CHAPTER Ae 
COLD AND WARM WEATHER BIRDS. 
Non-divers can readily be divided into two groups, 
cold and warm weather birds, between which we find 
a wide difference in nesting, range, habitat, food and 
flight. 
Cold-weather birds arrive upon their spring migra- 
tion whilst the ground is frozen and water exists only 
in channels and running streams, solid or floating ice 
still remaining upon still-water lakes and ponds; and 
return at the fall migration, when the ice and snow 
compel them to leave their northern homes. The cold 
weather birds of our non-divers are the yellow-leg mal- 
lard, pintail or sprigtail and greenwinged teal; all of 
which conform to the above rule, with the exception 
of the pintail, which returns in the fall before the ice 
is formed. 
True cold-weather birds, as a general rule, breed 
north of latitude 45°, whereas true warm-weather birds 
breed from 25° north, and the chain is completed by 
other ducks, both divers and non-divers, which can 
be placed intermediately between them. Even fami- 
lies give the most striking contrasts, for example: The 
greenwinged teal is a true cold-weather bird, which 
breeds from latitude 45° north, whereas the bluewing 
and cinnamon teal are true warm-weather birds breed- 
ing from 25° north. A contrast is seen in the mergan- 
sers; the common merganser and red-breasted mer- 
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