MANNER OF MIGRATION. 55 



ciated with the young. Some fly by day, some by night, 

 and others by both day and night. This fact was first 

 established by Mr. Wilham Brewster, who, in his admi- 

 rable memoir on Bird Migration, writes : " Timid, seden- 

 tary, or feeble-winged birds migrate by night, because 

 they are either afraid to venture on long, exposed jour- 

 neys by daylight, or unable to continue these journeys 

 day after day without losing much time in stopping to 

 search for food. By taking the nights for traveling 

 they can devote the days entirely to feeding and resting 

 in their favorite haunts. Good examples are Thrushes 

 (except the Eobin), 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 con- 

 cealment, and being further able to accomplish long dis- 

 tances rapidly and with slight fatigue, they can ordi- 

 narily spare sufficient time by the way for brief stops 

 in places where food is abundant and easily obtained. 

 Under certain conditions, however, as when crossing 

 large bodies of water or regions scantily supplied with 

 food, they are sometimes obliged to travel partly, or per- 

 haps even exclusively, by night. Excellent examples are 

 the Eobin (Merula), Horned Lark {Otocoris\ and most 

 IcUridm [Bobolink, Blackbirds, and Orioles]. 



" Birds of easy, tireless wing, which habitually feed in 

 the air or over very extensive areas, migrate exclusively 

 by day, because, being able either to obtain their usual 

 supply of food as they fly, or to accomplish the longest 

 journeys so rapidly that they do not require to feed on 

 the way, they are under necessity of changing their usual 

 habits. The best examples are Swallows, Swifts, and 

 Hawks." 



While migrating, birds follow mountain chains, coast- 

 lines, and particularly river valleys, all of which become 



