BIRD MIGRATION. 19 



DIRECT AND CIRCUITOUS MIGRATION ROUTES. 



All black-poll warblers winter in South America. Those that are 

 to nest in Alaska strike straight across the Carribbean Sea to Florida 

 and northwestward to the Mississippi River (see fig. 5). Then the 

 direction changes and a course is laid almost due north to northern 

 Minnesota in order to avoid the treeless plains of North Dakota. 

 But when the forests of the Saskatchewan are reached the northwest- 

 ward course is resumed and, with a slight verging toward the west, 

 is held until the nesting region in the Alaska 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 whiter 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 (see fig. 6), 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 night- 

 fall, 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 evolu- 

 tions, 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 migration route are but a tithe of the distance 

 the bird covers in pursuit of its daily food. 



The cliff swallow spends the winter in Brazil and Argentina and 

 breeds from Mexico to Alaska. Writing 10 years ago concerning it, 

 the author made the following statement: 



It would be expected to reach the United States in spring first in southern Florida 

 and Texas, later in the Rocky Mountains, and finally on the Pacific coast. Aa a 

 matter of fact, the earliest records of the bird's appearance in spring come from northern 



