CHAP. XXI. THE TUNDRA. 269 



gently sloping towards the north-east, lying between the 

 lagoon and the inland sea — exactly the place that one would 

 expect them to breed in, not too swampy, but probably the 

 coolest place the birds could have chosen. The Pytkoff 

 Mountains, though at a considerably greater elevation 

 (513 feet above the level of the sea), are no doubt warmer, 

 because more inland. The sandy shore, having little or no 

 cover, would also be hotter from the sun. Facing the north- 

 east, this part of the tundra catches the most of the pre- 

 vailing winds at this season of the year, and the least sun ; 

 and no doubt the large bay or inland sea on one side, and 

 the open water on the other, help to cool the air. The 

 choice of a breeding-place bears only a secondary relation to 

 latitude, longitude, or elevation. It is inaccurate to state 

 that at the westerly or southerly limit of their distribution 

 birds breed at the greatest elevation. This may or may not 

 be the case, according to circumstances. The whole question 

 is doubtless one of temperature ; and the true statement of 

 the case must be, that at the warmest limit of their dis- 

 tribution birds choose the coolest locality in which to breed — 

 a statement which almost amounts to a platitude, but one, 

 nevertheless, that cannot be too constantly remembered by 

 field-naturalists in search of undiscovered breeding-grounds. 



We had already given names to the different sorts of 

 ground on the tundra. The dry, grassy hills were the shore- 

 lark ground ; the dead flat bog, intersected with tussocky 

 ridges, was the grey plover ground; the swampy marsh, 

 covered with long grass, was the reeve ground. Where the 

 grass was shorter and more tangled and knotted it became 



