164 



T/'owb/'idge — Interlocking of Emavginatt 



VI. Three well-defined Types of Flight in Raptores. 



Three distinct types of flight employed by birds of prey, 

 herons and various other large birds, are as follows : 



(1) Periodic wing beats ; in which for a part of the stroke 

 at least the primaries are fully extended. 



(2) Soaring (in circles) : in which the wing is widely extended 

 and the primaries may or may not be extended, depending on 

 conditions of wind, etc. 



(3) Coasting with set wings. In this case the primaries are 

 partly extended only, as shown in fig. 15. Diving through 

 the air differs only in degree from coasting but in this case 

 the wing is partly closed, the primaries nearly flexed and the 



tail often closed, steering being aided by the wings, as in fig. 

 16. Of course birds often combine these types, i. e., alternat- 

 ing periodically (1) and (2), or (1) and (3). Coasting flight is 

 one that is employed by Raptores, herons, gulls, etc., continu- 

 ally, both during their migrations and in their daily evolutions. 



