TRAVELS OF WATERFOWL 



overland, as to Fannestelle, they may follow cues presented by blocks of 

 woodland, by stream and river valleys, and, at their destination, by the 

 varying pattern of the fields. Perhaps such man-made features as main 

 roads, grain elevators, and city lights serve in orientation. In 1953 I found 

 a heavy flight of stubble Mallards regularly coursing down a quarter-mile 

 stretch of railway track on flights from grain fields to Longburn Creek, 

 which they then followed to the marsh. 



No doubt the sun, as the studies of Kramer ( 1951, 1952 ) and Matthews 

 (1951a, b; 1952) suggest, is of importance in the bird's orientation in space, 

 not only when it is directly east or west at dawn and dusk, but through 

 the day. We most readily think of cues to orientation as "landmarks," but 

 certain details of the sky may be important. For example, regularly in fall 

 and spring, and often during summer, thermal currents build a layer of fair- 

 weather cumulus clouds over the Portage Plains, but these are not produced 

 over the colder lake. The result is a sharp line between cloud and blue sky 

 that precisely marks the edge of Lake Manitoba. This effect may last all 

 day, sometimes a regular local feature for many days. I have seen this edge 

 of clouds from the Riding Mountains, seventy miles away; and regularly 

 we see the same cloudline over Lake Winnipeg, sixty miles east of Delta. 

 In summer, thunderheads build up on the west shore of Lake Manitoba 

 and in the interlake country to the east. These often hold their position 

 through much of the afternoon and evening; and their tops may be seen 

 for a hundred miles, lighted clearly long after the countryside is in dusk. 

 Mirage frequently lifts details of the landscape above the true horizon, and 

 I have seen the ice on Lake Manitoba from a distance of eighteen miles. 



Edge of cloud bank over south shore of Lake Manitoba. This line of clouds marks 

 the position of the lake for the traveler still many miles away. 



