SAND DUNES AND SALT MARSHES 



present day, the Order CJiaradriiform, or 

 plover-like birds, includes the shore-birds, 

 gulls, auks and pigeons. The shore-birds, we 

 have just seen, show evidence of a swimming 

 ancestry, although, with the exception of the 

 phalaropes, they habitually prefer the shore 

 under their feet, even if it is wet and partly 

 covered with water, to the deep sea. The 

 presence of partial webs, as in the ring-neck, 

 sand-peep and willet, point to the former ex- 

 istence of the swimming habit, rather than to 

 a beginning of this habit, for these birds, like 

 other shore-birds, do not swim except when 

 unexpectedly forced to it. 



If the partial web in the foot of the adult 

 heron and shore-bird showed the beginning of 

 the swimming habit in birds of land ancestry, 

 we should find the young birds, like the young 

 seal, very inexpert in the water. As the re- 

 verse of this is the case, our conclusion that 

 these birds are of water ancestry must be 

 correct. 



Gulls and terns have fully webbed feet, but 

 their habits at the present day hardly justify 

 them in this possession. Webbed feet are of 

 great advantage to the rapidly swimming bird 

 and to the diving bird that depends on its feet. 



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