This much we learned in school:
Birds are highly visual animals, like humans and other apes, so their plumage color evolves because it serves as a signal to other birds, especially when choosing a mate. Plumage color and ornamentation also correspond to the birds’ mating system: long-lived monogamous birds that mate for life are often sexually monochromatic, while polygynous birds where the males do not assist in parental care are very strongly dichromatic where males have brilliant feather coloring and often have elaborate plumage adornments while the females are usually smaller and drably colored.
As opposed to humanoids of Western civilization, where the males (the breeding ones, anyway) tend toward the drab and the women well, Solomon in all his glory was not arrayed like one of these.
Not that these birds are taking after us:
Eclectus parrots (Eclectus roratus solomonensis) are medium-sized parrots that are endemic to several islands in the south Pacific Ocean, including Australia. This parrot species is famous because it has such extreme sexual dichromatism that when the birds were originally discovered by white explorers, the emerald and royal blue males and scarlet and royal blue females were thought to be different species. In fact, males were first described in 1776 while females were not described until 61 years later.
It’s not a reversal of the “traditional” sex roles, either:
Males are primarily brilliant green because they range widely in search of fresh fruits for their mates and chicks, so they face strong predation pressures, particularly from peregrine falcons, Falco peregrinus, and rufus owls, Ninox rufa. These predators, whose eyes are attuned to movement, cannot distinguish green parrots against the green foliage of flowering trees.
Meanwhile, the females have adapted to staying home:
Since there is fewer than one nest hollow per square kilometer of rainforest, female eclectus have sometimes been observed fighting to the death over this rare and precious resource. Thus, the female’s brilliant scarlet coloring serves as a warning to potential interlopers that a particular tree is occupied. Predatory birds can also see the female’s contrasting plumage, especially because she positions herself prominently on top of her nest tree, but she quickly retreats into the safety of her nest hollow when threatened.
But the housing shortage imposes its own conditions:
Limited nesting opportunities prevents this species from having either a relatively common monogamous pairing, and it also prevents a classical polyandrous mating system where the female competes for and mates with several males who have their own nests. Instead, the rarity of nest hollows caused eclectus parrots to maximize their reproductive output by evolving cooperative polyandry. This is where the female mates with two or more males and all of them remain together to raise the chicks. The resident female, who cannot leave her nest tree for fear of losing possession of it, is dependent upon being fed by a number of males.
I was originally going to work this into a “Things I Learned Today” piece, but the more I read of it, the harder it became to boil it down to a one-liner.