114 BIRDS OF COLORADO. 



Osburn and Smith, and there are both male and female in the 

 Maxwell Collection. Passes through Colorado the latter half 

 of May. 



648. Compsothfypis 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 in 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. 



653a. 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 morcomi. (Auk, V. 

 1888, 139.) A specimen taken by Capt. P. M. Thorne at Fort 

 Lyon, Mr. Brewster marks as not typical but nearest sonorana. 

 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 caeruiescens. 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 auduboni, 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 



