Another example of this "leap-frog" migration is illustrated by the common yellowthroat of the Atlantic coast. Birds occupying the most southern part of the general range are almost nonmigratory and reside throughout the year in Florida, whereas the population that breeds as far north as Newfoundland goes to the West Indies for the winter. Thus the northern population literally "jumps" over the home of the southern relatives during migratory journeys.
The palm warbler breeds from Nova Scotia and Maine west and northwest to southern Mackenzie. The species has been separated into two subspecies: those breeding in the interior of Canada and those breeding in northeastern United States and Canada. The northwestern subspecies makes a 3,000-mile journey from Great Slave Lake to Cuba and passes through the Gulf States early in October. After the bulk of these birds have passed, the eastern subspecies, whose migratory journey is about half as long, drifts slowly into the Gulf Coast region and remains for the winter.
Fall Flights Not Far South of Breeding Range
Some species have extensive summer ranges (e.g., the pine warbler, rock wren, field sparrow, loggerhead shrike, and black-headed grosbeak) and concentrate during the winter season in the southern part of the breeding range or occupy additional territory only a short distance farther south. The entire species may thus be confined within a restricted area during winter, but with the return of warmer weather, the species spreads out to reoccupy the much larger summer range.
[Illustration: _Figure 10. Migration of Pacific coast forms of the fox sparrow. The breeding ranges of the different races are encircled by solid lines, while the winter ranges are dotted. The numbers indicate the areas used by the different subspecies as follows: L Shumagin fox sparrow; 2. Kodiak fox sparrow; 3. Valdez fox sparrow; 4. Yakutat fox sparrow; 5. Townsend fox sparrow; 6. sooty fox sparrow (After Swarth 1920)._]
Many species, including the tree sparrow, snow bunting, and Lapland longspur, nest in the far north and winter in the eastern United States, while others, including the vesper and chipping sparrows, common grackle, red-winged blackbird, eastern bluebird, American woodcock, and several species of ducks, nest much farther south in the United States and Canada and move south a relatively short distance for the winter to areas along the Gulf of Mexico. In a few of the more hardy species, individuals may linger in protected places well within reach of severe cold. The common snipe, for example, is frequently found during subzero weather in parts of the Rocky Mountain region where warm springs assure a food supply. More than 100 summer birds leave the United States entirely and spend the winter in the West Indies, Central America, or South America. For example, the Cape May warbler breeds from northern New England, northern Michigan, and northern Minnesota, north to New Brunswick, Nova Scotia, and nearly to Great Slave Lake. In winter it is concentrated chiefly in the West Indies on the island of Hispaniola.