Peter Pyle
Adult hummingbirds were formerly thought to undergo only a single prebasic molt per year, but prealternate molts have recently been documented that may or may not include the bright and iridescent feathers of males. I examined 2,738 images of the Bee Hummingbird Mellisuga helenae at the Macaulay Library. Among images of 653 males and 135 females, I documented prealternate molt occurring in adults, during which the iridescent red gorget feathers of males were completely replaced with non-iridescent feathers in July-September and replaced again with iridescent feathers in December-January. Molt of flight feathers occurred in October-December. I defend a terminology whereby the first replacement of body feathers is part of a definitive prealternate molt. I further suggest that cryptic coloration due to loss of the gorget feathers may have evolved for predation avoidance or reduction of territorial disputes during a vulnerable period in which primaries are being replaced.