LOONS 
37 
DESCRIPTIVE ORNITHOLOGY 
CLASS— AVES. BIRDS 
Birds, as a class, may be divided into toothed and toothless birds, 
although the former are now extinct and are known only by their frag- 
mentary remains preserved as fossils. All modern birds are toothless. 
Some species, for example the Mergansers, are furnished with serrations 
in the horny bill that have a superficial resemblance to teeth (Figure 8, 
page 25), but examination shows that they are not true teeth. 
All Canadian birds have deep keels to their sterna for the purpose of 
anchoring the powerful flight muscles. They so differ from the struthious 
or ostrich-like birds which have flat breast bones. They, therefore, fall 
into the 
SUPERORDER— NEOGNATHAE, NON-STRUTHIOUS BIRDS 
Of these keel-breasted birds we have several orders, of which the first is: 
Order — Gaviiformes. Loons 
FAMILY — GAVIIDAE. LOONS 
General Description. The loons are large divers, with straight, sharply pointed bills 
and with the feet fully webbed (Figure 2, page 24). In the adult state they are coloured 
in strikingly contrasting patterns, mostly black and white. 
Distinctions. Larger than ducks and with shorter necks than geese. These features 
and the sharp, pointed bill are diagnostic. Tails more evident than in the grebes. 
Field Marks. Size, length of neck, and bill. In flight, the feet are trailed behind the 
tail. 
Nesting. On low shores, in the immediate vicinity of water where they can dive 
almost directly from the nest. 
The loons are probably even better divers than the grebes, but they 
rise less easily from the water, and unless there is a good breeze that they can 
face, require a long, splashing start over the surface before becoming 
wing-borne. 
Economic Status. Their food is composed almost entirely of fish, but 
owing to the small number of loons usual in any one locality their direct 
economic importance is small. 
Figure 72 
Bill outline of Common Loon; scale, \. 
7. Common Loon. loon, great northern diver. le heart commun (Le 
Grand Plongeon). Gavia immer. L, 32. Plate I A. 
Distinctions. The summer adult Common Loon is easily distinguished from any 
of the other loons, except the Yellow- billed, by its marked coloration, but young birds 
may be more difficult to differentiate. From the Yellow-billed, which is but slightly 
