NESTS AND NO NESTS. 



and the martins are specialized sparrows. (I 

 use both words, bien entendu, in quite their 

 widest and most Pickwickian evolutionary 

 acceptation.) The swift and the night-jar 

 belong to one great family of birds ; the 

 swallow, the house-martin, and the sand- 

 martin to another. The likeness in form 

 and in mode of flight has been brought 

 about by similarity in their style of living. 

 Two different birds of two different types 

 both took, ages since, to hawking after flies 

 and midges in the open air. Each group was 

 thus compelled to acquire long and powerful 

 wings, a light and airy body, a good steering 

 tail, a wide gape of mouth, and a rapid 

 curved flight, so as to swoop down upon and 

 catch its petty prey unsuspected. So, in the 

 long run, the two types which hawk most 

 in the open, the swifts and the swallows, 

 have grown so like that only by minute 

 anatomical differences can we refer the 

 remoter ancestry of one species to the 

 woodpeckers and humming-birds, and the 

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