602 Coi-ORADO College Publication 



Sialia sialis sialis. BluebiKd. 



Rare; but one record for the County, and this was for 

 many years the only record for Colorado. July 15, 1872, when 

 C. N. Holden, Jr., was visiting Aiken at the Turkey Creek 

 ranch, he took one specimen, an adult male. 



Sialia mexicana bairdi. Chestnut-backed Bluebird. 



Summer resident ; common. Arrives the middle of March, 

 leaves in October. 



While this species is common almost everywhere in migra- 

 tion, though probably never ranging quite as high as the next 

 species, it breeds mainly in the yellow pine region between 

 7,000 and 8,000 feet, where it outnumbers the Mountain Blue- 

 bird. July 17, 1899, on the Divide north of Peyton, Aiken saw 

 20 Chestnut-backed to 5 of the Mountain Bluebirds, and it is 

 probably more numerous on the Divide than anywhere else in 

 the County. The two species are sometimes found in mixed 

 flocks in the spring, especially when the weather is stormy. 

 The appearance on the plains of this Bluebird during the spring 

 migration is but for a short time, as it goes into the mountains 

 and onto the Divide by the first of April, but the storms which 

 usually come early in May drive the birds down in small flocks 

 which remain until the weather clears and the snow melts. 

 At these times the birds often become much emaciated and 

 some die from starvation, being unable to obtain food while 

 the snow is on the ground. 



Aiken found a nest on Turkey Creek, May 27, 1872, in a 

 woodpecker's hole, with young half fledged. 



Sialia currucoides. Mountain Bluebird. < 



Summer resident ; common. Arrives from the first to the 

 middle of March. The majority leave in October. 



There are various December and January records, as well 

 as February. It had just arrived at the Strickler Tunnel April 



