Apodiformes

The Apodiformes is an order, or taxonomic grouping, of birds which traditionally contained three living families—the Apodidae (swifts), the Hemiprocnidae (treeswifts), and the Trochilidae (hummingbirds); however, in the Sibley-Ahlquist taxonomy, this order is elevated to the superorder Apodimorphae, in which hummingbirds are separated into a new order, the Trochiliformes. With nearly 450 species identified to date, it is the most diverse order of birds after the Passeriformes (the "perching" birds).

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.

Aegialornis is a genus of prehistoric apodiform birds. It formed a distinct family, the Aegialornithidae, and was in some ways intermediate between modern swifts and owlet-nightjars, lacking the more extreme adaptations to an aerial lifestyle that swifts show today, but already having sickle-shaped wings like them. They do not appear to be a direct ancestor of modern swifts, however, but rather a group that retained an overall basal morphology. Altogether, they were not too dissimilar from modern treeswifts.

subspecies of bird

Eocypselus is a genus of prehistoric birds related to modern hummingbirds and swifts. Five species of Eocypselus are currently known. Compared with modern apodiforms, it may have been a better percher with shorter wing feathers, and it might have been nocturnal.