978 



AMERICAN FORESTRY 



entirely and spend the winter in Central Aineriea or 

 northern South America. A few species like the bobo- 

 link, night hawk and golden plover, pass over the moun- 

 tains of northern South America to winter on the pampas 

 of Brazil and Argentine, while a few others amongst 

 the shore birds, the knot and yellowlegs, for example, 

 wander to southern Patagonia. 



( hie of the strangest features of the migrations of 

 some of these birds that winter in South America is 



THK CHICKADEE 



One of the liirds that does not migrate and which is enaliled to accommn 

 (late itself to the rigors of the northern winter. The nuthatches and 

 vvoodijeckers also share the northern winter with it. 



that they pursue different routes in the spring from those 

 in the fall. The golden plover, for example, which nests 

 along the Arctic coasts of North .'\merica in the fall, fly 

 southeast to Labrador and thence due south to vSouih 

 America, a few stopping along the Atlantic coast. I'.ut 

 the majority fly directly over the sea, a distance of about 

 ;.'.M)0 miles, to the north coast of South .\merica an.l 

 thence to Argentine. At this time of the year they are 

 never seen in the Mississippi valley. In the spring, how- 

 ever, they strike United States along the C.ulf coast, and 

 all migrate up the Mississippi valley, at this season ne\er 

 being seen along the .Atlantic coast. 



I'.ut this double route is the exception. The vast ma- 

 jority of binls just move southward after the breeding 

 season, following the routes where food is most abun- 

 dant, shunning areas where food is scarce, until they 

 fnially reach their winter quarters. In the siiring they 

 ino\e northward along the same highway. 



The fall migration is markeil by much more dallying 

 than the spring and bv much more w.andering, some 

 birds dela\ing their actual migration by trips to the north, 

 east or we-^t. There is no liurrv so long as tood is 



abundant, and some birds like the snipe, woodcock and 

 many species of ducks remain until pressed for food by 

 the killing frosts or the formation of ice over their feed- 

 ing pools. Most species, however, start southward while 

 food is still abundant. 



The fact that so many species leave long before food 

 becomes scarce makes the reason for their going the more 

 strange and brings us to the question of why thev 

 migrate and how they know when it is time. The regu- 

 larity with wdiich birds arri\e in the spring has been 

 observed since ancient times, but it has not been until 

 the modern investigations that we have understood the 

 delicate physiological adjustment wdiich records time for 

 the bird almost as accurately as a timepiece. The physio- 

 k.igical cycle is as precise in a healthy bird as is the revo- 

 lution of the wheel of an engine. The bird's year begins 

 with the slightest increase in the size of the reproductive 

 organs, for they are not, as in some of the higher ani- 



THE .ME.\DOW L.\RK 



These birds, wiiich nest throughout most of the United States and 

 Canada, merely withdraw into the southern part of their breeding 

 range during the winter while their places are taken by such birds as 

 the tree sparrow, snow bunting, pine grosbeak and siskin that nest in 

 northern Canada and migrate in winter as far south as northern 

 I'nited States. 



mals, of constant size throughout the year. The increase 

 is a sign that the breeding season is approaching and 

 with migrating species there comes the concomitant in^ 

 stinct to migrate and the bird begins its journev to the 

 breeding ground. If there were no such thing as weather, 

 if food were always equally abundant, the bird would 

 arrive at its nesting ground on exactly the same dav each 

 year. Indeed, this is saiil to be the case with some of 

 the sea birds, notably the puffins, which are little aft'ected 

 b\- the weather. They spend the greater part of the year 



