CLASS AVES 623 



the bottom of lakes and ponds. This is now known to be incor- 

 rect, and when birds disappear in the fall they depart to spend 

 the winter in a more congenial southern climate. 



Migration means moving from one place to another, and the 

 idea of distance is emphasized. Birds are the most famous of 

 all animals from the standpoint of their migrations. As winter 

 approaches in the north temperate zone, they gather together 

 in flocks and move southward, returning on the advent of the 

 following spring. Birds that breed farther north spend the 

 winter in parts of the temperate zone: 



Not all birds migrate, for example, the great horned owl and 

 bob-white remain with us throughout the winter. Certain other 

 birds move southward only when the weather becomes very 

 severe. 



One of the most remarkable of all migratory birds is the golden 

 plover. These plovers arrive in the " barren grounds " above 

 the Arctic Circle the first week in June. In August they fly 

 to Labrador, where they feast on the crowberry and become very 

 fat. After a few weeks, they reach the coast of Nova Scotia, and 

 then set out for South America over twenty-four hundred miles 

 of ocean. They may or may not visit the Bermuda Islands and 

 the West Indies. After a rest of three or four weeks in the West 

 Indies or northern South America, the birds depart and are next 

 heard from on their arrival in southern Brazil and Argentine. 

 Here they spend the summer, from September to March, and then 

 disappear. Apparently they fly over northern South America, 

 and Central America, and over the central portion of North 

 America, reaching their breeding grounds in the Arctic Circle 

 the first week in June. The elliptical course they follow is ap- 

 proximately twenty thousand miles in length, and this remark- 

 able journey is undertaken every year for the sake of spending 

 ten weeks in the bleak, treeless, frozen wastes of the Arctic 

 Region. 



Most birds migrate on clear nights at an altitude sometimes of 

 a mile or more. Each species has a more or less definite time of 



