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through first seeking protection there during the migration, 

 as do both the BoboUnk and the Redwing at the present day. 

 That this may have happened in comparatively recent times, is 

 suggested by a number of considerations. In the first place, 

 the Redwing shows no specialization to a marsh environment 

 in either structure, food, or coloration. Secondly, it spends 

 hardly more time in the marsh than is necessary to rear its 

 young. Thirdly, it easily reverts to a dry-land nesting site 

 when driven from the marshes by any catastrophe. Fourthly, 

 it is still unable to cope with an emergency that must have 

 always arisen in connection with its marsh nesting site, namely, 

 the overturning of its nest by the growth of the vegetation. 

 Fifthly, unlike the true marsh birds, it rehes for safety pri- 

 marily upon flight and not upon the shelter of the marsh itself. 

 The Redwing is a member of a large and widely distributed 

 family of birds, which are very diverse in habits, occupy almost 

 every type of environment, and yet retain great similarity of 

 structure. The modifications occurring among the members 

 of the family are for the most part slight. The birds in this 

 group seem eminently generalized, adaptable to almost every 

 environment and to almost every food. The Redwing is as 

 generalized as any member. Its bill, for example, is heavy at 

 the base and suitable for crushing seeds, and yet it is almost 

 as finely pointed and sharply edged as a Warbler's; it is 

 shorter and heavier, relativelj^, than the Crackle's, Oriole's, or 

 Meadowlark's, but not so extreme in this respect as is the 

 Bobohnk's. The Redwing is to-day the dominant species of 

 bird found in the marsh, and it has gained this ascendancy, 

 not by permanent modification or specialization, but by a 

 generaUzation of structure and an adaptability which permit 

 it to utilize the richest resources of diverse environments. It 

 is thus freed from the dependence which restricts the more 

 specialized types of birds. Add to this the inconstancy of the 

 conditions in the marsh, which tends to limit the abundance 

 of the less adaptable species, and the dominance of the Red- 

 wing is easily understood. The Redwing is dominant because 

 it is superior to its environment. 



