51 
moult are difficult to distinguish from the Parasitic. The best distinction seems to be in 
the colour of the shafts of the primary feathers. In this species the first two feather 
Bhafts (counting from the outside) are white, the remainder darken suddenly instead of 
gradually and progressively as on the Parasitic. This distinction may not be infallible 
and occasional juvenile specimens may occur that are very difficult of determination. 
Field Marks. For recognition as Jaegers See Family Field Marks , page 48* The 
excessive projection of middle tail feathers and their being fine and attenuated instead of 
broad and twisted probably make the best specific field marks. 
Nesting. On the ground, on the moors and tundras of the north. 
Distribution. Breeds in the arctics of Europe, Asia, and America. Probably less 
common out of the far north than either of the other two. 
Many old records of this species have proved to be Parasitics and the 
species should be identified with care. 
FAMILY — LARIDAE. GULLS AND TERNS 
General Description. The Gulls and Terns are Long-winged Swimmers, easily differ- 
entiated from the Jaegers by the shape and construction of the bill (Figure 94) which 
shows a single continuous surface without distinct parts or joints. The colours of the adult 
are usually pure white, with white or pearl-grey to black mantles, often with black wing- 
tips, hood, cape, or cheek spots. 
Distinctions. Bill with continuous surface and sharp projecting angle on lower 
mandible is sufficient to diagnose the family in all plumages. Colours are quite character- 
istic, though some species during juvenility are uniformly dark, approaching the dark 
phases of the Jaegers. 
Field Marks. Coloration and flight characteristics are the best field marks. 
Nesting. Gulls generally build on ground, on rocky ledges or flat shores, in sandy, 
grassy, or marshy places; rarely, in trees. 
Distribution. Gulls and Terns are distributed over all the world, usually near large 
bodies of water, but sometimes occurring far inland; for instance, in our prairie regions. 
Subfamily — Larinae. Gulls 
General Description. With the family description in mind the Gulls can be confused 
only with the Terns ( See page 61). 
Distinctions. May be distinguished from the Jaegers 
by the bill and coloration characters. (See previous family 
description, page 48 ); from the Terns, by their more 
robust build and mode of flight. Bills especially are heavier 
and stronger (Compare Figure 94 with 101 and 102). As a 
rule, tails are square. Distinctly forked in only one 
species, Sabine’s Gull, See page 61. Though as much 
masters of flight as the Tern they have less agility and per- 
form fewer aerial gymnastics. Young Gulls are often quite 
brownish and dark, in marked contrast with the adult. 
Young Terns are usually light in coloration. 
There are two principal distinctly characteristic types 
of adult coloration amongst our Canadian Gulls: the 
_ ? „ medium-sized Gulls, white with bluish mantle, and the 
Bonaparte’s Gull type, similar but smaller with black hood over whole head and neck. 
The species that do not fall into either of these categories are the Ivory Gull, entirely 
E ure wiiite, and Heerman’s Gull, generally grey, lighter below, and with a nearly white 
ead. 
Field Marks. Large birds of heavier flight than the Terns. Square tails; surface 
feeding habits (Gulls rarely diving from the wing); and the horizontal carriage of the 
bill when flying are the best guides by which to distinguish the Gulls from the closely allied 
Terns. 
Nesting. On rocky shores or cliffs near the water in various localities, depending 
upon the species and locality. 
Distribution. Almost cosmopolitan in range and few countries are without representa- 
tives of the subfamily. In Canada about twenty-five species are known to occur. 
91054 — 4J 
Typical bill outline of gull 
(Glaucous-winged) ; 
scale, J. 
Herrinv Gull tvno. lnro-fi nr 
