Molt strategies of ten neotropical forest passerine species

Abstract

We describe the number of inserted molts in the annual molt cycle and topographies resulting from the preformative molt in 10 Neotropical forest passerine species. Seven species showed two annual molt peaks, one in early spring (Mar–Apr) and one in late summer (Jul–Sept). The spring molt consisted of a light replacement of body feathers in <20% of individuals in our sample, and would be most consistent with a prealternate molt. We found two modes of preformative molt feather replacement where the “general mode” included all feathers of an anterior wing-tract being replaced before proceeding to the next posterior tract; the general mode was shown by all 10 species at moderate to high frequencies (69–99%). Seven species at low to mid frequencies (1–31%) exhibited “proximal mode” to include all wing feathers adjacent to the body replaced prior to distal feathers. Mean molt angle (a measure of direction of the replaced feathers when placed on a Cartesian plane) ranged from 12° to 24° and was higher in the “general mode.” An expanded phylogenetic analysis examining the extent of preformative molt that included the 10 study species plus an additional 18 Neotropical species suggested that ecological adaptations may have a greater influence over molt strategies than phylogenetic constraints at least in some of the families we examined.