626 U.S. NATIONAL MUSEUM BULLETIN 237 paet 2 



Incubation. — Only the female incubates. Every few hours she 

 leaves the nest to feed under the watchful eye of the male, solicitous 

 as usual. A sure sign of incubation is the singing of the male past 

 the normal short period at dawn. He sings loudly and constantly 

 from a conspicuous perch in a tree almost all the time she is incubating; 

 he stops singing and joins her the moment she leaves the nest to feed. 

 No accurate data are available on the length of the incubation period 

 in this race. 



Young. — Upon leaving the nest, the young climb up into the bushes 

 or low trees and remain stationary for long periods while uttering a high, 

 thin sip food call. The parents use the same note, but much louder 

 and more piercing, as an alarm note; when uttered it silences the food- 

 calls of the young. Only when much older do the young begin to move 

 after the parents to be fed. Then their note has filled out to the 

 ordinary locative see. 



Groups of canyon towhees seen in some autumns may be families of 

 young still staying near their parents. Thus in mid-November 

 Marshall saw two birds with a color-banded adult female in an area 

 where canyon towhees are rather uncommon. They may have been 

 her young, as they were all feeding together at a feeding station about 

 10 yards from a bush in which she had nested the previous spring. 

 A. R. Phillips writes that his latest record of a "flock" (family?) of 

 three or foiu- birds was on Feb. 19, 1939. 



Plumages. — The natal down is brown. At the time of leaving the 

 nest the fully-feathered juvenile has a bobbed tail and is in a lacy 

 brown coat with spotting on the chest, somewhat like that of a thrush. 

 During October the post-juvenal molt is completed. This replaces 

 the thin lacy body and head feathers with firmer, more solidly colored 

 feathers like those of the adult. However, the nestling wing and all 

 or most of the tail feathers are retained. A year later, in fall, a com- 

 plete molt renews the adult body plumage and at last endows the now 

 mature bird with adult wing and tail feathers. These have perfect 

 margins and are broader, blacker, and more square-ended than are the 

 corresponding juvenal feathers of fall immature birds. Therefore, the 

 bird bander can easily tell the sex and age of his captured birds by 

 these plumage criteria (for age) and measurements of the wing and 

 tail (for sex) as set forth and explained in detail in John Davis's (1951) 

 monograph of the brown towhees. 



Food. — All the feeding is done on the ground, where seeds in winter 

 and insects in summer are picked up in the bill by repeated dabs 

 while the body is held horizontal. Birds often scratch the ground by 

 jumping and moving both feet simultaneously to scuff dirt and leaves 

 out toward the rear. But scratching is not as incessant in the canyon 

 towhee as in the rufous-sided and green-tailed towhees, nor does it 



