INTRODUCTION. 89 



in other birds. It is singular, that although nearly 

 all our different species of ducks are found likewise 

 in temperate America, not one has yet been dis- 

 covered further south than the lakes of Mexico, 

 while those of Brazil are totally unknown to the 

 northward of the isthmus of Darien. The waders, 

 forming the grallatorial order, are the most widely 

 dispersed of all birds, for several of those found in 

 Europe occur on the shores of India, North America, 

 and Western Africa; and if our naturalists have 

 not been deceived, our well known winabrill ( S. 

 phwopus) is actually the same on the shores of New 

 Holland. Such examples, however, of cosmopolite 

 birds are exceedingly rare ; it must be remembered 

 also that in a circle extremes meet; and as this 

 disposition is equally apparent in the geographic 

 distribution of animals, as in their natural classi- 

 fication, so we may reasonably expect that the two 

 polar regions of our globe would contain some 

 species common to both. The accounts, however, 

 of travellers, who are not themselves naturalists, 

 and even those which are found in many of our sys- 

 tematic works, must be received in many instances 

 with great suspicion; because the black crow in- 

 habits New Holland and seems to fly and caw like 

 our own, it has been set down as the same species. 

 The little gold-crest, Sylvia regulus, in like manner 

 is asserted to inhabit America and a number of 

 places out of Europe; whereas it is strictly con- 

 fined to the latter continent, although represented 

 by other species in widely separated regions. For 



