Apodidae or swifts, is a family of highly aerial birds. They are superficially similar to swallows, but are not closely related to any of the passerine species. Swifts are placed in the order Apodiformes, which they share with hummingbirds. The treeswifts are closely related to the true swifts, but form a separate family, the Hemiprocnidae. Resemblances between swifts and swallows are due to convergent evolution, reflecting similar life styles based on catching insects in flight.