BIRDS OF COLORADO. 
II4 
Osburn and Smith, and there are both male and female in the 
Maxwell Collection. Passes through Colorado the latter half 
of May. 
648. Compsothlypis americana. Parula Warbler. 
Summer resident; rare. An eastern species coming 
scarcely west to the foothills of the Rocky Mountains. Has 
never been taken in the northern part of Colorado, but from 
Colorado Springs south and southeast a few occur each summer. 
Arrives early iii May. 
652. Dendroica aestiva. Yellow Warbler. 
Summer resident; abundant. The commonest Warbler 
that breeds on the plains. Arrives the first week in May and 
breeds both on the plains and in the mountains to 8,000 feet, 
though rather more common at the lower altitudes. 
652a. Dendroica aestiva sonorana. Sonora Yellow War- 
bler. 
Summer resident; probably common. To the southwest- 
ward the eastern form of the Yellow Warbler shades into the 
Sonora variety. It is not yet known with definiteness, where 
the dividing line should be drawn. In his original description 
of sonorana^ Mr. Brewster says that a Colorado specimen is a 
fair intermediate between sonorana and niorcomi. (Auk, V. 
1888, 139.) A specimen taken by Capt. P. M. Thorne at Fort 
Lyon, Mr. Brewster marks as not typical but nearest sonorarta. 
If this view is finally adopted, it will probably include under 
sonorana many of the Yellow Warblers of southern and especi- 
ally southwestern Colorado. 
654. Dendroica caerulescens. Black-throated Blue War- 
bler. 
Migratory; rare. The only Colorado record is that of a 
specimen taken in the vicinity of Denver by Mr. H. G. Smith, 
May 24, 1888. (Nidologist, III. 1896-7, 76.) In the Auk, XI. 
1894, 182, the present writer recorded a specimen at Colorado 
Springs that he was assured had been shot in that vicinity. 
Further investigation has shown that the bird came from with- 
out the State. 
655. Dendroica coronata. Myrtle Warbler. 
. Migratory; not uncommon. Arrives the last of April or 
early in May and is not uncommon for two or three weeks along 
the base of the foothills and on the plains. Migrates from ten 
days to two weeks ahead of auduhoni^ but in May the two species 
are often found together. A few go into the foothills to 9,000 feet. 
Scarcely known west of the Rocky Mountains. The last leave 
