ecological constraints in our interspecific approach. We also discuss the implications of our results for the evolution of molt duration, and the potential application of ptilochronology in its study.

© 2011 by The American Ornithologists' Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website,
Iván De La Hera, Sonja V. Schaper, José A. Díaz, Javier Pérez-Tris, Staffan Bensch, and José Luis Tellería "How Much Variation in the Molt Duration of PasserinesCan Be Explained By the Growth Rate of Tail Feathers?," The Auk 128(2), 321-329, (1 April 2011).
Received: 2 August 2010; Accepted: 1 December 2010; Published: 1 April 2011

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