SAND DUNES AND SALT MARSHES 



sponse to some mysterious signal, mount into 

 the air in irregular circles, at times drifting 

 together and whirling about like masses of 

 smoke, all the time rising higher and higher. 

 "WTien so high that the individual birds can 

 with difficulty be distinguished, they move off 

 towards the south, and with their rapid flight 

 are soon lost to sight. With the evidence of 

 migration so apparent, it is a curious fact that 

 for many years it was believed that swallows 

 retired to the bottoms of ponds in the fall and 

 spent the winter dormant in the mud! 



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