Dog-legs 



Dog-leg migration patterns are characterized by a prominent bend 

 or twist in the route. Studies have shown some of these illogical, out- 

 of-the-way means for connecting wintering and breeding areas have 

 no biological function, but instead, are the result of tradition much 

 like the lineage of crooked streets in Boston can be traced back to old 

 cowpaths (Welty 1962). Many species have extended their range in 

 recent years, but the pioneers continue to retrace the old route from 

 the point of origin even if the new areas are not on the same axis as the 

 earlier route. The old pathways have apparently become implanted 

 as part of the migratory instinct in all members of particular 

 populations even after extending their ranges considerable distances 

 from the original. 



Good examples of this crooked traditional path can be seen in the 

 routes taken by Old World species extending their ranges into the 

 New World from Europe and Asia. The European wheatear has 

 extended its range into Greenland and Labrador where the local 

 breeding population has become a separate race. When the Labrador 

 individuals depart from their breeding grounds, they proceed north 

 to Greenland, their ancestral home, then west to Europe and south to 

 Africa, the traditional wintering area for all wheatears. Alaskan 

 breeding wheatears migrate to Africa in the opposite direction via 

 Asia where the Alaskan population presumably originated. Alaskan 

 breeding Arctic and willow warblers and bluethroats also migrate 

 westward into Siberia and then southward on the Asiatic side. Some 

 investigators believe the Arctic tern colonized the New World from 

 Europe because when this bird departs for the south it first crosses 

 the Atlantic to Europe, then moves down the eastern Atlantic coast to 

 Africa and either back across the Atlantic to South America or 

 continues south down past South Africa (Fig. 11). To get to South 

 America from the eastern Arctic, it would be shorter to follow the 

 golden plover's flight path straight down the Atlantic or along the 

 east coast of the United States but the fact that no Arctic terns have 

 been observed in the Caribbean indicates that they do no follow that 

 route. 



In western United States, California gulls nest in various colonies 

 around Great Salt Lake and Yellowstone Park. Banding records 

 indicate these populations winter along the California coast (Fig. 27). 

 Instead of traveling southwest by the shortest distance to the 

 wintering grounds, they proceed longitudinally down the Snake and 

 Columbia Rivers and reach the coast around Vancouver ( Woodbury 

 et al. 1946). Thence they proceed south along the coast to Oregon and 

 California. In the spring the adults return over the same course 

 rather than taking the shorter flight northeast in April across the 

 deserts and mountains; this route would be largely made over a cold 

 and inhospitable country (Oldaker 1961). 



Sladen (1973) has mapped the migration routes of whistling swans, 

 and several dog-leg patterns are apparent in the eastern and western 



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