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Migration of Birds (1950)

Chapter 31: Arctic routes
By Frederick Charles Lincoln
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Environmental IssuesNature/Gardening/AnimalsScience - Biology

About This Book

A comprehensive survey explains why and how many bird species undertake seasonal movements, reviewing historical observations and competing ideas on origins and control, including ancestral-range shifts, photoperiodic cues, and continental changes. It outlines when and how birds travel, contrasting nocturnal and diurnal movements and detailing flight speeds, typical altitudes, navigation methods, and segregation by age or sex. Geographic coverage ranges from short local shifts to long-distance migrations and includes continental flyways, coastal and oceanic routes, vertical movements, and occasional vagrancy. The work examines hazards such as storms, exhaustion, and man-made obstacles, summarizes banding and observational studies, and highlights implications for conservation and management.

Figure 22.—Migration of the western tanager. The birds that arrive in eastern Alberta by May 20 do not travel northward along the eastern base of the Rocky Mountains, as in that region the van has then only reached northern Colorado. Instead the isochronal lines indicate that they migrate north through California, Oregon, and Washington, and then cross the mountains of British Columbia.

The Pacific oceanic route probably is used also by the arctic terns that breed in Alaska, and possibly by those from the more western tern colonies of Canada. This species is of regular occurrence on the western coasts of both the United States and South America, indicating that the western representatives travel southward to the Antarctic winter quarters without the spectacular migration features that appear to characterize the flight of those from the eastern part of the continent (fig. 8).

Arctic routes

In the discussion of the migration of the Arctic tern (p. 38) it was noted that this species makes a very distinct west-to-east movement across northern Canada, continuing the flight eastward across the Atlantic Ocean toward the western coast of Europe. It seems likely that there are other species, including the parasitic jaeger, that regularly breed in the northern part of the Western Hemisphere but migrate back to the Old World for their winter sojourn. Some others, as the red-legged kittiwake and Ross's gull, remain near the Arctic region throughout the year, retreating southward in winter only a few hundred miles. The emperor goose in winter is found only a relatively short distance south of its breeding grounds, and eider ducks, although wintering in latitudes well south of their nesting areas, nevertheless remain farther north than do the majority of other species of ducks.

The routes followed by these birds are chiefly coastwise, and in the final analysis may be considered as being tributary either to the Atlantic or to the Pacific coast routes. The passage of gulls, ducks, the black brant, and other water birds at Point Barrow, Alaska, and at other points on the Arctic coast, has been noted by several observers, and from present knowledge it may be said that the best defined Arctic route in North America is the one that follows around the coast of Alaska.

Figure 23.—Distribution and migration of the red-eyed vireo. It is evident that the red-eyed vireo has only recently invaded Washington by an extension of its breeding range almost due west from the upper Missouri Valley. Like the bobolink, however (fig. 19), the western breeders do not take the short cut south or southeast from their nesting grounds, but migrate spring and fall along the route traveled in making this extension.