314 
SPECIES OF BIRDS. 
atricapilla , or blackcap, Sylvia garrula of Bechstein, 
and also with species of Troglodytes and Perdrix. 
They shew such marked differences, that we can 
determine them with ease after a little practice. The 
principal differences are here again in the head and 
bill. It has been ascertained, that different forms of 
crania determine different species of mammalia, but that 
the determinations are less strikingly marked in the 
smaller animals, as those of the mouse, shrew, and bat 
tribes, than in the larger ones, but that, in all these, the 
teeth afford good distinctive characters. It is worthy 
of remark, that, as the bill in birds is equivalent to the 
teeth in quadrupeds, that differences in the manducatory 
organs, in both classes, afford specific characters. 
Many ornithologists, says Brehm, will consider these 
distinctions either as useless, or as leading to needless 
minutiae,-— an opinion he considers as erroneous. In 
illustration of the importance of such distinctions, he 
remarks, that the very precise determination of the species 
of birds affords interesting disclosures in regard to their 
migrations. Hitherto, says he, it has been believed that 
the Strix bubo , or great horned owl, Cinclus , or water 
rail, wild duck, (Anas boschas ,) Regulus , or gold-crested 
wren, and many others, remained in his neighbourhood, 
(Renthendorf,) during the winter, which is not the 
case ; for accurate determination of the species has 
shewn, that their great-horned owl leaves them, and its 
place is taken in the winter season by that from the 
north ; that a kind of wild duck, which rarely breeds 
in Central Germany, but is a native of the Faro Islands, 
is common in the open brooks and rivers in the winter 
season ; that the Northern Cinclus occurs more fre- 
quently in winter in their mountains, streams, and 
brooks, than the German Cinclus ; and that it is rarely 
the case that the gold-crested wren, which breeds there, 
remains over the winter, its place being taken by the 
northern species, which has wandered to them across 
the Baltic. 
These facts, (allowing Brehm’s determinations to be 
correct,) shew, in a very interesting manner, the impor- 
