White-necked Jacobin (Florisuga mellivora mellivora) female
23 January 2009, Rancho Naturalista, Costa Rica
This is a female with an interesting patchwork of blue and green plumage.
Females of this species are highly variable with some individuals almost
indistinguishable from adult males. Females average slightly smaller than
males and have slightly longer bills.
We usually think of the brightly colored male plumage as derived, having
evolved through sexual selection in which males compete for females by
showing off. However, in hummingbirds, it seems the bright male-like
plumage may be the ancestral state and the duller female plumage derived
from it as a predator avoidance adaptation.
Evidence for this comes from the Lesser Antilles where bird-eating raptors
are rare or absent. There hummingbirds tend to be monomorphic with females
similar to or indistinguishable from the glittering males.
Panasonic Lumix LZ5 / Nikon FieldScope 3 / 30X WA hand-held (no adapter)