黑玄燕鷗 Anous minutus

A medium-sized black tern with a tail that appears square or slightly forked. Smaller and darker than Brown Noddy with a shorter tail, thinner bill, and more contrasting white cap. Uniformly black back, wings and tail, and dark legs, except on the main Hawaiian islands where tail and rump are grayish and feet and legs are bright orange. Nests on coastal cliffs, in sea caves, and in trees. More often seen in groups than Brown Noddy. Often seen from shore.