During the past few years reliable data on the speed of birds have accumulated slowly. It has been found that the common flying speed of ducks and geese is between 40 and 50 miles an hour, and that it is much less among smaller birds. Herons, hawks, horned larks, ravens, and shrikes, timed with the speedometer of an automobile, have been found to fly 22 to 28 miles an hour, while some of the flycatchers are such slow fliers that they attain only 1 to 17 miles an hour. Even such fast-flying birds as the mourning dove rarely exceed 35 miles an hour. All these birds can fly faster, but it is to be remembered that at training camps during the World War, airplanes having a maximum speed of about 80 miles an hour easily overtook flocks of ducks that it may be supposed were making every effort to escape. Aviators have claimed that at 65 miles an hour they can overtake the fastest ducks, though cases are on record of ducks passing airplanes that were making 55 miles an hour.
The greatest bird speeds that have been reliably recorded are of the swifts ([fig. 6]) and the duck hawk, or peregrine falcon (Falco peregrinus) ([fig. 7]). An observer in an airplane in Mesopotamia reported that swifts easily circled his ship when it was traveling at 68 miles an hour. To do this, the birds certainly were flying at a speed as high as 100 miles an hour. Once a hunting duck hawk, timed with a stop watch, was calculated to have attained a speed between 165 and 180 miles an hour.
The speed of migration, however, is quite different from that attained in forced flights for short distances. A sustained flight of 10 hours a day would carry herons, hawks, crows, and smaller birds from 100 to 250 miles, while ducks and geese might travel as much as 400 to 500 miles in the same period. Measured as air-line distances, these journeys are impressive and indicate that birds could cover the ordinary migration route from the northern United States or even from northern Canada to winter quarters in the West Indies or in Central America or South America in a relatively short time. It is probable that individual birds do make flights of the length indicated and that barn swallows (Hirundo erythrogaster) seen in May on Beata Island, off the southern coast of the Dominican Republic, may have reached that point after a nonstop flight of 350 miles across the Caribbean Sea from the coast of Venezuela. Nevertheless, whether they continue such journeys day after day is doubtful.
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Figure 6.—Chimney swift: a speedy day migrant, the flight, of which on occasions probably exceeds 100 miles an hour.
It seems more likely that migrations are performed in a leisurely manner, and that after a flight of a few hours the birds pause to feed and rest for 1 or several days, particularly if they find themselves in congenial surroundings. Some indication of this is found in the records of banded birds. Considering only the shortest intervals that have elapsed between banding in the North and recovery in southern regions, it is found that usually a month or more is taken to cover an air-line distance of a thousand miles. For example, a black duck (Anas rubripes) banded at Lake Scugog, Ontario, was killed 12 days later at Vicksburg, Miss. If the bird was taken shortly after its arrival, the record would indicate an average daily flight of only 83 miles, a distance that could have been covered in about 2 hours' flying time. Among the thousands of banding records obtained in recent years, evidences of such rapid flight are decidedly scarce, for with few exceptions all thousand-mile flights have required 2 to 4 weeks or more. The greatest speed thus far recorded for a banded bird is that of a mallard (A. platyrhynchos) banded on November 23, 1930, in Green Bay, Wis., and shot 5 days later, 900 miles away, near Georgetown, S. C. This bird doubtless flew at least 1,000 miles in the 5 days, as its route probably was not in a direct air-line, but, even so, the average daily distance was only 200 miles, which could easily have been covered in 5 hours.
It seems certain that migratory journeys are performed at the normal rate of flight, as this would best conserve the strength of the birds and eliminate the fatigue that would result from effort required for great speed. Migrating birds passing lightships and lighthouses, or crossing the face of the moon, have been observed to fly without hurry or evidence of straining to attain high speed.
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