The Bird Itself 3 



shafts; the rump is somewhat more rufous than the back; the wings 

 usually show less rufous in the browns than the other upper parts, 

 the primaries are quite dark with buff to whitish markings along the 



Fig. 1. The twelve grouse shown represent parents and a brood of grouse. We 

 assume that the parents survived the vraiter on an area that has a carrying ca- 

 pacity of but two grouse. Therefore ten of this group must die by next spring if 

 they remain in the area vmder the same conditions. The birds are illustrated as 

 meeting the elements that may reduce their numbers. The higher the element, 

 the greater the toll it may possibly take. The highest element, here shown as 

 shelter, is the hmiting factor. Only two grouse, in this instance one youngster 

 and one parent, are able to surmount it. The reduction or eUmination of any of 

 the other seven lower elements would not result in a greater survival but merely 

 a delayed mortaHty, since the shelter will permit the maintenance of only two 

 grouse. Under difFerent circumstances the eight factors might assume any order 

 of importance, and any one might be the limiting factor. 



narrow outer vanes; and the secondaries and coverts are bordered 

 with buff or whitish with occasional black spotting. 



The ground color of the eighteen^ tail feathers (rectrices) is a 



^A few specimens having twenty rectrices have been examined, usually males, 



and a few with only sixteen, usually females. ''^l C/ / 



