II2 
BIRDS OF COLORADO. 
621. Lanius borealis. Northern Shrike. 
Winter resident; common. Breeds north of the United 
States and comes south to Colorado in October. Makes its first 
appearance high up on the mountains above timber-line and 
later descends to the plains. Quite common at the western edge 
of the plains where food, in the shape of Shore Larks, is abund- 
ant. Also winters less commonly in the mountain parks to 
9,500 feet. Departs northward in March. 
622a. Lanius I udovicia n us excu bitorides. White- 
RUMPED Shrike. 
Summer resident ; common. Arrives from the south soon 
after the Northern Shrike leaves, early in April, and is quite 
common through the summer on the plains. Less common in 
the mountains to about 9,500 feet. On the plains breeds late’ 
in May and sometimes raises two broods. 
624. Vireo olivaceus. Red-eyed Vireo. 
Summer resident; rare. An eastern species coming only 
west to the base of the foothills. Allen took it in the mountains 
at 11,000 feet, but this must be considered as an accidental oc- 
currence. Arrives late in May and leaves in September. 
Capt. P. M. Thorue took it at three different times at Fort Lyon, 
where he marks it as tolerably common. Prof. Wm. Osburn 
saw but one at Loveland in several years of active collecting. 
There are both male and female in the Maxwell Collection. 
627. Vireo gilvus. Warbling Vireo. 
Summer resident; common. The most common Vireo in 
Colorado. Arrives on the plains the first week in May and at 
its upper range in the mountains by the last of the month. 
Breeds sparingly on the plains and abundantly in the mountains; 
almost as common at 10,000 feet in summer as lower down. 
Breeds about the first of July. 
629a. Vireo solitarius cassinii. Cassin’s Vireo. 
Rare or accidental summer visitant; not known to breed. 
A southwestern species not regularly reaching north to Colorado. 
There was a specimen in the Maxwell Collection that may or 
may not have been taken in this State. Mr. H. G. Smith took 
one near Denver May 13, 1888, and the specimen was identified 
by Ridgway. (Nidologist, III. 1896-7, 76.) 
629b. Vireo solitarius plumbeus. Plumbeous Vireo. 
Summer resident; common. Extends east at least to the 
base of the mountains and a few miles out on the plains. 
Arrives early in May. Breeds in the foothills and among the 
mountains to rather over 9,000 feet. Nests among the pines, 
but in migration occurs everywhere. 
