The birds-of-paradise are members of the family Paradisaeidae of the order Passeriformes. The majority of species are found in eastern Indonesia, Papua New Guinea and eastern Australia. The family has 44 species in 17 genera. The members of this family are perhaps best known for the plumage of the males of the species (the majority) which are sexually dimorphic, in particular the very long elaborate feathers extending from the beak, wings, tail 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-type polygamy.
A number of species are threatened by hunting and habitat loss.
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 Semioptera, both of which are endemic to the Maluku Islands, 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 Phonygammus, 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.