Northern Prairie Wildlife Research Center
Aristotle, naturalist and philosopher of ancient Greece, was one of the first observers whose writings are known to discuss the subject of bird migration. He noted cranes traveled from the steppes of Scythia to the marshes at the headwaters of the Nile, and pelicans, geese, swans, rails, doves, and many other birds likewise passed to warmer regions to spend the winter. Pliny the Elder, a Roman naturalist, in his "Historia Naturalis," repeated much of what Aristotle had written on migration and added comments of his own concerning the movements of European species of starlings, thrushes, and blackbirds.
Aristotle also must be credited with the origin of some superstitious beliefs that persisted for several centuries. One of these, that birds hibernated, became so firmly rooted that the eminent nineteenth century American ornithologist, Dr. Elliott Coues, listed in 1878 the titles of no less than 182 papers dealing with the hibernation of swallows. The students of Aristotle believed the disappearance of many species of birds in the fall was accounted for by their passing into a torpid state where they remained during the cold season, hidden in hollow trees, eaves, or in the mud of marshes. Aristotle ascribed hibernation not only to swallows, but also to storks, kites, and doves. Some early naturalists wrote fantastic accounts of flocks of swallows allegedly seen congregating in marshes until their accumulated weight bent the reeds into the water, submerging the birds, which apparently then settled down for a long winter's nap. It was even recorded that when fishermen in northern waters drew up their nets they sometimes had a mixed catch of fish and hibernating swallows. Olaus Magnus, Archbishop of Upsala, published a work in 1555 entitled "Historia de Gentibus Septentrionalis et Natura" observing that if swallows so caught were taken into a warm room they would soon begin to fly about but would live only a short time.
The idea of hibernation as a regular method of spending the winter is no longer broadly accepted for birds, although the Common Poorwill is a possible exception. Many species, however, such as chickadees, swallows, hummingbirds, swifts, and nightjars regularly go into torpor under cold stress on winter nights but also even during the breeding season.
Aristotle also was the originator of the theory of transmutation, the seasonal change of one species into another. Frequently one species would arrive from the north just as another species departed for more southerly latitudes. From this he reasoned the two different species were actually one and assumed different plumages to correspond to the summer and winter seasons.
Probably the most remarkable theory advanced to account for migration is contained in a pamphlet titled, "An Essay toward the Probable Solution of this Question: Whence come the Stork and the Turtledove, the Crane, and the Swallow, when they Know and Observe the Appointed Time of their Coming," published in 1703. It is written "By a Person of Learning and Piety," whose "probable solution" stated migratory birds flew to the moon and there spent the winter.
Some people who easily accepted the migratory travels of larger birds were unable to understand how smaller species, some of them notoriously poor flyers, could make similar journeys. They accordingly conceived the idea that larger species (e.g., storks and cranes) carried their smaller companions as living freight. In some southern European countries, it is still believed these broad-pinioned birds serve as aerial transports for hosts of small birds that congregate upon the Mediterranean shore awaiting the opportunity for passage to winter homes in Africa. Similar beliefs, such as hummingbirds riding on the backs of geese, have been found among some tribes of Native Americans in the Western Hemisphere. Such fantasies, however, are not without some empirical basis, such as the observation of an Eastern Kingbird harassing a Great Horned Owl that actually perched on the shoulder of the owl's outstretched wing as the owl glided toward wooded cover.
Today we realize that birds do not migrate by "hitching" rides with other birds and that the scope of the migration phenomenon is worldwide, not simply limited to the Northern Hemisphere or the world's land masses. The migration heritage is developed just as extensively in Old World warblers migrating to and from Europe and Africa as in our wood warblers traveling from Canada and the United States to South America and back. Although South Temperate Zone species migrate northward to the tropics during the austral winter, no land species nesting in the South Temperate Zone migrates into the North Temperate Zone. Some seabirds like the Sooty Shearwater and Wilson's Storm-petrel, however, migrate to North Temperate seas after nesting on shores south of the equator.