228 
CoL It. Meinertzhagen on the 
[Ibis, 
XII .—-Some 'preliminary remarks on the Velocity of Migratory 
Flight among Birds, with special reference to the Palee- 
arctic Region. By Colonel It. Meinertzhagen, D.S.O., 
F.Z.S." 
The question arises at once as to whether migratory flight 
is of a different nature to daily flight in search of food or to 
escape enemies. We have some interesting opinions on this 
subject. Gatke tells us that the speed of birds during 
their daily locomotions in the air has not an approximate 
relation to the wonderful velocity of flight attained by them 
during their migrations. He accounts for such enormous 
speed by the fact that birds migrate in the more elevated 
layers of the atmosphere, in which more uniform conditions 
prevail, and which are less subject to powerful meteorological 
disturbances. 
Cooke (‘ Bird Migration ’), on the other hand, thinks that 
migrating birds do not fly at their fastest. He believes that 
their migrating speed is usually from 30 to 40 miles an hour, 
and rarely exceeds 50. Flights of a few hours at night, 
alternating with rests of one or more days, make the spring 
advance very slow. He goes on to say that during day- 
migration the smaller land-birds seldom fly faster than 
20 miles per hour, though larger birds move somewhat 
more rapidly. 
I believe Gatke’s theory to be based on faulty evidence, 
as I hope to show later. Moreover, birds would experience 
greater difficulties in flying in the u more elevated layers of 
the atmosphere, 5 ’ as the atmosphere is rarer and therefore 
offers a less suitable mixture on which their wings can beat. 
They would experience the same difficulties as a man trying 
to swim in froth. 
My own observations tend to show that migratory flight 
differs very little in its velocity from the flight of daily move¬ 
ment, and I see no reason why it should or how it can be so. 
I believe migratory flight to be steady and unhurried, and 
