MIGRATIONS OF WATERFOWL 



the evening of May 1 at 7 p.m. a pair of Shovellers flying at about 100 

 feet came directly toward the radar, and when they were at a distance of 

 about 150 feet, the radar was directed upon them. The birds literally col- 

 lapsed in midair, dropping at least twenty feet as if shot; then, regaining 

 flight, they altered their direction to go away at right angles to the original 

 course. This was a dead-calm evening, and the observers were well hidden. 

 In any event, had the birds been disturbed by the watchers they should 

 have swung upward rather than dropping. The same evening a band of 

 four Shovellers flying toward the scanner dropped nearly fifty feet out of 

 the sky the moment the radar was directed at them, almost reaching the 

 ground before regaining controlled flight. 



All the foregoing observations were made of ducks coming toward the 

 radar and flying over it. There were many daily opportunities to direct the 

 radar at local ducks going east or west along the shoreline of Cadham Bay, 

 but no response was ever observed in any of these waterfowl crossing the 

 beam. Nor did we detect any response in the wild and tame ducks and 

 geese at rest in the Station enclosure to suggest that they were aware when 

 the radar was directed at them, as it was for many minutes at a time. 



Although few waterfowl crossed over the radar, hundreds of the four 

 species of blackbirds migrated toward and over as they traveled west along 

 the ridge. The radar was aimed at every crossing flock, such birds sometimes 

 coming within fifty feet; but there was never a single response in more than 

 a hundred tests. The same held true for heavy numbers of Tree Swallows, 

 Franklin's Gulls, Juncos, and Flickers that crossed close to the scanner beamed 

 in their direction. Drost ( 1949 ) also found specific variations in the response 

 to radar; Kramer ( 1951 ) reported negative results with Red-backed Shrike; 

 Matthews (1951a) saw no evidence of awareness in homing pigeons released 

 in a radar beam. We do not understand the reasons for these differences, 

 much less how the radar pulsations are perceived by some waterfowl. The 

 whole subject offers an interesting and important field for continued re- 

 search. 



So far we know only that some birds, such as ducks, under certain situa- 

 tions apparently respond to radar pulsations in much the same manner as 

 they do to a shotgun blast. But, as Drost explains (1951), "we do not sug- 

 gest that birds are guided by waves, if we mention the fact that migrants 

 show a positive reaction to ultra-shortwave (radar) transmission (Drost, 

 1949); we shall only mention that birds are able to react in cases where 

 men are unable to do so." In his recent review of the studies of bird naviga- 



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