MIGRATIONS OF WATERFOWL 



In a long migration, like the 3,000 miles from the Mackenzie Delta to 

 the Gulf of Mexico, the relative values for man and Canvasback are : 



Velocity 

 (M.P.H.) 



Man 4 



Canvasback 60 



Travel 



Distance 



(Miles) 



200 



3,000 



Altitude 



of Travel 



(Feet) 



133.3 



2,000 



Breadth 



of Vision 



(Miles) 



30 



118 



Not all birds fly as high or as swiftly as waterfowl. In the Delta region, 

 for example, blackbirds average 30 m.p.h. at approximately 200 feet, and in 

 the table below a day's journey of 250 miles for a blackbird is compared 

 with a man's walk : 



Man 



The four dimensions of travel apply to all bird movement, but flight 

 does not always have a relative advantage over walking. Some small birds, 

 for example, are known to fly within three or four feet of the land or sea, 

 and the Penguin migrates with its eyes at sea level. 



The importance of the height and breadth of perception in travel is not 

 always understood. At an elevation of 5& feet, the eyes see a segment of 

 earth, bounded by the horizon, that is slightly more than 6 miles in diam- 

 eter. At an elevation of 2,000 feet the diameter between horizons is 118 

 miles. In terms of miles, the area encompassed by the horizon at 2,000 feet 

 is nearly 20 times as wide as the circle of vision at 5& feet. But the rela- 

 tive size of this earth circle is the same at both (and at all) elevations. The 

 validity of this may be tested by pointing a finger at the horizon, which is 

 always at eye level, regardless of altitude. No matter if one stands on the 

 ground or in an airliner at 2,000 feet, the arc of vision between finger and 

 feet is the same. The universe is divided into earth and sky at the horizon, 

 and the proportion of the traveler's vision that includes the earth is constant 

 regardless of his elevation, the relative size of the world remaining un- 

 changed throughout travel. 



We know, of course, that the higher one rises, the farther one sees. This 

 extension of vision results from a relative shrinking of the earth's dimen- 

 sions. As one goes up, the miles decrease in relative size as more miles come 



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