Intraspecific and Interspecific Variation in Molt Patterns of Some Tropical Hummingbirds

Abstract

Sequences of flight-feather replacement were determined for 13 species of Costa Rican hummingbirds based upon capture-recapture data for 5 to 60 individually marked, adult individuals per species. A single sequence of primary molt occurred in 99% of all individuals, proceeding from innermost to outermost, except that the three outermost primaries molted in the sequence 8-10-9. For secondaries and rectrices, molt typically commenced with the innermost and/or outermost feathers and proceeded centripetally, but with much individual variation. Between 2 and 18 different sequences were observed in these tracts for the different species, the number of sequences per species being closely correlated with the number of molt records. Each species showed two or three common sequences and various rare ones; within at least one species, some individuals showed different sequences in successive annual molts. It is incorrect to postulate genetically fixed, rigid sequences of at least secondary and rectrix molt for these species, or even for individuals within a species. Bilateral asymmetry of feather replacement was very rare for primaries, but more frequent for secondaries and rectrices. For five species in which at least 30 records were available, the progress of molt over the entire plumage was examined, using primary molt as a standard. Molt in secondaries and rectrices commenced when four to six primaries had been replaced, and finished at about the same time as did primary molt. Wing and tail coverts commenced molt after, and finished before, the primaries. In all species, body molt proceeded continuously throughout the period of primary molt, with minor differences in timing in different tracts being far exceeded by individual variation. The major difference between species occurred in the timing of the molt of the throat and crown-forehead. The more specialized and differentiated were these areas into glittering crowns, frontlets and/or gorgets, the later they molted. Females of sexually dichromatic species, although lacking the glittering plumage of their males in these areas, nevertheless showed delays in head molt nearly or quite as great as those shown by males.