Birds
Bird-of-paradise
Paradisaeidae · also called birds-of-paradise
A bird-of-paradise is what happens when female choice is left to run for millions of years with nothing to check it. In most species the female nests and raises the chicks entirely alone, so all a male offers is a performance — and the performances have escalated into capes that become bouncing smiley faces, feathers half a metre long tipped with enamel-blue flags, and forest-floor ballets on a stage swept clean of every leaf.
Overview
Birds-of-paradise are the family Paradisaeidae, about 45 species, almost all on New Guinea and its satellite islands, with a few in the Moluccas and two in northeastern Australia. They live in lowland to high-mountain rainforest and eat mostly fruit — figs and oily nutmeg-type fruits — plus insects, spiders, and small vertebrates.
Extreme sexual selection
Because the female alone raises the young, a male contributes only genes, and generations of female preference have produced iridescent colours, wire and ribbon feathers, breast shields, and dances seen in no other birds. The superb bird-of-paradise turns its cape into a bouncing “smiley face”; the parotias dance a ballerina routine; the King of Saxony waves two 50 cm head plumes. Males display at leks or on painstakingly cleared forest-floor courts, and a young male takes 5 to 7 years to grow full plumage, looking female until then. Wild hybrids between species are common.
Status
Most species are Least Concern in intact forest, but the trend is decreasing, with Wahnes’s parotia and the black sicklebill Vulnerable. The pressures are rainforest clearing for oil palm, mining, and farming, plus hunting. In the late 1800s and early 1900s tens of thousands of skins a year were exported for women’s hats, until import bans in the 1920s ended the trade.
Bird-of-paradise: common questions
Why are birds-of-paradise so ornate?
Because of an unusually pure form of sexual selection. In most bird-of-paradise species the female does all the work of nesting and chick-rearing on her own, so when she chooses a mate she is choosing only his genes and the quality of his display, with no help to gain. That frees female preference to run in whatever direction it happens to favour, and over many generations it has favoured brighter colours, stranger feathers, and more complex dances, with each small step making the males a little more extreme. The birds also live in rich rainforest with a reliable fruit supply and few predators at the display sites, which gives males the time and energy to invest in ornaments and performance rather than survival and parenting.
How many kinds of bird-of-paradise are there?
About 45 species in the family Paradisaeidae, though the exact number shifts as genetic studies split or lump populations. They range from crow-sized sicklebills and the large Paradisaea plume-birds to tiny species like the king bird-of-paradise. They are concentrated on New Guinea, which has the great majority, with a handful in the Moluccas and two, the paradise riflebird and the magnificent riflebird, reaching the rainforests of northeastern Australia. Several familiar garden and cut-flower plants are also called bird of paradise, but those are unrelated tropical plants named for a fancied resemblance to the bird.
Do female birds-of-paradise look different from males?
In most species, dramatically so. Females are typically brown, grey, or barred, well camouflaged for sitting on an exposed nest, and lack all the plumes, colour, and ornaments of the male. Young males look like females for their first several years while their adult plumage slowly develops. A few species, mainly the manucodes and paradise-crows, are exceptions in which the sexes look alike, are dull-coloured, and form pair bonds with shared parental care, and it is thought these represent the ancestral condition before extreme sexual selection took hold in the rest of the family.
Were birds-of-paradise really hunted for hats?
Yes, on a large scale. From the 1880s to the 1910s the international millinery trade consumed enormous numbers of wild bird skins for hat decoration, and bird-of-paradise plumes were among the most prized, with figures of 30,000 to 80,000 skins a year shipped out of New Guinea at the peak. The trade caused steep local declines and prompted some of the first international wildlife-protection campaigns and laws, and it was effectively ended by import bans in Britain and the United States in the 1920s. Today the birds are legally protected, populations have largely recovered where forest remains, and only limited customary use of feathers in traditional dress by New Guinean communities is allowed.