42 THE BIRDS OF MAINE 



Family LARID.^. Gulls and Terns. 

 Subfamily LARIN.E. Gulls. 



Key to the species of LARIN^E. 



A. Hind toe without a nail, a mere rudimentary knob. Kittiwake. 



B. Hind toe with nail, small but well developed. 



1. Tail forked. Sabine's Gull. 



2. Tail not forked, even. 



* Wing over 15.00 inches long, 

 a'. Back slaty black. Black-backed Gull, 

 a*. Back not slaty black, 

 b'. Back pearl gray. 



r. Bill over 1.95 along culnien. 

 ?. Outer primaries with some black markings. Herring Gull. 

 ??. Outer primaries not black marked. Glaucous Gull, 

 rr. Bill under 1.95 along culmen. 



?. Primaries uniform pale pearl gray, fading gradually 



into white at the tips. Iceland Gull. 

 ??. Primaries distinctly and sharply white tipped, with 

 darker subterminal spaces, pearl gray otherwise. 

 Kumlien's Gull. (Hypothetical List.) 

 b*. Back not pearl gray, but grayish, whitish, brownish, or 

 mottled with grayish or brownish, 

 r. Bill under 1.95 along culmen. Iceland Gull. (Im.) 

 rr. Bill over 1.95 along culmen. 



?. Tail white to grayish brown, sometimes with black 

 markings. Glaucous Gull. (Im.) 

 71. Tail black or very dark, sometimes marked with white. 

 1. Wing over 17.50 ; bill at nostril over 0.70 in depth. 



Black-backed Gull. (Im.) 

 11. Wing under 17.50 ; bill at nostril under 0.70 in depth. 

 Herring Gull. (Im.) 

 ** Wing under 15.00 inches long, 

 a'. Tail white, unmarked, 

 b'. Head and throat black. 



r. Outer primary entirely black. Laughing Gull, 

 rr. Outer primary chiefly white, sometimes dark banded or 

 marked ; always black tipped. Bonaparte's Gull, 

 b*. Head white or pearl gray. 

 r. Primaries pure white. Ivory Gull. (Hypothetical List.) 

 rr. Primaries more or less black-marked. Ring-billed Gull, 

 a*. Tail marked with black. 

 b'. Tarsus under 1.50 Bonaparte's Gull. (Im.) 



