26 WILD SCENES AND SONG-BIEDS. 



furthermore, in the fact, that by the time dark had set in, 

 they were all quiet sitting, black and still, in heaped cones, 

 as they were denned against the dim sky ; while in a pigeon 

 roost, the heavy thundering of restless wings continues to 

 roll on, without interval, until just before day. 



This interesting fact in relation to the habitudes of the crow, 

 and which I have observed to occur only in the winter, when 

 they need the animal heat arising from the mutual contact of 

 their many bodies as a protection from the extremities of cold, 

 is an extraordinary example of that reasoning adaptation of 

 the means to the end upon which I insist. 



This same incident, of the departure upon so large a scale of 

 every creature from its usual habits, under the force of cir- 

 cumstances, is only paralleled by another fact which, though 

 not mentioned either in any of the books of Natural History, 

 I know to be strictly true. It refers to an occasional mode 

 of Hybernating resorted to by the Prairie Hen, or Pinnated 

 Grouse. 



The most extraordinary phenomenon produced by the neces- 

 sities of the climate, and as a protection against the terrible 

 winds which sweep over these apparently illimitable levels, at 

 the approach of winter, consists, in the assembling of these 

 birds, from a distance of many miles around, to roost on the 

 same spot, something after the manner of the Wild Pigeon. 

 This fact seems also to have escaped Mr. Audubon's notice. 



At the opening of winter, a spot is selected, on the open 

 prairies, in the upper part of the Missouri country, which is 

 more sheltered than the surrounding region, by the character 

 of the ground, from the biting force of the north-west winds. 

 Here the Prairie Hens begin to assemble early in the even- 

 ing, and by the time dusk comes on immense numbers are 

 collected. They approach the scene in small flocks, in a leis- 

 urely manner, by short flights. They approach the place of 

 gathering silently, with nothing of that whirr of wings, for 

 which they are noted when they are suddenly put up, but 

 they make ample amends when they arrive ; as in the Pigeon 



