A WINTER CROW ROOST 141 



to count them. From our point of vantage in a 

 spruce thicket on the hill we can see that this 

 flock stretches for two miles into the dunes and 

 it takes four minutes to pass. The sj^eed of 

 flight, therefore, must be roughly about thirty 

 miles an hour. At 4.15 p. m. the sun sets, but 

 in the yellow glow of the cloudless sky the birds 

 can be seen pouring by from the west and south. 

 The bulk of the stream from the north now comes 

 to rest on the hillside for only occasionally can 

 a crow be seen flying to the south over the heads 

 of the southern stream. 



At 4.35 P. M., Dr. Tyler and I again counted 

 the southern stream for a minute as they flew 

 silently between us and the lighthouse. One of us 

 counted 160 the other 157 birds, so it is probable 

 that our counts were fairly accurate. This con- 

 stant watching of the black stream from the 

 south against the white lighthouse produced in 

 both of us a curious optical illusion. The light- 

 house and dunes seemed to be moving smoothly 

 and swiftly from north to south I 



At 4.37 P.M., a great cawing arose from the 

 hillside and a black cloud of birds rose up, some 



