MAGNETIC AND RADIO FIELDS 



established there, from April 21 to May 1, 1949, through the cooperation of 

 the Royal Canadian Air Force.* This was a small aircraft type ADS operat- 

 ing on a 3-cm. band with a peak output of 50 kw. The scanner was set up 

 on the roof of a garage at the edge of the Station, with the rest of the 

 equipment inside, except for the generator operating beside the building. 



The location was under a heavily used migration pass, and the calendar 

 period was for the usual peak of the spring migration. It so happened, how- 

 ever, that the weather was unfavorable for waterfowl migration throughout 

 the test, and fewer ducks passed over during the whole period than would 

 be expected in one evening. During the eleven days, the radar was directed 

 at only fourteen flocks of ducks migrating over the pass. These bands of 

 Mallard, Pintail, and Lesser Scaup arrived from the southeast, crossed over 

 at an elevation of 150 to 300 feet in swift, direct flight into the northwest. 

 The radar was directed at these oncoming flocks when they were 100 to 

 300 yards away. 



Twelve times out of the fourteen opportunities with migrants we ob- 

 served unexplained actions that took place the instant the radar was aimed 

 at an approaching flock: there was a marked quickening of wingbeat, the 

 birds abruptly altered their direction, and the formation was disrupted. In 

 each instance the disturbance lasted but an instant, then the flock reformed 

 and continued on its way. The radar scanner could be swung around, the 

 ducks held in its beam, but no further responses were noticed as the dis- 

 turbed flock flew past. The behavior of the birds was hardly different from 

 that of a flock fired upon with a shotgun, and I have never seen ducks behave 

 in this manner except under gunfire. The noise of the generator might have 

 disturbed them, as might the movements of observers. But migrating ducks 

 have not before nor since been abruptly frightened by people or motors in 

 the village. There was little wind throughout the tests and on several eve- 

 nings, no wind at all, hence air currents were not responsible. Four migrant 

 flocks passed directly over the radar when the generator was running, but 

 the radar not operating; these birds showed no variation in their direct pas- 

 sage over the equipment. Unfortunately, no observations were made with 

 the radar operating and the generator silent; and there were not enough 

 birds to check on disturbed and undisturbed flights with and without radar. 



In one instance, however, all other influences seemed to be ruled out. On 



* I am especially grateful to Squadron Leader J. Hudson, who arranged for this test, and 

 to Leading Aircraftsmen Douglas Hudson and Robert Stamm, who set up the radar at Delta 

 and operated it throughout. 



189 



