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1 October 2013 Replacement Rules for the Flight Feathers of Yellow-Billed Cuckoos (Coccyzus americanus) and Common Cuckoos (Cuculus canorus)
Sievert Rohwer, Kristin Broms
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Past studies of the replacement rules for flight feathers of cuckoos have been plagued by the erroneous assumption that the primaries constituted a single molt series. Instead, we show that the primaries of the Yellow-billed Cuckoo (Coccyzus americanus) are divided into three molt series and those of the Common Cuckoo (Cuculus canorus) into four series and, further, that Yellow-billed Cuckoos replace their rectrices in two molt series. Multiple molt series make it impossible to consistently describe primary replacement as a unique sequence of feather loss, as earlier researchers have attempted to do for cuckoos. We calculated the mean number of days (± SE) required to replace the primaries in each molt series. Primary replacement takes considerably less time in the larger Common Cuckoo than in the smaller Yellow-billed Cuckoo, mostly because Common Cuckoos replace four primaries at a time whereas Yellow-billed Cuckoos replace only three at a time. The primaries of Common Cuckoos cannot be better allocated into four molt series such that the time required for their replacement would be reduced, but molt duration would be reduced in Yellow-billed Cuckoos if their primaries were differently allocated into three replacement series. Both species replace their primaries faster than birds of similar size whose primaries are organized in a single replacement series.

© 2013 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,
Sievert Rohwer and Kristin Broms "Replacement Rules for the Flight Feathers of Yellow-Billed Cuckoos (Coccyzus americanus) and Common Cuckoos (Cuculus canorus)," The Auk 130(4), 599-608, (1 October 2013).
Received: 11 July 2013; Accepted: 1 September 2013; Published: 1 October 2013
Coccyzus americanus
Cuculus canorus
life history evolution
molt methods
multiple replacement series
transilient molt
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