THE BIRDS 199 



of spring is the appearance of our feathered friends that 

 are returning from the warmer climes in which they have 

 passed the winter. Scarcely is the snow off the ground, 

 and sometimes even before, when flocks of birds may be 

 seen on their northward journey. Not all birds migrate. 

 Some of the birds of a given locality, like the English spar- 

 rows, are permanent residents. Some, on the other hand, 

 appear only in winter, having migrated from colder 

 climates; these are the winter residents. In most places of 

 the United States a large proportion of the birds pass 

 through the country during their journeys to and from the 

 north; these are the migrants. The distances travelled 

 by different species of migratory birds is subject to great 

 variation. Many species (robin, bluebird, meadow lark) 

 winter in the Gulf States or in Mexico, and nest in the 

 northern states or in Canada. Large numbers pass the 

 winter in Cuba and the West Indies, while many species 

 go as far south as the southern part of South America. 

 The golden plover has one of the longest migration routes 

 known. After passing the winter from Patagonia to 

 southern Brazil it does not stop in its northward journey 

 until it reaches its breeding grounds within the Arctic 

 Circle, a distance of nearly ten thousand miles. Migrating 

 birds frequently keep near prominent landmarks, sucli as 

 coast lines, mountain chains or rivers. T,he Mississippi 

 valley forms a great highway for hosts of birds, and the 

 same is true only to a less degree of smaller streams. 

 The timbered tracts along the streams form excellent 

 guides for birds flying at any considerable height. Mi- 

 grating birds commonly fly very high, in some cases at 

 least a mile above the earth, and with their acute vision 

 they are able to survey an immense territory. They have 

 a marvellous ability to find their way back to their old 

 breeding grounds. It is not uncommon for the same birds 



