FLIGHT SPEED OF BIRDS 5 



course at a great rate of speed as though the force of the wind made 

 little difference to them. Many incidents have been recorded of birds 

 on migration that apparently waited for a favorable wind to help 

 them on their way; or, at any rate, until an adverse one was past. 



It is popularly supposed that birds in migration climb until they 

 find a favoring wind, sometimes to great altitudes. Aviators report 

 that it is exceptional to see any birds more than 5,000 feet above the 

 earth and that few are seen above 3,000 feet. There are, however, 

 records of birds seen at very high altitudes above sea level, but these 

 are mostly in mountainous country where the birds are flying at 

 comparatively short distances above the land. Under normal weather 

 conditions some species regularly fly low, whereas others invariably 

 fly high; in bad weather most birds fly low, as shown by their striking 

 against lighthouses and high buildings. 



The evidence thus far obtained indicates that the greater part of 

 migration takes place below 3,000 feet above the earth's surface, 

 much of it below 1,000 feet, and that birds prefer to fly below the level 

 of the clouds. The definite observations are of daytime migrations, 

 but there is no reason to suppose that birds fly any higher by night 

 than by day. Furthermore, what man considers a favoring wind 

 may not be chosen by the birds. An aviator (56) tells of flying with a 

 large flock of lapwings in northern France at an altitude of 5,500 feet. 

 The birds were flying due north into a strong wind at an air speed of 

 about 50 miles an hour but were not making more than 20 miles an 

 hour headway, while on the ground the wind was from the south at 

 about 5 miles an hour, and at 3,000 feet it was northwest at a little 

 over 30. 



Birds on migration must take the rate of speed that can be main- 

 tained for the longest time with the greatest economy of effort. On 

 occasion, however, most birds can considerably increase this speed. 

 Meinertzhagen (49), as a result of his study of the available informa- 

 tion, came to the conclusion that — 



birds have two speeds — a normal rate which is used for everyday purposes and 

 also for migration, and an accelerated speed which is used for protection or pur- 

 suit, and which in some cases nearly doubles the rate of their normal speed. 



Since his paper was published in 1921, many additional data have 

 been gathered, especially relative to the song and insectivorous species. 

 From these it seems that the short daily flights are subject to much 

 variation in speed but are often quite slow and that the flight of birds 

 coming to their roosts toward evening is faster and seems to be com- 

 parable with that used in migration. 



TABLE OF SPEEDS 



In table 1 are given all the speed-of -flight records at hand of North 

 American species and also of a few European species that have oc- 

 curred in North America and are included because the birds are closely 

 related to North American species for which no records are available. 

 A few running speeds are added as a matter of interest. The species 

 are arranged in the order of the American Ornithologists' Union 

 Check List of North American Birds (4th ed. 1931). The source of 

 all the material summarized in the table is given in the bibliography, 

 with the exception of the few items in which the authors' names are 

 followed by initials, which are manuscript records of the Biological 

 Survey. 



