..^: 



Blackbirds migrating west along the lakeshore 



and 200 feet, always flying lower when moving against a wind. Crows fly 

 at elevations of less than 300 feet, often well within gun range just above 

 the trees. Flickers go along at treetop level, always as single birds, although 

 one bird is usually in sight of another. All of the swallows, blackbirds, and 

 other diurnal travelers that move with flapping flight carry on their heaviest 

 migrations during the morning, afternoon, and evening hours, resting and 

 feeding during midday. The soaring kinds, such as the broad-winged hawks, 

 travel mostly through the middle of the day when thermal currents give 

 them the greatest lift. I have seen a heavy migration of Rough-legged 

 Hawks end abruptly as the wind died, almost every lone tree far and wide 

 across the prairie suddenly boasting two or three, sometimes a dozen or 

 more, of these big birds. 



On a day of southeast wind I found the average ground speed of black- 

 birds to be thirty miles per hour and the total span of their morning and 

 evening passage eight hours. Thus many birds may have traveled more than 

 two hundred miles. If the migration had been about the same all along the 

 way, those that ended their day at Delta started well south of the interna- 

 tional border in Minnesota, while those that set out from Delta went at 

 least a hundred miles across the border into Saskatchewan. 



These hawks, blackbirds, Crows, Flickers and others continue westward 

 around the lake until reaching the mouth of the Whitemud River at the 

 southeast corner. Thence they branch into the northwest again ( Figure 18 ) . 

 This deflection away from the west shore of Lake Manitoba leaves an area 

 nearly vacant of migrants, much as the hiatus described for the north shore 

 of the Gulf of Mexico (Lowery, 1945; Williams, 1945). For example, be- 

 tween eight and eleven o'clock on the morning of April 16, 1952, Les Garn- 

 ham, posted at Delta, counted 137 flocks of blackbirds pass westward. The 



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