First-cycle molst in North American Falconiformes. Pyle, P. Journal of Raptor Research, 39(4):378-385, 2005.
abstract   bibtex   
.--I examined 1849 specimens of 20 North American Falconiform species to elucidate the occurrence and nomenclature of partial first-cycle molts. As reported in the literature, American Kestrel (Falco sparverius) and White-tailed Kite (Elanus leucurus) have relatively complete body-feather molts that occur during the first fall; in the kite, this molt can also include up to all rectrices and 2-6 secondaries, but no primaries--an unusual pattern for such partial molts in first-year birds. Evidence of partial first- cycle molts was found in 16 of 18 other species (among Pandion, Haliaeetus, Circus, Accipiteg, Asturina, Buteo, Aquila, and Falco) for which such molts have not been previously elucidated. Maximum extent of body-feather replacement among individuals of these 16 species varied from 5-50%. On the other hand, most species showed evidence that this molt could be absent (11-100% of birds remaining in juvenile plumage until commencement of the complete or near-complete prebasic molt that occurs during the first summer). I argue that these partial molts are best considered preformative molts (following Howell et al. 2003) rather than "first prebasic" molts, as defined by Humphrey and Parkes (1959). Variation in the extent and timing of preformative molts may reflect various constraints according to species- specific breeding, migrating, and foraging strategies. The apparent lack of function for this molt suggests that ancestral Falconiformes exhibited a more extensive preformative molt, as found in related orders of birds, but that this molt has since become vestigial, at least in the larger specie
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 title = {First-cycle molst in North American Falconiformes},
 type = {article},
 year = {2005},
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 keywords = {American Kestrel,Elanus leucurus,Falco sparverius,White-tailed Kite,falcons,hawks,preformative molt},
 pages = {378-385},
 volume = {39},
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 abstract = {.--I examined 1849 specimens of 20 North American Falconiform species to elucidate the occurrence and nomenclature of partial first-cycle molts. As reported in the literature, American Kestrel (Falco sparverius) and White-tailed Kite (Elanus leucurus) have relatively complete body-feather molts that occur during the first fall; in the kite, this molt can also include up to all rectrices and 2-6 secondaries, but no primaries--an unusual pattern for such partial molts in first-year birds. Evidence of partial first- cycle molts was found in 16 of 18 other species (among Pandion, Haliaeetus, Circus, Accipiteg, Asturina, Buteo, Aquila, and Falco) for which such molts have not been previously elucidated. Maximum extent of body-feather replacement among individuals of these 16 species varied from 5-50%. On the other hand, most species showed evidence that this molt could be absent (11-100% of birds remaining in juvenile plumage until commencement of the complete or near-complete prebasic molt that occurs during the first summer). I argue that these partial molts are best considered preformative molts (following Howell et al. 2003) rather than "first prebasic" molts, as defined by Humphrey and Parkes (1959). Variation in the extent and timing of preformative molts may reflect various constraints according to species- specific breeding, migrating, and foraging strategies. The apparent lack of function for this molt suggests that ancestral Falconiformes exhibited a more extensive preformative molt, as found in related orders of birds, but that this molt has since become vestigial, at least in the larger specie},
 bibtype = {article},
 author = {Pyle, Peter},
 journal = {Journal of Raptor Research},
 number = {4}
}

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