GULLS. ' 67

throat sometimes washed with the same color; under parts white; sides, lower belly, and crissum 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.—-Si1nilar in plumage to im. of S. parasiticus, but differing 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. Egg/8, two to three, similar in color to those of the preceding, 2'10 x 1'50.

FAMILY LARIDAE. GULLs AND TERNS.

This family contains about one hundred species divided equally between the subfamily Lam'me (Gulls) and subfamily Stew-Maw (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 Larinw. 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 1500.

A. Back dark slaty black. . . . . . . . 47. BLACK-BACKED GULL. B. Back pearl-gray. (1. Outer primaries marked with black. 51a. AM. HERRING GULL. 51. HERRING GULL. b. No black on primaries. b1. Bill under 2 00. b9. Primaries light pearl-gray, fading gradually into white at their tips........ ......43.I.CELANDGULL