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 population 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 trans-gulf 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).
[Illustration: _Figure 25. Breeding range and migration routes of the Connecticut warbler. From the breeding range in northern United States and southern Canada, it migrates east in the fall to New England, then south along the Atlantic coast to Florida and across the West Indies to winter in South America. In the spring it does not return by the same route but rather completes a loop by migrating northwest across the Allegheny Mountains and the Mississippi Valley (Adapted from Cooke 1915a)._]