Frequently encountered near the shores of tropic seas are the frigate-birds (family Fregatidae) which are recognisable in flight by their remarkably long wings (in some species the wingspan measures over 7.5 feet) and long, deeply forked tails. The long slender bill is sharply hooked at the tip. The males have brightly coloured throat pouches. Thought all four toes are webbed they are not used for swimming, and the birds spend most of the time in the air. Their adroitness in flight provides them with two methods of procuring food - catching it from the surface of the sea or pirating it from gulls, cormorants or pelicans by harassing them till they disgorge their prey, which the frigate-bird catches in mid-air as it falls. Frigate-birds nest colonially on trees, shrubs, and rocks, feeding the single white-headed offspring from beak to beak.

Great frigate-bird, Fregata minor, is marked by a yellow-brown band across the wings, otherwise it is coloured black; the female has a white throat and breast. It inhabits the tropic zone of the Pacific, Atlantic and Indian Oceans. A very similar bird, the magnificent frigate-bird, Fregata magnificens, occurs along the coasts of tropical America and in the South Atlantic. It is quite common in summer in southern Florida, though it does not nest there, and is also occasionally seen on the Gulf and west coasts of the United States during storms.