Male Eclectus Offer Support
Each female is attended by up to five dutiful males that scour the countryside for fruit. Upon returning, they lock beaks with the female and regurgitate the fruit pulp and seeds. With great effort we managed to catch some males in mist nets that were hoisted into the rainforest canopy and attached tiny radio-transmitters to their tail feathers before letting them go. This proved to be a wonderful method from the birds’ perspective, because the attachment to the tail guaranteed that the transmitters would eventually fall off when the feather molted.
The only way to follow the birds over the rugged rainforest terrain was by mounting our aerials on a light aircraft and radio-tracking them from the air. We found that males travel up to 20 kilometers on each trip to find food and have very large home ranges of up to 100-square kilometers. They clearly work extremely hard but are rewarded with sexual favors if they feed the females well enough.
Our genetic studies using the birds’ DNA showed that males are not related to each other. They jostle, peck and claw one another for access to their shared bride. They can’t all be fathers, because she only lays two eggs at a time. However, our genetic studies have shown that many of them do eventually become fathers, at least once, if they stay with her for long enough. This can happen if the female lays a second clutch in the same season, or over multiple years. One male we studied fathered two chicks with the same female seven years apart but failed to gain any offspring with her in between!
Flirtatious Males & Partner Swapping
The males outnumber the females by about two to one, and many miss out on fatherhood despite their hard work feeding the chicks. To increase their chances, they often “two-time” their partners and visit more than one female. We saw some of the males flirt with up to five different nesting females!
They would typically alight near the nest hollow and chirp and chatter to the female. Sometimes they were chased away, but on other occasions they succeeded in mating with her. This mating system, in which both sexes seek multiple sexual partners, is unlike that of any other parrot. Males and females in most parrot species live in relatively dull and monogamous (but harmonious) marital bliss. The strange system in Eclectus parrots seems to be due to the all important shortage of nest hollows that forces males to wife-share and to look elsewhere for sex when it is not forthcoming.
The Reason Behind The Dimorphism
Ultimately, the shortage of hollows also drives the remarkable reversed color scheme of male and female Eclectus parrots. We used a technique known as spectrometry to work out the purpose of such different plumage. This entailed catching the birds, scanning their plumage and measuring the surrounding light in the rainforest using a spectrometer connected to a laptop computer. All hollows are in bright light, and females usually sit at the entrance with their heads and chests glowing like beacons. Their bright red color acts as an obvious signal to other females, saying in effect “This hollow is occupied.”
Such a strong proclamation seems essential in the females’ competitive world, but it comes at a high price. Old females with good hollows can use them to hide from predators, but young females without hollows don’t have the option of “switching off” their signal, and are twice as likely to be attacked by Peregrine falcons and Rufous owls.
Why then is male Eclectus color so different from that of the females? If we remember that females stay at their hollow and the males go out to forage, it begins to make sense. The males spend virtually all of their time in the tree-tops and, unlike the females, need to blend in with their green surroundings for safety from their aerial predators. However they also need to be bright and showy when they compete for the female’s attention at the nest hollow. To achieve this double-act, their green has an extra quality. It positively glows using a color, ultra-violet, that the parrots can see, but their predators (including humans) cannot.
Males look dull green and camouflaged to hawks and owls (and us) when they are out collecting food, but stunningly gorgeous to the other Eclectus parrots back at the nest hollow. It was only by using a spectrometer that we could detect this hidden color.
The female’s red when contrasted with the shiny green of the males as she slips out of the nest to receive food is one of nature’s truly beautiful sights. Although it took 10 years of grueling field work to get as far as we have in solving Hamilton’s mystery, the rewards of finding each piece of the puzzle have made all the effort incredibly worthwhile. The name Eclectus (with the same Greek origin as “eclectic”) is indeed apt as the ecology; the color and sexual behavior of males and females have turned out to be truly remarkable for their oddity and variety.