Ecology and evolution of the enigmatic eclectus parrot (Eclectus roratus).

Eclectus parrots (Eclectus roratus) exhibit a form of reversed sexual dichromatism (plumage coloration) not found in other birds. The females are a striking vermilion and blue, whereas the males are shiny green. Here, I summarize the major findings of a 10-year research program conducted on a wild population of eclectus parrots on Cape York Peninsula, Australia, aimed primarily at understanding the ecologic and evolutionary forces behind their unique coloration. Unlike most other parrots, eclectus parrots breed polyandrously (where multiple males mate with 1 female) and polygynandrously (where both sexes have multiple sexual partners). Their mating system appears to be driven by a shortage of nest hollows. Females with good nest sites are rare, and this forces males to share females. The red plumage of females acts as a signal of nest hollow ownership, whereas the green of males allows them to be camouflaged while foraging to feed the females and chicks. Eclectus parrots can also control the sex of their offspring, although the reasons for this are not yet clear.