520 Birds of Colorado 
In Colorado the Olive-backed Thrush is a common spring and fall 
migrant, both in the plains and mountains ; it arrives from the south 
early in May, 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 earlier 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); Salida, 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 Ist, 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 lined 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 limb. 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. 
