MIGRATION . 265 



III. Mr. Brewster's Theory of Migration. 



" 1. Species which migrate exclusively by night habitually 

 feed in or near the shelter of trees, bushes, rank herbage or 

 grass, and when not migrating are birds of limited powers of 

 flight and sedentary habits, restricting their daily excursions 

 to the immediate vicinity oi; their chosen haunts. As a rule 

 they are of timid, or at least retiring disposition, and when 

 alarmed or pursued seek safety in concealment rather than by 

 extended flights. 



"2. Species which migrate chiefly, or very freely by day, 

 habitually feed in open, exposed situations, and in their daily 

 excursions for food often cover considerable distances. As a 

 rule they are of a bold, restless disposition, and when alarmed or 

 pursued seek safety in long flights rather than by concealment. 



"3. Species which migrate exclusively by day, habitually 

 feed either on the wing or over very extensive areas. In dis- 

 position they are either trustful and unsuspecting, or wary 

 and self-reliant. Without exception they are birds of strong, 

 easy flight, and rely solely on their wings for escape from 

 danger. 



" These premises lead easily, if not irresistibly, to the con- 

 clusion that : 



" Timid, sedentary, or feeble-winged birds migrate by night 

 because they are either afraid to venture on long, exposed 

 journeys by daylight, or unable to continue their journeys day 

 after day without losing much time in stopping to search after 

 food. By taking the nights for travelling they can devote 

 the days entirely to feeding and resting in their favorite haunts. 

 Good examples are the Thrushes (except the Robin), Wrens, 

 Warblers, and Vireos. 



" Bold, restless, strong-winged birds migrate chiefly, or very 

 freely, by day, because, being accustomed to seek their food 

 in open situations, they are indifferent to concealment, and 

 being further able to accomplish long distances rapidly and 

 with slight fatigue, they can ordinarily spare sufficient time 



