The distinctive wing shape arises from the large size of the 'hand' and the fact that P8 and P9 are longer than P7 or P10.
All species are highly pelagic and poorly known at sea.
The identification of several species is fairly difficult at sea and this hampers a full understanding of their marine distribution. On land, crouch on bent legs and move with shuffling gait. In the air, the flight is erratic with swoops, bounces, flutters and skimming motions. Depending on species, may be solitary or gregarious at sea. Churring calls are a notable feature of breeding colonies.