MUSCICAPIKE. 109 



tainly none more inexplicable, than that certain 

 groups of birds, having a limited geographic distri- 

 bution, should be distinguished from others of the 

 same family (but inhabiting another continent), by 

 a slight but invariable deviation in ^the form of their 

 wings. This difference might be accounted for, if, 

 upon further investigation, we had found that it was 

 accompanied by a difference in the mode of flying 

 or of capturing the food. But hitherto not the 

 slightest variation has been detected, on these 

 points, between the fly-catchers (Muscicapa) of 

 the Old World and those of America. Neverthe- 

 less, so decidedly different is the structure of the 

 wing in these two great geographic groups, that we 

 may at once decide from this circumstance alone, 

 whether a species we see for the first time is a New 

 or an Old World fly-catcher. We drew the atten- 

 tion of ornithologists to this remarkable fact some 

 years ago*, and subsequent experience has not fur- 

 nished us with a single exception to the rule. The 

 common grey fly- catcher of Britain catches its prey 

 in precisely the same manner, so far as 1 can dis- 

 cover, as do the little tyrants (Tyrannula) of Bra- 

 zil, both sit upon a twig, dart at passing insects, and 

 return to the same station ; but the European 

 species has the first quill-feather so small as to be 

 spurious, or as it were elementary, while that of the 

 other is three times as long, and the proportions of 



* Northern Zoology. 



