Figure 6. The "duffer's course." 

 Here the bird aims its body always 

 toward the objective. Flight path 

 "A" shows the duffer's course when 

 a bird with a 40 m.p.h. air speed 

 flies against a quartering wind of 

 28 m.p.h. In flight path "B" the 

 bird crosses a 28 m.p.h. wind, while 

 in flight path "C" the bird is fa- 

 vored by a 28 m.p.h. wind quar- 

 tering from behind. The birds shown 

 on each of the flight paths have 

 flown an equal time interval, the 

 bird of flight path "C" having nearly 

 reached its objective, the bird of 

 flight path "A" having gone only 

 a third of the way. With no wind 

 at all, the flight path would be a 

 straight line from start to finish. 



to the next in cross-country travel. At Delta I have seen this not only in 

 blackbirds, but in Blue-winged Teal flying along the edge of Cadham Bay 

 in a series of curves from one point of reeds to the next. One sees ducks 

 following the duffer's course when they come in to the decoys, and this 

 technique is often used in making landings either on water or ashore. When 

 a bird has been flying with the wind from behind, it frequently adopts the 

 duffer's course as it turns to make its landing into the wind. 



When the speed of the wind is greater than a bird's air speed, forward 

 motion over the ground is impossible. More than once I have seen Mallards 

 hanging for several seconds in mid-air when meeting the strong lake breeze 

 pouring into the mouth of the Delta channel. I have watched Canada Geese 



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