The birds-of-paradise are members of the family Paradisaeidae of the order Passeriformes. The majority of species in this family are found on the island of New Guinea and its satellites, with a few species occurring in the Moluccas and eastern Australia. The family has forty species in 13 genera. The members of this family are perhaps best known for the plumage of the males of most species, in particular highly elongated and elaborate feathers extending from the beak, wings or head. For the most part they are confined to dense rainforest habitat. The diet of all species is dominated by fruit and to a lesser extent arthropods. The birds-of-paradise have a variety of breeding systems, ranging from monogamy to lek-based polygamy.
The family is of cultural importance to the inhabitants of New Guinea. The trade in skins and feathers of the birds-of-paradise has been going on for two thousand years; and, the birds have been of considerable interest to Western collectors, ornithologists and writers as well. A number of species are threatened by hunting and habitat loss.
Description
Birds of paradise are generally crow-like in general body-form, and, indeed, are the brother group to the corvids (crows and jays). Birds-of-paradise range in size from the King Bird-of-paradise at 50 g (1.8 oz) and 15 cm (5.9 in) to the Curl-crested Manu code at 44 cm (17.3 in) and 430 g (15.2 oz). The male Black Sicklebill, with its long tail, is the longest species at 110 cm (43.3 in). In most of the males are larger and longer than the female, the differences ranging from slight to extreme. The wings are rounded and in some species structurally modified on the males in order to make sound. There is considerable variation in the family with regard to bill shape. Bills may be long and decurved, as in the sicklebills and riflebirds, or small and slim like the Astrapias. As with body size on average bill size varies with sex, although species where the females have larger bills than the male are more common, particularly in the insect eating species. For reasons of camouflage plumage of the females typically blends well with their habitat, unlike the bright attractive colors found on the males.
Plumage variation between the sexes is closely related to breeding system. The manucodes and Paradise-crow, which are socially monogamous, are sexually monomorphic. So are the two species of Paradigalla, which are polygamous. All these species have generally black plumage with varying amounts of green and blue iridescence.
Habitat and distribution
The centre of bird-of-paradise diversity is the large island of New Guinea; all but two genera are found in New Guinea. The two that are not are the monotypic genera Lycocorax and Semiptera, both of which are endemic to the Moluccas, to the west of New Guinea. Of the riflebirds in the genus Ptiloris, two are endemic to the coastal forests of eastern Australia, one occurs in both Australia and New Guinea, and one is only found in New Guinea. The only other genus to have a species outside New Guinea is Manucodia, one representative of which is found in the extreme north of Queensland. The remaining species are restricted to New Guinea and some of the surrounding islands. Many species have highly restricted ranges, particularly a number of species with restricted habitat types such as mid-montane forest (like the Black Sicklebill) or island endemics (like the Wilson's Bird-of-paradise).
The majority of birds-of-paradise live in tropical forests, including rainforest, swamps and moss forest, nearly all of them solitary tree dwellers. Several species have been recorded in coastal mangroves. The southernmost species, the Paradise Riflebird of Australia, lives in sub-tropical and temperate wet forests. As a group the manucodes are the most plastic in their habitat requirements, with in particular the Glossy-mantled Manucode inhabiting both forest and open savanna woodland. Mid-montane habitats are the most commonly occupied habitat, with thirty of the forty species occurring in the 1000–2000 m altitudinal band.
Diet and feeding
The diet of the birds-of-paradise is dominated by fruit and arthropods. The ratio of the two food types varies by species, with fruit predominating in some species, and arthropods dominating the diet in others. The ratio of the two will affect other aspects of the behaviour of the species, for example frugivorous species tend to feed in the forest canopy, whereas insectivores may feed lower down. Frugivores are more social than the insectivores, which are more solitary and territorial.
Breeding
Most species have elaborate mating rituals, with the Paradisaea species using a lek-type mating system. Others, such as the Cicinnurus and Parotia species, have highly ritualised mating dances. Males are polygamous in the sexually dimorphic species, but monogamous in at least some of the monomorphic species. Hybridisation is frequent in these birds, suggesting the polygamous species of bird of paradise are very closely related despite being in different genera. Many hybrids have been described as new species, and doubt remains regarding whether some forms, such as Rothschild's Lobe-billed Bird of Paradise, are valid. Despite the presence of hybrids, some ornithologists hypothesise that at least some putative hybrids are valid species that may be extinct.
Birds-of-paradise build their nests from soft materials, such as leaves, ferns, and vine tendrils, typically placed in a tree fork. Clutch size is somewhat uncertain. In the large species, it is almost always just one egg. Smaller species may produce clutches of 2–3. Eggs hatch after 16–22 days, and the young leave the nest at between 16 and 30 days of age.
Taxonomy and systematics
For many years the birds-of-paradise were treated as being closely related to the bowerbirds. Today while both are treated as being part of the Australasian lineage Corvida, the two are now only thought to be distantly related. The closest evolutionary relatives of the birds-of-paradise are the crow and jay family Corvidae, the monarch flycatchers Monarchidae and the Australian mudnesters Struthideidae.
A 2009 study examining the mitochondrial DNA of all species to examine the relationships within the family and to its nearest relatives estimated that the family emerged 24 million years ago, older than previous estimates. The study identified five clades within the family, and placed the split between the first clade, which contains the monogamous manucodes and Paradise-crow, and all the other birds-of-paradise, to be 10 million years ago. The second clade includes the parotias and the King of Saxony Bird-of-paradise. The third clade provisionally contains a number of genera, Seleucidis, the Drepanornis sicklebills, Semioptera, Ptiloris and Lophorina, but support values for some of these is inclusions is low. The fourth clade includes the Epimachus sicklebills, Paradigalla and the astrapias. The final clade includes the Cicinnurus and the Paradisaea birds-of-paradise.
