2i8 SAND-GROUSE 



serve to show that it would or might be well ia 

 dealing with the problem to view it in its widest 

 aspect — to regard migration as originating in an 

 impulse common in the animal world, from mammals 

 to insects. From this impulse the instinct itself has 

 been evolved and brought to a high state of perfec- 

 tion in some birds. Nevertheless we can see that in 

 all cases, even in the most perfect, it is Hable to 

 derangement, so that an entire race, or even species, 

 might be driven by it to destruction. Thus, we have 

 seen on several occasions that the sand-grouse, which 

 in Central Asia has a perfect migration, has gone 

 wrong, and instead of flying north and south has 

 rushed away west all over Europe, to perish at last 

 in the sea. 



It is not necessary to suppose that a similar 

 disaster overtook the famous passenger pigeon and, 

 a little later, the golden plover, Eskimo curlew, 

 pectoral sandpiper and upland plover, since, as we 

 have seen, the deadly war waged against the birds 

 in North and South America during the last four 

 or five decades sufficiently accounts for the dis- 

 appearance of these species. 



The fact that so highly perfected a species as 

 PaUas's sand-grouse, in its organism, instincts and 

 habits so admirably adapted to its peculiar environ- 

 ment, so hardy and abounding in vitality, should 

 on occasions be driven away in a wrong direction, 

 to end its flight when exhausted in lands and climates 

 unsuited to it, or flying beyond Europe to perish in 

 the sea, is enough to show that bird migration too, 



