Pygopodes—Colymbide 3 
ORDER PYGOPODES. 
This order contains diving birds, and includes the 
Grebes, Loons and Auks. The chief feature which they 
have in common is the completely posterior position 
of the legs, so that when resting on the ground the axis 
of the body is more or less vertical and the whole of 
the tarsus is often applied to the ground, while the tail 
lends additional support. 
Other external features are—nostrils never tubular 
or aborted ; wings short and rounded, never reaching 
the end of the tail, which is always short and sometimes 
absent ; tarsus compressed ; toes either webbed or lobate. 
Key OF THE FAMILIES AND GENERA. 
A. No obvious tail-feathers (Colymbide). 
a. Bill more or less slender and acute. 
ai Bill longer than the head ; tarsus, culmen and middle toe 
about equal. Echmophorus, p. 4. 
b! Bill equal to or shorter than the head ; tarsus shorter than 
the middle toe and claw. Colymbus, p. 5. 
b. Bill short, deep and strongly compressed, crossed by a black 
band. Podilymbus, p. 8. 
B. A tail of 18 to 20 short, stiff feathers (Gaviide). Gavia, p. 10. 
Family COLYMBIDA. 
Bill rather variable ; wing with twelve primaries, outer 
ones rather narrow and falcate ; tail practically absent, 
no obvious rectrices; tarsus extremely compressed, 
toes flattened and expanded into continuous lobes con- 
nected with each other at the base by an interdigital 
web; hind toe slightly elevated, lobe free from the 
other toes; claws flat and nail-like; head usually 
with crests or rufis in the breeding season; plumage 
thick and compact. 
B2 
