54 MOUNTAIN AND MOORLAND 



But although Birds do not hibernate, there are a 

 few interesting cases of lying low for a short time. 

 Thus the Canadian Ruffed Grouse (Bondsa umbel- 

 latus) plunges into the soft snow of drifts and makes 

 a passage about two feet long with an enlargement at 

 the end. The loose dry snow serves as a non-con- 

 ducting garment, just as it does for the bulbs and 

 roots of plants, and the Ruffed Grouse may lie perdu 

 for several days warm beneath the snow. 



The same bird shows in winter a very neat adapta- 

 tion for walking on the surface of the loose snow 

 without sinking in. It puts on "snow shoes," in the 

 form of hard skin plates on each side of each toe, 

 reminding one a little of the scalloped margins of the 

 toes in a Grebe. The area of the foot is doubled by 

 this simple device, which spreads the bird's weight 

 over a larger surface. 



We are often impressed with the delicacy of living 

 creatures. These beautiful transparent Ctenophores, 

 or Comb-Bearers of the open sea, they sink to quiet 

 depths whenever the " white horses " begin to prance 

 on the surface. We have known of two hundred birds 

 being found dead in a small stackyard after a very 

 cold night when the temperature fell just a little below 

 the bird's limit of warmbloodedness. A slight knock 

 on the head kills the strong Mole forthwith. But at 

 other times we are impressed with the toughness of 

 life. Let us give an example. 



No place could be more inhospitable than the sur- 

 face of a glacier, unless it were an iceberg. Yet on 

 the glacier there are often great multitudes of so- 

 called " glacier fleas " not really fleas, of course, but 

 old-fashioned, primitive, wingless insects, known as 



