GULLS. 67 



throat sometimes washed with the same color; under parts white; sides, 

 lower belly, and orissum slaty fuscous ; central tail-feathers extending about 

 7'00 beyond the others, the projecting ends narrow and pointed. (No dark 

 phase of this species has been described.) Im. — Similar in plumage to im. 

 of S. parasiticus, but dift'ering otherwise as pointed out under that species. 

 L., 21-00 ; W., 12-50 ; T., Ad., 12-00, Im., 5-50 ; B., 1-08. 



Range. — Northern part of the northern hemisphere; in America nests 

 in Greenland and quite abundantly " along the Anderson, in the ' Barrens,' 

 and also on the arctic coast" (Macfarlane); migrates southward along the 

 coasts, and rarely through the Great Lakes, to the Gulf of Mexico and West 

 Indies. 



Nest, a slight depression in the ground, sometimes scantily lined with 

 grasses. Hggs, two to three, similar in color to those of the preceding, 

 2-10 X 1-50. 



Family Larid^. Gulls and Terns. 



This family contains about one hundred species divided equally 

 between the subfamily LarincB (Gulls) and subfamily Sternince (Terns). 

 They are distributed throughout the world. Some forty species in- 

 habit North America. With few exceptions they agree in possessing 

 the marked characters of their respective subfamilies, under which 

 they may be more conveniently treated. 



Subfamily LarincB. Gulls. 



Generally speaking, Gulls are maritime and pelagic, though some 

 species are found inland. As compared with Terns, Gulls are less 

 graceful and active on the wing. In flight the bill points forward in 

 the plane of the body, not downward toward the earth, as in the Terns. 

 They procure their food largely by picking it from the surface of the 

 water or land with their strongly hooked bills, not by plunging or 

 darting, as do the Terns. Some of the species are true birds of prey, 

 and feed on small mammals and the eggs and young of other birds. 

 Gulls are better swimmers than Terns, and pass much time resting on 

 the water. They nest in colonies, generally on the ground, sometimes 

 on rocky ledges, and rarely in trees. 



KEY TO THE SPECIES. 



I. Wing over 15-00. 



A. Back dark slaty black 47. Black-backed Gcll. 



B. Back pearl-gray. 



u. Outer primaries marked with black. 



51a. Am. Heehing Gull. 51. Heeeing Gull. 

 J. No black on primaries. 

 ii. Bill under 2-00. 

 f. Primaries light pearl-gray, fading gradually into white at their 

 tips 43. Iceland Gull. 



