THE MOUNTAINS 357 



The mercury passed below the freezing point nightly, 

 skimming the newly opened water with ice ; snow, sleet and 

 hail-storms raged violently if brieflly, but the flowers smiled 

 bravely through the frost crystals, with not so much as a 

 wilted petal to show for the experience. 



I had come to this ' ' top of the world ' ' to make studies 

 and secure material for a group of Arctic- Alpine birds, not- 

 ably the Eosy Snow Finch, (Leucosticte tephrocotis), and 

 White-tailed Ptarmigan, (Lag opus leucurus). No birds 

 could emphasize more strongly the boreal character of the 

 life of these mountain summits. Snow Finches are found at 

 sea-level only north of the sixty-eighth degree of latitude 

 and extend southward, above timberline, in the Eockies, to 

 Colorado, where they nest at 11,500 feet altitude, and in the 

 Sierras, to Mount "Whitney, California, where they sum- 

 mer as low as about 9500 feet. They are said not to descend 

 below timberline during the summer, but we noted a striking 

 exception to this rule at Lake Louise, where numbers of 

 them came regularly to feed, about the forest-surrounded 

 stable. They were evidently attracted by the fallen grain 

 and may have learned of this supply of food during the win- 

 ter when the heavy snowfall drives them to lower levels. 



The Ptarmigan is a characteristic circumpolar type which 

 also finds a congenial home in comparatively low latitudes 

 at correspondingly high altitudes, ranging, in the Coast 

 Eange, as far south as Oregon, and in the Eockies reaching 

 northern New Mexico. Its distribution is not continuous, 

 there being many breaks in the Alpine portions of these 

 mountain chains, such, for example, as separate the Eockies 

 of Colorado from the main chain to the northward. The 

 Ptarmigan of Colorado and New Mexico, therefore, cannot 

 have acquired their present distribution by extension of 

 range southward under existing conditions, but are evident- 

 ly to be classed with the group of northern plants and ani- 

 mals, which, brought south during the Glacial Period, were 

 left stranded on Arctic- Alpine islands by the retreating ice. 



