520 Birds of Colorado 



In Colorado the Olive-backed Thrush ia a common spring and fall 

 migrant, both in the plains and mountains ; it arrives from the south 

 early in ^lay, the males appearing at least a week or a fortnight before 

 the females ; most of the birds pass on further north, but a small pro- 

 portion stay with us to breed in the mountains, at from about 8,000 

 to 10,000 feet. 



Gale is the only observer who has actually taken the nest of this 

 species in Colorado, but Minot observed the bird between 9,500 and 

 10,500 feet on Pikes Peak, in June, where it was doubtless breeding ; 

 on spring migration it is common on the plains from Colorado Springs 

 to Limon, and a large series in the Aiken collection show very clearly 

 the earUer arrival of the males, the dates of these running from May 

 5th to May 27th, while the females date from May 23rd to June 6th. 

 Other migration records are : Springfield, Baca co., May 16th, males ; 

 May 29th, females (Warren) ; Fort Lyon, May 6th (Cooke) ; Pueblo, 

 May 13th-20th (Beckham) ; SaUda, May 10th (Frey) ; Denver, May 

 10th to 17th (Henshaw). 



The only record of its occurrence on the western slope of the Con- 

 tinental Divide is that of Rockwell, who found a deserted nest with 

 two eggs, on August 1st, 1905, in Mesa co., at an altitude of about 

 6,500 feet. 



Habits. — ^The Olive-backed Thrush is in no way 

 remarkable in this respect ; it is chiefly met with in 

 shrubbery and in cotton-wood groves along the valleys 

 of streams, and obtains its food on the ground, scratching 

 among dead leaves. During migration it is silent and 

 retiring, but when nesting it has a loud, ringing and 

 characteristic song, generally heard in the twilight. 



Gale found the nest of this bird on several occasions ; 

 it was placed in a willow bush close to, and almost over- 

 hanging a creek, and was securely and compactly built, 

 chiefly of grasses with fibre and leaves, and hned with 

 finer materials of the same kind ; it was attached by the 

 side or rim to several twigs, so that it was semi-pensile 

 and not saddled on the Umb. The eggs, generally four 

 in number, were blueish-green, speckled with soft rufous 

 or tan, and measured '90 x "64. Unincubated eggs 

 were met with between June 20th and July 7th. 



