BIRDS OF COLORADO. 
55 
among the few that breed throughout their range. It has been 
taken all over Colorado, but apparently is more common as a 
breeder in the western half, not because it is more common 
there in migration, but it seems to prefer the higher altitude. 
Records of its breeding on the plains are not numerous, but in 
the mountain parks at about 8,000 feet it is one of the most 
numerous of the summer resident ducks. 
143. Dafila acuta. Pintail. 
Summer resident; rare; in migration, common; winter 
resident, rare. Some days during spring and fall migration this 
duck is very common on the plains. It is a bird of the plains, 
seldom going above 6,000 feet. A few remain around open 
water on the plains through the winter. It was recorded 
several years ago as breeding in the State (Ridgway, Bull. Es- 
sex Inst. V. 1873, 174 )? though it usually breeds from the 
northern row of states in the United States northward. Both 
W. G. Smith and G. F. Breninger write that it breeds in Lari- 
mer County, east of the foothills. 
144. Aix sponsa. Wood Duck. 
Summer resident ; rare. Occurs over all of the United 
States and breeds throughout its range, but it must be con- 
sidered as one of the rare ducks in Colorado. It has been taken 
at Loveland and is occasionally taken on the lakes near Denver. 
C. F. Morrison says, “I found this duck at Fort Lewis, where 
it no doubt breeds, although I found no nest. Abundant about 
the headwaters of the Rio La Plata at an elevation of 9,500 
feet.” (O. & O. XIII. 1888, 165.) 
146. Aythya americana. Redhead. 
Migratory; common. Breeds far north. Is more common 
in Colorado than the Canvas-back and occurs throughout the 
State. Is one of the earlier ducks to move in the spring and 
occasionally a few appear in the fall by the middle of September, 
sometime before the regular flight begins. 
147. Aythya vallisneria. Canvas-back. 
Migratory; not common. A few are observed spring and 
fall over all of the State, and sometimes quite large flocks are 
noted. It lingers late in the fall and has even been noted 
in the winter on the plains. Breeds far north. 
148. Aythya marila nearctica. American Scaup Duck. 
Migratory; rare. Occurs on both sides of the range, but 
never common anywhere. Has been seen as late as December 
in southwestern Colorado at 9,000 feet. (Drew, B. N. O. C. VI. 
1881, 85.) Breeds far north. 
