Drew on Birds of San Juan County. Colorado. 85 



FIELD NOTES ON THE BIRDS OF SAN JUAN 

 COUNTY, COLORADO. 



BY FRANK M. DREW. 



In the southwestern portion of Colorado, and lying wholly 

 within the Rio Colorado basin, is the little county of San Juan. 

 With the exception of Baker's Park and tributary gulches. San Juan 

 is composed of mountain peaks, fully one-third of the county being 

 above timber-line. (For a good description of the Park and ad- 

 jacent country, see F. B. Rhoda's account in Hayden's Report for 

 1S74.) The average elevation of the Park is 9,500 feet; the low- 

 est part of the county is at the extreme southern end, in the 

 Animas Canon. Here it is about S.500 feet, and for a short dis- 

 tance up this narrow gorge runs a tongue of vegetation entirely 

 different from the characteristic flora of San Juan. This different 

 growth is composed of pines, poplars, and scrub oak and maple 

 bushes. The flora of the county is essentially western and boreal. 



The peaks are the homes of such sub-arctic mammals as La- 

 gomys prfnceps, Arctomys fiavivcuter. Leftus americanus 

 bairdi, all in great abundance, as well as Erethizon epixanthus, 

 Ov/'s montana, Fclis concolor, Neotoma cinerea, and others. 

 But one reptile — a snake — was seen ; neither batrachians nor 

 fishes were found. Owing to the peculiar topographical position 

 of the county, the list becomes of a little more interest than a 

 mere faunal paper, as it is composed of those birds which range 

 to, or above 10.000 feet. My observations extend from June, 1S79 

 to January. 1SS1. The nomenclature is. in the main, that of 

 Dr. Coues ; that is. in so far as I have been able to keep up with 

 recent revisions. 



1. Turdus migratorius propinquus. Ridg. Western" Robin. — 

 Very common ; breeds, the nest being' placed indifferently two feet from 

 the ground in bushes, or twenty-five feet up in trees. One nest which I 

 found was curiously placed in some willow bushes in much the same man- 

 ner as the nest of a Red-winged Blackbird, being supported entirely by 

 the sides. How the bird made a start is a puzzle to me. If climatic 

 changes have caused such a marked hoariness — a bleached color — in 

 Partis atricapillns septentrional is. why has climatic variation bleached 

 the -white out of the robin's tail and left it nearly or quite black? The 

 birds are found here from April until the last of November and occasion- 

 ally rear two broods. 



