BIRD MIGRATION xi 



Gulf route night after night for nearly eight months in the year myriads of hardy migrants 

 wing their way through the darkness toward an unseen destination. 



To the w^estward a short route stretches a few hundred miles from the coast of Texas 

 to northern Vera Cruz. It is adopted by some Warblers, as the Kentucky, the Worm-eating, 

 and the Golden-winged, and a few other species, which seek in this way to avoid a region 

 scantily supplied with moist woodlands. 



Still farther west are two routes which represent the land journeys of those birds from 

 western United States that winter in Mexico and Central America. Their trips are com- 

 paratively short ; most of the birds are content to stop when they reach the middle districts 

 of Mexico and only a few pass east of the southern part of that country. 



Still another route is one which extends in an approximately north and south line from 

 Nova Scotia to the Lesser Antilles and the northern coast of South America. Though more 

 than a thousand miles shorter than the main migration route, it is not employed by any land 

 bird. But it is a favorite fall route for thousands of water birds, notable among which is 

 the Golden Plover. 



All Black-poll Warblers winter in South America. Those that are to nest in Alaska 

 strike straight across the Caribbean Sea to Florida and northwestward to the Mississippi 

 River. Then the direction changes and a course is laid almost due north to northern Minne- 

 sota in order to avoid the treeless plains of North Dakota. But when the forests of the vSas- 

 katchewan are reached the northwestward course is resumed and, with a slight verging 

 toward the west, is held until the nesting region in the Alaskan spruces is attained. 



Cliff Swallows in South America are winter neighbors of the Black-poll Warblers. But 

 when in early spring nature prompts the Swallows which are to nest in Nova Scotia to seek 

 that far-off land, situated exactly north of their winter abode, they begin their journey by 

 a westward flight of several hundred miles to Panama. Thence they move leisurely along 

 the western shore of the Caribbean Sea to Mexico, and, still avoiding any long trip over 

 water, go completely around the western end of the Gulf. Hence as they cross Louisiana 

 their course is directly opposite to that in which they started. A northeasterly flight from 

 Louisiana to Maine and an easterly one to Nova Scotia completes their spring migration. 

 This circuitous route has increased their flight more than 2,000 miles. 



Why should the Swallow select a route so much more roundabout than that taken by 

 the Warbler? The explanation is simple. The Warbler is a night migrant. Launching 

 into the air soon after nightfall, it wings its way through the darkness toward some favorite 

 lunch station, usually one to several hundred miles distant, and here it rests and feeds for 

 several days before undertaking the next stage of its journey. Its migration consists of a 

 series of long flights from one feeding place to the next, and naturally it takes the most direct 

 course between stations, not avoiding any body of water that can be compassed in a single 

 flight. 



The Swallow, on the other hand, is a day migrant. It begins its spring migration several 

 weeks earlier than the Warbler and catches each day's rations of flying insects during a 

 few hours of slow evolutions, which at the same time accomplish the work of migration. 

 Keeping along the insect-teeming shores, the 2,000 extra miles thereby added to the migra- 

 tion route are but a tithe of the distance the bird covers in pursuit of its daily food. 



The normal migration route for the birds of eastern North America is a northeast and 

 southwest course approximately parallel with the trend of the Atlantic coast; the birds 

 breeding in the interior take a line of flight parallel in general with the course of the three 

 great river valleys — those of the Mississippi, the Red, and the Mackenzie — that form a 

 highway rich in food supplies between their winter and summer homes. Many birds, how- 

 ever, follow migration routes widely differing from the normal. One of the most extreme 

 exceptions is that of the Marbled Godwit. Formerly a common breeder in North Dakota 

 and Saskatchewan, some individuals on starting for their winter home in Central America 

 took a course almost due east to the Maritime Provinces of Canada and thence followed 



