GULLS 153 
eed upon the eggs and young of the other birds among which they nest, 
‘arely, however, preying on their own species. 
Gulls are buoyant swimmers, and, unlike Terns, rest and roost on 
he water, often gathering in close-massed “‘beds.”’ They nest in colonies 
mn islands. The young are born covered with down of mottled pattern, 
ind though they may leave the nest in their natal dress, are dependent 
yn their parents until they acquire the power of flight. The voices 
vf Gulls possess a certain, indescribable human quality which adds 
n no small degree to the impression created when storms rule and 
hese wild cries are heard above the tumult of wind and wave. 
KEY TO THE SPECIES 
I. Wing over 15°00. 
1. Back dark slaty black. .......... 47. BuACK-BACKED GULL. 
2. Back not dark slaty black. 
A. Back pearl-gray. 
a. Outer primaries marked with black . . 51. Herring Guin. 
b. No black on primaries. 
bl. Bill under 2°00. 
b*, Primaries light pearl-gray, fading gradually into white at 
thE OS we kh Ae ee eH 43. IckELAND GULL, 
b’ Primaries pearl gray, tipped with white, and with well-de- 
fined gray spaces on the outer webs of the outer two 
primaries and on both webs of the third and fourth 
primaries. 66 6 2 ke ee ee 45. KuMmurENn’s GULL. 
el. Bill over 2:00 .........-205 42. Guaucous GULL. 
B. Back grayish, whitish, or brownish, or mottled or spotted with 
grayish or brownish. 
a. Tail black or blackish, with or without irregular white markings. 
a, Wing over 17°50; depth of ber a nostril over '70. 
Buacxk-BackED GuLu (Im.). 
a?, Wing under 17°50; depth of bul at nostril under ‘70. 
51. Herring Guy (Im.). 
b. Tail white or whitish or grayish brown, with or without black 
markings. 
bt. Bill under 2700 ........... 43. IceLAND Gutt (Im.). 
b?. Bill over 2°00. ........2.. 42, Guavucous Gut (Im.). 
[I. Wing under 15°00. 
1. Tail white. 
A. Head and throat slaty black. 
a, Outer primary black or mostly black. 
a, Outer primary entirely black ..... 58. LauGcHING GULL. 
a. Inner half of inner web of first primary white. 
62. SaBINn’s GULL. 
b. Outer primary mostly white. 
b!. Tip of first primary white. ...... 59: FRANKLIN’s GULL, 
b. Tip of first primary black. ..... 60. BonaraRTE’s GULL. 
B. Head white, sometimes washed with pearl-gray. 
a, Wings white... .- + eee eee -... 39. Ivory GuLu. - 
“Bt Wing over 11°00. 
b?, Hind-toe very small, without a mails 40. Kirtrwaks. 
63, Hind-toe normal, with a nail . 54, Rine-BILLED Gui. 
ct. Wing under 11°00 ..... ..-- . 61. Ross’s Guu 
