152 THE BIOLOGY OF BIRDS 



mountains. Those that followed the last alternative are the 

 relicts, and a good example is the ptarmigan. It is a 

 distinctively northern bird, and in the more southerly part 

 of its range it is confined to high altitudes. In Scotland 

 it has disappeared from the southern counties. On the 

 Cairngorms and other Highland mountains it keeps its 

 foothold — a non-migratory relict. It can thrive on berries 

 and shoots ; it has a strong heart ; it turns white in winter ; 

 and perhaps there is a touch of perfection in the way it 

 moults its worn claws and finds fresh ones ready under- 

 neath. 



The second contingent of mountain birds consists of 

 insurgent colonists from the crowded low grounds. Just 

 as the industrious Swiss migrate in the summer to their 

 *' alps," and feed an astonishing number of cattle on these 

 high mountain-shelves, so many birds and mammals have 

 colonised the heights, but more permanently. As an instance 

 we would cite the Golden Eagle. On the whole, it seems 

 justifiable to regard it as a colonist of the heights, that has 

 followed in the track of such palatable creatures as the grouse 

 and the Mountain Hare. It is a slowly multiplying bird, 

 in a high degree an aristocrat, somewhat of a specialist 

 in its diet, and it has sought out a mountain-home of 

 its own, where it can live dangerously and yet survive. 

 Other examples of this contingent would be the rock- 

 creeper, the rock-thrush, the Alpine swift, and the snow- 

 finch. 



The third set of mountain birds includes the refugees, 

 hard-pressed creatures that have sought out an asylum — 

 a way of escape from the too intense competition of the 

 crowded low grounds. As an instance we may take the 

 dipper or water-ouzel, a bird particularly fond of mountain- 

 streams, going up as high as there is rippling water. The 

 water-ouzel has a brilliant white breast, and it is often 

 difficult to be sure whether we are looking at the bird or the 

 foam of the water as it breaks over a stone. It is a near 

 relative of the wrens, that has found its niche of opportunity 

 in becoming aquatic and going high up. It walks on the 



