146 Birds of Colorado 
keeps to the heavy spruce timber most of the year. 
It is a solitary bird, never forming large flocks, though 
after the breeding season often seen in coveys or family 
parties along the mountain meadows. During the 
winter it remains in the thickest spruces, where it feeds 
on the pine needles and buds, and where its presence 
can often be detected by the debris collected undemeath. 
The iood consists chiefly of vegetable matter, about 
93 per cent. according to Judd; this is mostly made 
up of berries, especially those of the Kinnick-kinnick 
(Arctostaphylos), and of pine needles, buds and flowers ; 
the animal matter, about 7 per cent., is chiefly grass- 
hoppers, taken at high elevations in the fall or late sum- 
mer, when they are to be met with even above timber line. 
In the spring especially the male makes a curious 
booming or rumbling sound. It is said to most nearly 
resemble the sound caused by whirling a rattan cane 
round and round through the air. The production of 
this sound is connected with the two naked patches on 
each side of the neck. These are hollow vesicles in 
connexion with the air sacs, and are inflated to the 
size of half an orange at this time and are most con- 
spicuous, while at ordinary times they are concealed by 
the overlaying feathers. 
The nest, which has been described by Henshaw and 
Burnett, is placed on the ground, generally in an open 
glade, but sheltered or somewhat concealed ; that found 
by Burnett was placed in a hollow under two old logs, 
It is a simple structure of dried grass or pine needles ; 
the eggs, eight or nine in number, are whitish to buffy, 
with fine spots or dots of chocolate fairly evenly dis- 
tributed. They average 2°0 x 1°40. Fresh eggs may 
be looked for about the middle of June at the higher 
elevations, earlier at lower elevations, according to 
