Those who would argue that the Giant Pigeon is not the most unique and bizarre Sandy Island bird are invariably arguing that the title goes to the Bare-chested Parrot. It is certainly one of only two contenders for most unique and bizarre among the parrots, the other being the Kakapo of New Zealand - to which the Bare-chested has some striking similarities. The Bare-chested is a very large parrot, smaller than some macaws but still around 25 inches in length. Though it is believed to be closest related to the lorikeets of the genus Vini, its body shape is most similar to that of an Amazon, with a relatively very short tail. The throat and chest are completely unfeathered and form a large pink patch of bare skin. The plumage is otherwise a typical parrot shade of green, with a red forehead and rump, light blue nape and dark blue vent. The bill is orange and the legs pink. The Bare-chested is the only flightless parrot besides the Kakapo, and certainly the only flightless arboreal parrot. The wings are shorter relative to the body than those of the Kakapo. One physical feature separates the Bare-chested Parrot from all other birds: its feet lack a middle toe. It grips a branch with one toe in front and two behind, though the outer (rear) toe can be swiveled outward like that of a turaco.
The Bare-chested Parrot’s two main idiosyncracies are its symbiosis with the wattle palm and its extreme behavioral sexual dimorphism. Male Bare-chested Parrots may have the smallest territories of all birds when measured in land area. They are each restricted to a single tree, as they are - like fat Giant Pigeons - flightless and walkless. They are not as inconvenienced as the pigeons, for their one method of locomotion is quite agile - branch clambering in typical feet-and-beak parrot fashion. Necessarily, as the wattle palm is their only home, male Bare-chested Parrots are especially intensely symbiotic with the palms. The flowers, buds, fruit, and seeds are their only food; they eat the fruits while they are still attached and only approaching ripeness, before they fall and are gorged on by Giant Pigeons. In one of the most unusual quirks of wattle palm biology, the seeds remain attached to the tree when the fruits fall off. There are enough seeds on one tree that the parrots cannot deplete the resource at any time; the flowers and fruits form behind the old seeds. The male parrots can squirt their droppings a remarkable distance in order to disperse the seeds. The wattle palm, which is named for the thick involucre of fronds at its crown forming a flattened, acacia- (wattle-) like shape, has evolved a built-in nest site for the parrots. The depression at the center of the involucre is a deep pit, large enough to house ten or eleven nests and protected from rain by large overhanging side-fronds. Only the males incubate; as discussed below, this species is the only polyandrous parrot (the same wags who came up with “incubus incubation” call it “polly-androus”). They have no reason to leave the nest, as the fruits are attached near the nest pit where they are easy to reach. For this reason, Robber Starlings never bother them; the parrot’s beak, adapted to cracking the large hard wattle palm seeds, is certainly strong enough to sever a starling’s neck.
The clutch size of the Bare-chested Parrot is always only one egg. The chick is fed on the larva of a beetle-mimic fly, the palm’s pollinator, which infests the overhanging fronds at exactly the time of chick-rearing. Female chicks are more precocial than males, as they have typical walking leg muscles and can walk. (Males’ leg muscles are partially atrophied as a result of their obligatory walklessness.) The females fledge when the fruits fall; these “debutantes” clamber down from the nests and live terrestrially, walking gingerly with a high-heeled gait and eating fallen wattle palm fruit with the flocks of Giant Pigeons. As the pigeons do later, the female parrots sustain themselves on other fruits and seeds once the wattle palm fruits are all devoured, though they occasionally clamber up into the wattle palms to eat buds and flowers with the males. Not long after the fallen fruits are gone, the male parrots begin their courtship. As with the Kakapo, this consists only of a vocalization; the Bare-chested’s “song” is an extremely loud, long, screechy skronk that ascends in pitch followed by a descending series of shorter, softer honks. The entire population of male Bare-chested Parrots essentially forms a small number of permanent leks based on the locations of the wattle palm groves. Each tree is literally a family tree, as its resident male parrots are always grandfathers, fathers, sons, and/or grandsons. As with other polyandrous birds, there is essentially no pair bond; females will mate with several males each year and lay eggs in many trees’ nests, including sometimes multiple nests within a tree.
The exact timeline of the Bare-chested Parrot’s life cycle has not been studied in detail yet, including the age of sexual maturity. It seems that the female’s “debutante” stage extends over several years, but this is not known for certain; the equivalent point in the male’s development appears to be a period of clambering among his palm’s fronds and working up his courtship call, resulting often in comical “sub-skronking”. The nests are obviously used for generations and as such do not need to be “built”, but at the start of the breeding season males begin to replenish them with strips torn from the overhanging fronds’ midribs. It appears that if there are more adult male parrots in a tree than the nest site capacity in the tree’s involucral pit, the older males will stop displaying and breeding to make space for new nesters.
Bare-chested Parrots seem to have a low mortality rate. Their only predator is probably the Barn Owl, which often nests in holes in wattle palm trunks and takes parrot chicks. Like other parrots, Bare-chesteds are frequently idle and playful. Young ones enjoy teasing Rainbow Lorikeets (the island’s only other parrot species) by pulling their tails.
