SOOTY GROUSE 109 



size, as well as the shape of the tail itself, is diagnostic of birds of the year. As 

 compared to that of the adult, the tail is much rounder and more fan-shaped, 

 because of the greater proportionate shortness of the lateral feathers. The 

 individual feathers are shorter, narrower, and have rounder tips. Most of 

 these rectrices are replaced during the following winter, spring, and summer, 

 but some (usually the outer pairs) are apparently always retained until the 

 following fall. The replacement-feathers are similar to those of the adult. 

 However, the whole tail (replacement and first winter feathers alike) is cast 

 at the second fall moult, at which time the longer and broader tail-feathers 

 of maturity are acquired. Replacement is so invariable as to preclude the pos- 

 sibility of accidental or fortuitous moult. These differences are most easily seen 

 in males. They are present in females in lesser degree. 



The first winter plumage is much like the adult and the sexes are 

 quite unlike; but young birds, during the first year, can always 

 be recognized by the outer primaries, by the shape of the tail, and 

 by the narrow tail feathers. There is little evidence of even a very 

 limited prenuptial molt, but a complete postnuptial molt takes 

 place the next summer, which produces the fully adult plumage, 

 when the bird is more than a year old. Of this Harry S. Swarth 

 (1926) says: 



The first post-nuptial molt begins about the middle of July of the second 

 year and lasts until about the middle of September. The change in character 

 of rectrices is the one conspicuous feature of the mature plumage. I cannot 

 find that there is any renewal of rectrices (except sporadically, presumably as 

 the result of accidental feather loss) until this molt regularly begins. This, 

 I believe, is the only point in which I disagree with van Rossem in the con- 

 clusions drawn by him regarding molt in this genus. The fully adult tail, now 

 acquired, is square ended, the feathers broad and truncate. Minor color dif- 

 ferences are a clearer gray coloration below and less white spotting on breast 

 and sides, while the mottling on dorsal surface of wings and on interscapulars 

 is less in extent, and gray instead of brown. 



According to A. W. Anthony (1899) the sooty grouse has been 

 known to hybridize with the ring-necked pheasant. 



Food. — Dr. Sylvester D. Judd (1905a) sums up the food of the 

 "blue grouse" (various races), as follows: 



The food consisted of 6.73 percent animal matter — insects, with an occa- 

 sional spider — and 93.27 percent of vegetable matter — seeds, fruit, and leaves. 

 Grasshoppers constitute the bulk of the animal food, amounting to 5.73 per- 

 cent. Beetles, ants, and caterpillars form the rest of the insect food. One 

 stomach contained the common land snail (Polijgyra sp.). 



Of the vegetable food, he says : 



Browse is eaten by the blue grouse to the extent of 68.19 percent of its 

 annual food, and is distributed as follows : Buds and twigs, 5.2S percent ; 

 coniferous foliage, 54.02 percent; other leaves S.89 percent. The species 

 spends most of its time in pine forests feeding on needles, buds, and flowers. 

 The yellow pine (Pinus ponderosa) — male flowers, the white fir (Abies 

 concolor), Abies magnified, the Douglas fir (Pseudotsuga mucronata), the 

 western hemlock (Tsuga heterophylla), and the black hemlock (Tsuga mer- 



