290 TowNSEND, Bird Genealogy. [july 



appears to be acquired later than running. It is a very interesting 

 fact that the Savannah Sparrow, frequenter of meadows and 

 marshy pastures, generally hops even when on smooth ground, 

 although it is also a good runner, while its near relation the Ipswich 

 Sparrow, frequenter of sandy wastes, almost never hops and is a 

 good walker. 



Herons as far as I know, although constantly in the water very 

 rarely swim, but that they come of a swimming ancestry seems 

 probable from the behavior of a young Green Heron not old enough 

 to fly that I put in the water. It sat erect on the surface and swam 

 off with a grace and ease that contrasted forcibly with its awkward 

 movements on land. Not only was its poise graceful and Swan- 

 like, but the speed with which it swam, the practiced manner in 

 which it feathered its ungainly toes, the ease with which it threaded 

 its way among the grass stalks, and dabbed every now and^'then 

 at the water with its bill, all pointed to an inherited instinct, an 

 instinct, however, that is largely if not entirely lost in adiilt life. 

 This young Heron had never practiced the art of swimming before 

 — it had probably never left the nesting tree, which was'on a 

 marsh island some distance from even the highest tides. Adult 

 Herons like some vShore Birds show their swimming ancestry by a 

 distinct web between the middle and outer J;oes. - 



The use of the wings under water in some diving^ birds and the- 

 significance of this fact I have already discussed in another place. ^ 



One is apt to think of evolution as a thing of the past, an ac- 

 complished fact, and to forget that at the present period of tilne 

 this great law is still as existent as it has been since the world 

 began. With change in environment, there comes through natural 

 selection acting on slight variations and occasional mutations a 

 change in the structure to fit the new environment, and in time 

 a new species is developed. As n^w 'species arose in the past, so 

 they must be in various stages of formation at the present time. 

 The great group of American Warblers are for the most part slender- 

 billed, insect-eating birds, that go south with the approach of cold 

 weather. One of them, however, is enabled to spend the winter 

 on the bleak New England coast by a change from an insectiv- 



1 Auk, XXVI, 1909, pp. 234 to 248. 



