Cypsiurus is a genus of swifts in the Apodidae family. These very similar species were formerly considered to be conspecific. They have mainly pale brown plumage and long swept-back wings that resemble a crescent or a boomerang. The body is slender, and the tail is long and deeply forked, although it is usually held closed. The sexes are similar, and young birds differ from adults mainly in their shorter tails. Palm swifts have very short legs which they use only for clinging to vertical surfaces, since swifts never settle voluntarily on the ground.