Page:Popular Science Monthly Volume 60.djvu/337

Rh Singly or in groups, large and small, or more seldom in a great throng, the hurrying myriads pressed southward."

The second station chosen by Mr. Libby was the Washburn Observatory, where for three nights he watched the birds passing across the face of the moon. During the three nights a total of 583 birds were counted, the largest number in any fifteen-minute period being 45. Considerable diversity in the direction of flight was noted. Thus up to ten o'clock the prevailing direction was south, but after this time the diversity increased, until it reached its maximum between twelve and two o'clock, when eight principal points of the compass were represented by numbers varying from 3 to 28. However, two-thirds of the number were still maintaining a southerly direction.

Libby attempted to estimate roughly the total number of birds that passed his point of observation during the three nights, but as he well says, 'when one recalls the relatively small size of the moon's surface as compared to its path from east to west, within the range of vision,' the difficulty becomes evident. As nearly as could be made out about 9,000 birds were passing per hour or a grand total of 168,000.

The rate of speed at which birds travel during the migrations, and also at other times, has been made the subject of observation, although the results, as might be expected from the confusing elements which must enter into such an inquiry, are far from complete or satisfactory. If the speed often attained by powerful and swift-flying species, such as ducks, geese, swallows, etc., could be maintained, it is obvious that the time occupied in migrations would be inconsiderable. But, as will be shown later, the maximum speed appears to be rarely or never realized at this time.

Frank Forrester records 90 miles an hour for ducks, as noted by telegraph from point to point, and an albatross has been known to cover 3,150 miles in 12 days. The actual distance flown by the latter bird was probably at least twice as great, for they rarely fly far in a straight line.

Some years ago Griffitt made some observations (recorded in 'The Field,' Feb. 19, 1887) in a closed gallery on the speed attained by 'blue-rock' pigeons and English pheasants and partridges. The two first mentioned flew at the rate of only 32.8 miles per hour, while the partridge made but 28.4 miles, and these rates were all considerably in excess of what they made in the open. The carrier pigeon is a rather fast flying bird, yet the average speed is not very great. Thus the average made in 18 matches ('The Field,' Jan. 22, 1887) was only 36 English miles an hour, although in two of these trials a speed of about 55 miles was maintained for 4 successive hours. In this country the average racing speed is apparently about 35 miles an hour, although a few exceptionally rapid birds have made short distance flight at the