HOMEWARD MIGRATION 



rived steadily from the southeast flying directly to the lakeshore. Here they 

 went one way or the other : some went up the east shore, while others turned 

 to go around the south end of the lake, this choice requiring them to make 

 nearly an about-face swing (Figure 18). This splitting of the flight did not 

 take place sharply at one point of the lakeshore, but occurred over a stretch 

 about twenty miles long. The result was a two-way flow of birds going in 

 opposite directions. This migratory divide is the same for Flickers, Crows, 

 all the hawks, and, indeed, for all the shoreline travelers, and on days when 

 there is a heavy westward flow at Delta I have seen just as steady a passage 

 to the northeast along the eastern shoreline. 



This turning place at Lake Manitoba is probably only one of several such 

 decisions the migrants must make during a day of travel. Earlier, there must 

 be a splitting of the flight when some birds branch north to Lake Winnipeg. 

 Mr. A. G. Lawrence, veteran Winnipeg naturalist, has made an energetic 

 search for this turning place of Lake Winnipeg blackbirds and believes there 

 is a major migrational divide at the bend of the Red River near Morris, 

 Manitoba, the same bend where Baldock saw the splitting of the Canada 

 Goose flock (p. 122). Of Flickers I have watched several different flight 

 lines on the same day, all stemming originally from the main current flow- 

 ing to the northwest. On April 25, 1951, I saw a steady stream of Flickers 

 going northeast across the Libau Marsh toward the east shore of Lake Win- 

 nipeg. Another flight went north up the Red River Valley. A steady move- 

 ment of Flickers went northwest over the prairie between Lake Winnipeg 

 and Lake Manitoba. There was a concentrated flow northwest along the 

 eastern shore of Lake Manitoba and a westward passage over Delta around 

 the south end of the lake. For individuals with far destinations, the wrong 

 turn in Manitoba would be as serious an error as that of a Vancouver-bound 

 railroad passenger boarding the Illinois Central in Chicago. 



These diversions of Flickers, blackbirds, and all the other birds from the 

 main currents of migration, the many separate departures from the standard 

 direction, are interesting in view of the relation between weather and mi- 

 gration. The strong southerly flow of winds favors the mass movement of 

 most birds following the standard direction ; but it is clear that the migrants 

 are by no means swept along in this current of air. When the turning point 

 is reached, the travelers bend this way or that, even though they must now 

 cross the wind rather than go with it. Blackbirds making the turn around 

 the south end of Lake Manitoba are obliged to face the wind for a while in 

 order to follow their chosen course. Let us note, too, that while the south 



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