Evidence for a prealternate molt-migration in the Rufous Hummingbird and its implications for the evolution of molts in Apodiformes

Abstract

ABSTRACT An inserted body-feather molt has recently been documented in the Ruby-throated Hummingbird (Archilochus colubris) during its southbound migration; however, it is unknown whether other species of hummingbirds undergo similar inserted molts or molt-migrations. We examined 346 specimens of Rufous Hummingbird (Selasphorus rufus) collected throughout its range and found evidence for a previously unrecognized, inserted body-feather molt that appears to occur, at least partially, at stopover locations in California and the Mexican monsoonal region. This limited molt occurs in all young and in most (but not all) adult Rufous Hummingbirds, primarily in late June through October, before the complete overwinter molt in February–March. The location, timing, and extent of this molt in the crown, back, and underpart tracts showed similar patterns among the 4 age–sex groups; however, patterns of inserted throat-feather molt differed, occurring in all young birds and some adult females but not in adult males. I...