March. When these golden plovers leave their winter quarters they 

 cross northwestern South America and the Gulf of Mexico to reach 

 the North American mainland on the coasts of Texas and Louisiana. 

 Thence they proceed slowly up the Mississippi Valley and, by the 

 early part of June, are again on their breeding grounds, having 

 performed a round-trip journey in the form of an enormous ellipse 

 with the minor axis about 2,000 miles and the major axis 8,000 miles 

 stretching from the Arctic tundra to the pampas of Argentina. The 

 older birds may be accompanied by some of the young, but most of the 

 immature birds leave their natal grounds late in summer and move 

 southward through the interior of the country, returning in spring 

 over essentially the same course. The oceanic route is therefore used 

 chiefly by adult birds. 



A return by the oceanic route in the spring could be fatal. The 

 maritime climate in the Northeast results in foggy conditions along 

 the coast and the frozen soil would offer few rewards for the weary 

 travelers. By traveling up the middle of the continent, a much better 

 food supply is assured (Welty 1962). 



Several North American warblers including the Connecticut 

 warbler (Fig. 25) and the western race of the palm warbler have been 

 found to follow circuitous migration routes. The Connecticut warbler 

 is not observed or banded on the East coast in spring, but it is 

 recorded farther inland during the season. Thus this warbler 

 proceeds down the East coast in the fall and up the interior of the 

 continent in the spring. Similarly, the western race of the palm 

 warbler moves from its breeding grounds directly east to the 

 Appalachian Mountains before turning south along the coast. 

 Television tower kills in northern Florida indicate the population is 

 very concentrated here at this time of year. In the spring this race 

 also proceeds north through the interior. Graber (1968) points out 

 that the eastern race of the palm warbler also proceeds south along 

 the coast in the fall and poses this question: "does the western popula- 

 tion of this species intentionally move toward the ancestral range, or 

 is the fall flight direction merely a consequence of the temperate zone 

 westerly circulation?" 



Graber concluded from radar observations that the disparity in 

 seasonal flight directions of many migrants was a positive response of 

 migrants to favorable wind directions at that time of year. The east- 

 oriented transgulf migrants followed an elliptical migration because 

 postfrontal air flow in the fall at latitude 40 N is northwesterly, and, 

 in the spring southerly; whereas winds over the Gulf of Mexico are 

 consistently easterly or southeasterly. Therefore, transgulf migrants 

 returning north in the spring would be moved westward across the 

 Gulf unless they compensated for wind drift. Observers were not 

 aware of high-altitude drift before radar (Bellrose and Graber 1963). 



Numerous other loop migrations have been documented through- 

 out the world. In the fall, the short-tailed shearwater, is observed off 

 the west coast of North America as far south as California. At this 

 time the species is on the eastern leg of a tremendous figure-eight 



84 



