Hemiprocnidae

Treeswifts or crested swifts are a family, the Hemiprocnidae, of aerial birds, closely related to the true swifts. The family contains a single genus, Hemiprocne, with four species. They are distributed from India and Southeast Asia through Indonesia to New Guinea and the Solomon Islands.

Treeswifts are small to medium-sized swifts, ranging in length from 15 to 30 cm. They have long wings, with most of the length coming from the length of the primaries; their arms are actually quite short. They visibly differ from the other swifts in matters of plumage, which is softer, and they have crests or other facial ornaments, and long, forked tails. Anatomically they are separated from the true swifts by skeletal details in the cranium and palate, the anatomy of the tarsus, and a nonreversible hind toe that is used for perching on branches (an activity in which true swifts are unable to engage). The males have iridescent mantle plumage. They also have diastataxic wings, that is they lack a fifth secondary feather unlike swifts in the Apodini, which are eutaxic. thumb|left|Moustached treeswift on its nest. Biak, [[New Guinea.]]