THE RELATION OF WIND TO BIRD MIGRATION, 
C. C. TROWBRIDGE. 
THE influence of meteorological conditions on the migra- 
tion of birds has been studied by a number of observers. 
Among the important monographs on the subject is that of 
Prof. W. W. Cooke, “Bird Migration in the Mississippi Val- 
ley," in which it is shown clearly that migratory waves of 
birds accompany changes of temperature. The wind direc- 
tions and velocities were recorded in the paper mentioned but 
the author did not regard the migratory movements to be due 
to the direct effect of the wind, which was considered merely 
as the chief cause of the temperature changes. 
The same view is held by Dr. W. Stone in his “Birds of 
Eastern Pennsylvania and New Jersey," in which by a series 
of curves the fact is illustrated that migratory waves of birds 
follow closely changes of temperature. 
The author of the present paper believes that the bird waves 
described by the above observers were largely due to the direct 
influence of favorable winds, and that the wind is a more impor- 
tant factor in bird migration than it is generally regarded. 
That the subject has not received much attention is shown 
-by the recent valuable review on bird migration by Dr. F. H. 
Knowlton in Popular Science Monthly» In the paper referred 
to no mention of the relation of the wind to bird migration is - 
made. In fact, the word “wind” is not used in the thirteen 
pages of the article. 
In considering the relation of meteorology to bird migra- 
tion, general as well as local atmospheric conditions must be 
studied, and it is important that the atmospheric conditions 
Where the birds start on their migratory journeys be deter- 
mined, if possible. Furthermore, the number of new arrivals 
! Knowlton, Dr. F. H. The Journeyings of Birds, Pop. Sci. Mon., vol. 1x, 
No. 4, p. 323. 
735 
