Birds. 7145 



Note on the supposed Occurrence of the Hirundo bicotor of North America in 

 England*— I venture to send for exhibition a skin of the North American Hirundo 

 hicolor of Vieillot, which was formerly the property of uiy late very good friend 

 Mr. John Wolley, and which there can be little doubt was obtained from a bird killed 

 in this country, though Mr. Wolley, with that admirable caution which distinguished 

 him in recording the reported occurrence (Zool. 3806), was careful to mention that 

 there was "a possibility of mistake" in the matter. I think that perhaps some 

 members of the Society will view this specimen with a certain amount of interest; but, 

 apart from this, my object in its exhibition is mainly to draw the attention of natu- 

 ralists to a matter which is every day becoming of greater consequence to those 

 ornithologists who chiefly occupy themselves with the Avi-fauna of any one district. 

 I refer to the occurrence within particular limits of stray examples of exotic species. 

 It is not only "British bird" students who find in these alien immigrants a great 

 cause of perplexity. To whatever country we go, we are, perhaps before we have well 

 ascertained the number of the bond fide species, puzzled by some wanderer turning up 

 exactly where he was least wauled. In my own opinion, the ornitliologist must 

 accept his position with all its responsibilities ; he chooses to study a class of beings, 

 some of whom, for all sublunary purposes at least, are blest with almost infinite powers 

 of locomotion. He must, therefore, not complain if in the course of a morning's walk 

 here in England, an Australian swift flies in his face, or he picks up a dead crossbill 

 of a Transatlantic species; and he must invoke no Deus ex machina in the shape of 

 an auxiliary -screw clipper or a careless aviary-keeper to account for the incident. 

 Facts like these hardly admit of a doubt, and force themselves day by day more and 

 more upon the notice of the thoughtful naturalist. For some time, indeed, European 

 ornithologists have been accustomed to regard the properly authenticated appearance 

 of an exotic species, which there may be good reason to suppose have reached our 

 shores without intentional human aid, as sufficient ground for including it in the list 

 of our birds. But as observers have of late so largely increased, so have these occur- 

 rences been more frequently noticed ; and it seems absolutely necessary to prescribe 

 some limit to prevent our really native species from being outnumbered by these 

 foreigners. The difficulty is to know where to draw tiie line; and to this point 

 I would invite the careful consideration of naturalists. It may be all very well to call 

 Thalassidroma Wilsoni and Mergus cucullalus European birds; but because a single 

 individual of Regulus calendulus or Dendrjeca virens has reached the Old World, it 

 is absurd to include either of those species in its Fauna. I cite these instances, be- 

 cause they are all from that continent whence most of our occasional visitants arrive ; 

 so much so, that one is almost driven to the conclusion that there is no prima facie 

 reason why examples of the greater number of birds of Eastern Nonh America should 

 I not, favente zephyro (the prevailing strong wind in Western Europe), make their ap- 

 I pearance on our shores in course of time. Then, on the other hand, the last two addi- 

 j tions to the list of so-called " British birds" have been from the opposite quarter. Are 

 I Syrrhaptes paradoxus and Xema ichthyaetus to take their places in the books eluci- 

 dating British Ornithology by the side of the red grouse and the peewit gull.? It 

 appears to me that we gain nothing by deferring a decision on the subject, and 



* From the ' Proceedings of the Zoological Society of London,' February 28, I860, 

 and obligingly communicated by the author. 



XVIII. 2 z 



