96 BULLETIN 16 2, UNITED STATES NATIONAL MUSEUM 



pies the range from Wyoming and south-central Idaho north to 

 western Alberta and central British Columbia and west to eastern 

 Oregon and Washington. D. o. flemingi is found in northern 

 British Columbia, southern Yukon, and southwestern Mackenzie. 



Although technically nonmigratory, both the dusky and the sooty 

 grouse have the curious habit of performing a postbreeding vertical 

 migration. The cocks will sometimes move to the higher elevations 

 while the hens are still incubating their eggs, usually in July or 

 early in August. The females and half-grown young follow, so that 

 by the last of September the species has deserted the breeding 

 grounds. The winter months are usually spent in the upper spruce 

 forests, the birds living entirely in the trees. By May or June they 

 have descended again to their breeding areas. 



Egg dates. — Colorado and Utah (ohscurus) : 18 records, April 

 17 to July 1 ; 9 records, May 21 to June 13. British Columbia and 

 Alberta to Idaho and Wyoming (ric hards oni) : 15 records, May 3 

 to August 20 ; 8 records, May 13 to June 23. 



DENDRAGAPUS OBSCURUS RICHARDSONI (Douglas) 

 RICHARDSON'S GROUSE 



HABITS 



The name D. o. richardsoni was applied to all the " blue grouse " 

 of the northern Kocky Mountain region until, in 1914, the bird of 

 the extreme north was separated under the name flemingi, the next 

 form. Richardson's grouse is now restricted to the intermediate 

 territory, from central British Columbia and western Alberta to 

 eastern Oregon, south-central Idaho, and Wyoming. It differs from 

 the southern bird, ohscurus, in having no very distinct, terminal, 

 gray band on the tail, and from the northern bird, -flemingi, in be- 

 ing lighter colored. It does not differ materially from either in 

 its habits, except as hereinafter mentioned. 



M. P. Skinner (1927) writes: 



Here in the Yellowstone National Park, we are in the borderland occupied 

 by both the southern and northern forms. It is very difficult to place these 

 Park birds under either ooscurus or richardsoni, for there are birds of each 

 form present and all degrees of graduation between them. I once found a 

 bird dead near the Buffalo Ranch that had no band at all on the end of its 

 tail. Twice I have seen very dark birds with only a slight amount of gray 

 tipping their tails, so that they were more typical of the Sierra Mountain 

 form. Another time, I found a bird so tame that I could approach close 

 enough to determine positively that he had more than three-quarters of an 

 inch of gray on the ends of the middle tail-feathers. At other times, I 

 have found feathers with terminal bands more than a half inch wide. There 

 does not seem to be any segregation of the two forms within the Park, but, 



