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 wimbrill ( S. 
phceopus ) 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; becaiise the black crow in- 
habits New Holland and seems to fly and cam 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; w'hereas it is strictly con- 
fined to the latter continent, although represented 
by other species in widely separated regions. For 
