72 OBSERVING BIRD-FLIGHT 



enough when the movements are compara- 

 tively slow, for there is then time to effect 

 them, but in the case of the bird there is no 

 time for a complicated movement, a double 

 action, as it were, at each succeeding wing- 

 beat. 



This principle, it seems to me, would 

 scarcely apply to a humming-bird, for exam- 

 ple, a bird that vibrates its wings with such 

 tapidity as to become invisible, and which, as 

 the name implies, produce a musical note. 

 The humming-bird's wing is modelled in the 

 same way as other birds, therefore we may 

 presume they are actuated in the same way, 

 only faster. 



As bird-flight can be witnessed at any 

 time, it is better to study it practically than 

 theorize about it. When flying, birds should 

 be watched from different points of view ; 

 from above, from underneath, laterally, and, 

 at the same time, as closely as may be. 

 Given, then, that all birds fly on the same 

 principle, if not in the same form, we shall do 

 well to mark the wing action of a slow flier, 

 in which case each stroke of the wing can be 

 distinctly seen. A heron, for instance, is a 

 slow mover, and, therefore, a good subject for 

 study in this respect, the only objection being 

 that the bird is wary and difficult of approach ; 



