218 
CHARADRIIFORMES 
FAMILY LARIDAE. GULLS AND TEENS 
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 316), 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. Rill with continuous surface 
and sharp projecting angle on lower mandible is 
sufficient to diagnose the family in all plumages. 
Colours are quite characteristic, though some spe- 
cies during juvenility are uniformly dark, approach- 
ing the dark phases of the jaegers. 
Field Marks. Coloration and flight character- 
istics are the best field marks. 
Figure 316 
Heads of: 
a, Gull; b, Tern. 
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 234). 
Distinctions. May be distinguished from the jaegers 
by the bill and coloration characters. {See previous family 
description, page 215); from the terns, by their more robust 
build and mode of flight. Bills especially are heavier and 
stronger (Figure 317). As a rule, tails are square. Dis- 
tinctly forked in only one species, Sabine’s Gull, See page 
234. Though as much masters of flight as the tern they 
have less agility and perform 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 
Herring Gull type, large or medium-sized gulls, white with bluish mantle, and the Bona- 
parte’s Gull type, similar but smaller, with black hood over whole head and neck. Species 
that do not fall into either of these categories are the Ivory Gull, entirely pure white, 
and Heermann’s Gull, generally grey, lighter below, and with a nearly white head. 
Figure 317 
Typical bill outline of gull; 
(Glaucous- winged); 
scale, J. 
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 w r hen 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 kn own to occur. 
Though gulls are essentially sea birds they are at times found at 
considerable distances from large bodies of water and flocks often follow 
the prairie ploughman to search for insects in the newly turned furrows. 
They feed from the surface of the water, seldom diving, or glean from the 
shores, beaches, or fields. 
Economic Status. Gulls eat any form of animal matter, fish, crusta- 
ceans, molluscs, insects, offal, and — when opportunity offers — young birds 
and mice. 
