SAND DUNES AND SALT MARSHES 



still poured by in the gathering dusk, while 

 the air to the north and west appeared filled 

 with black forms against the luminous yellow 

 haze made by the rays of the departed sun. 

 At ten minutes past seven, already dusk, the 

 birds were pressing on in undiminished num- 

 bers. Two minutes later they suddenly 

 stopped coming, with the exception of a few 

 stragglers, while a great mass of whirling, 

 twittering birds could be seen over the birch 

 thicket to the south. A minute later, at thir- 

 teen minutes after seven, another army of 

 birds was flying south, but the movement 

 ceased at a quarter past seven, although a 

 few belated ones straggled by in the darkness. 

 At half -past seven I ventured to investigate 

 the roost, which I found to be somewhat over 

 an acre in extent and to consist of small birch 

 trees about fifteen feet high, closely crowded 

 together. The blackness of the undergrowth 

 of ferns was relieved by the numerous white 

 droppings of the roosting birds. In the dark- 

 ness not a swallow could be seen amid the 

 thick foliage, but a constant conversational 

 twittering revealed their presence. As I en- 

 tered the grove the noise became greater, and 

 a number of birds above my head took flight, 



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