DIBECTORY TO BIliDS OF EASTEIIN NORTH AMEJJIOA. 49 



a. G-ull Terns. Gelochelidon. 

 Forin, rather robust; bill, thick and somewhat gull-like- 

 fig. 58; wholly black; tail, Fig. 58. 



slightly" forked, outer feath- 

 ers, but little narrowed at 

 tip. fig. 59 ; web of toes, con- 

 siderably incised; top of 

 head, black; mantle, pearly; 

 white, beneath ; size, moderate 



1. GULL- BILLED TEKN^, G. nilotica. 

 Fi£r. 59. 



F, C, a, 1, 



14.00; head 

 and hind neck, black; 

 mantle, pale; outer 

 webs of primaries, 

 hoary ; outer tail 

 feathers are nearly 

 white; feet, black , 

 fig. 59. In w i n t e r , 

 head white more o r 

 * , C, a, 1. 1-7. less tinged on nape 



and ear coverts with dusky. Young, more or less tinged with 

 butfy above, and the top of head, hind neck, and back are 

 often streaked with dusky. Downy young, grayish-buff above 

 marked with prominent dusky spots, and with a dusky stripe 

 down either side of hind neck and upper back ; white beneath. 

 Nearly cosmopolitan ; in N. A. breeds commonly from south- 

 ern X. J. southward along the Gulf coasts ; occasionally wan- 

 dering in late summer and early autumn as far north as. 

 Mass. Flight, rather heavy and slow. 



b, Giant Terns. Thalasseus. 

 The largest of the terns, with robust form and long but 

 heavy bill which is not very sharply pointed; inner webs of 

 primaries slaty or gray; tail, much less forked than in a, fig. 

 60, but color much the same; bill, red. 



