Meeting Abstract
A major source of variation in the animal kingdom stems from differences between the sexes. This concept, sexual dimorphism, is typically studied across species with a phylogenetic approach, but can also be studied within species if variation in dimorphism exists (i.e. when one sex varies in similarity to the other). Though frequently found in males, this type of variation is relatively rare in females. Female-limited polychromatism is an evolutionary conundrum because theories typically used to explain ornamentation (e.g. sexual selection) do not readily explain the observed variation in females. Many hummingbird species contain female-limited polymorphism. In one, Florisuga mellivora, ~30% of females captured had ornamented plumage nearly identical to that of the male, while the others had drab coloration. The contexts in which male-like coloration in females might have evolved have not been previously studied, but sexual or territorial harassment have been hypothesized. We observed interactions of wild hummingbirds with taxidermy mounts of male-like females, drab females, and true males at feeders. Male F. mellivora attempted copulations with drab females more often than with male-like females. However, territorial attacks were also more often directed toward drab females than both male-like females and true males. Territorial behavior toward drab female mounts was more frequent than sexual behavior, and sexual behavior in the wild was seen much less often than territorial behavior toward females. Therefore, both sexual and territorial contexts could be relevant, but territorial harassment may be a more important context for the evolution of male-like coloration in female hummingbirds.
