No. 429.] RELATION OF WIND TO BIRD MIGRATION. 737 
subsequent observations. The cause of the flights was stated 
to be as follows: 
Hawks drift with the wind when soaring, 
continually, their movements during migrations are largely 
dependent on the direction of the wind. In the present case 
hawks migrating in autumn in New England drift south or 
and as they soar 



WIND N.W. b 

^w, 

Mar I.— Coast LINE oF THE NEW ENGLAND STATES AND NEW JERSEY. 
The long arrows indicate the general direction of migration of hawks and many other land 
d ng why these birds congregate 
vente | in the autumn, when de wind is northwest, illustratin 

The peces circles drawn about a point off the comet of Maine are low-p isobars indi 
causing the inds over ipe: north- 
pea hawks f ollow a narrow path and 
g higher as the id becomes 


enstern part of the United States. 
low; at B the hawks gradually separate, es 
more favorable. 
