Wikipedia
Saw-wing
The saw-wings, Psalidoprocne, is a small genus of passerine birds in the swallow family. The common name of this group is derived from the rough outer edge of the outer primary feather on the wing, which is rough due to recurved barbs. The function of this is unknown. The birds are 11–17 cm long and black or black-and-white in colour. The genus has an African distribution and all species can be found foraging over forest and woodland.