THE WORLD'S BIRDS. 171 



TROPIC-BIRDS (Phaethontidcz). 



DIAGNOSIS. Long-winged sea-fowl, with long pointed 

 tails, and all the toes united by a web, and non-hooked 

 bill. 



SIZE. About that of a crow or small gull. 



FORM. Bill nearly straight, upper outline curved, 

 horny covering uniform, with distinct slit-like 

 nostrils and corner of mouth reaching below eye ; 

 feet small, with very short shanks and all toes 

 united by a web, the first very small and turned 

 inwards ; wings very long ; tail long and pointed, 

 the centre feathers especially long. Head large, 

 neck short. 



PLUMAGE AND COLOURATION. Feathering satiny, 

 colouring mostly white or very pale ; no sexual 

 difference or seasonal change. Adults with central 

 tail feathers very long ; young with the upper 

 plumage black-barred. Bill red or yellow, eyes 

 and toes dark. 



YOUNG. Helpless and fed by parents ; clothed in very 

 full fluffy white down. 



NEST. None, the birds breeding in an unlined hole in 

 a rock or tree. 



EGG. One ; white, mottled with brown. 



FOOD. Sea-fish, on which the birds swoop from the 

 air. 



GAIT. An awkward waddle ; they seldom need to 

 walk, but perch quietly when not flying ; they are 

 not often seen at rest even on the water. 



FLIGHT. With rapid continuous beats of the wings, 

 like a duck's. 



NOTE. A harsh scream or prolonged whistle. 



DISPOSITION AND HABITS. They are brave birds, 

 resenting intrusion when nesting. They are 

 usually seen well out at sea, generally singly or at 

 most in pairs, and almost always on the wing. 



