26 
WILD SCENES AND SONG-BIRDS. 
furthermore, in tlie fact, tliat by tlie time dark had set in, 
they were all quiet — sitting, black and still, in heaped cones, 
as they were defined 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 
