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THE MIGRATION OF NORTH AMERICAN BIRDS 1o 
and published thereon in 1891 (21). He postulated that the blue- 
throat (Cyanosylvia suecica), a species of thrush smaller than the 
American hermit thrush, would leave African winter quarters at dusk 
and reach Heligoland at dawn, which would mean a sustained speed 
of 200 miles an hour; and that the American golden plover (Pluvialis 
dominica) flew from the coast of Labrador to Brazil in 15 hours, or at 
the tremendous speed of 250 miles per hour. These conclusions are 
now considered unwarranted by most ornithologists. 
Sportsmen also often greatly overestimate the speed at which ducks 
and geese fly and sometimes attempt to substantiate their estimates 
by mathematical calculations, based upon the known velocity of a 
charge of shot, the estimated distance, and the estimated “‘lead”’ that 
was necessary to hit the bird. If all three elements of the equation 
were known with certainty, the speed of the bird could be determined 
with a fair degree of accuracy. The majority of the ducks that are 
reported as killed at 40, 50, or even 60 yards, however, actually are 
shot at distances much less than estimated. To sight along a 
gun barrel and estimate correctly the distance of a moving object 
against the sky is so nearly impossible for the average gunner as to 
make such calculations of little value. 
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 10 to 17 milesan hour. Evensuch 
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 train- 
ing 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 pere- 
grinus) (fig. 7). An observer in an airplane in Mesopotamia re- 
ported that swifts easily circled his ship when it was traveling at 68 
milesan 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 at- 
tained 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 ordi- 
nary 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, 
