CHAPTER VI. 
THE CLASSIFICATION OF BIRDS. 
HE great multitude of Birds—of which upwards of eleven 
thousand kinds at the least are known to exist—makes it 
obviously necessary for those who would study them to arrange 
or classify them in groups. Otherwise the multitude of species 
would be too great for our powers of imagination and memory. 
The arrangement in groups, or Classification, of Birds, follows 
the principles which have been adopted in the classification of 
Animals generally. That system is one whereby creatures are 
sorted into a series of groups, successively smaller, and more 
and more subordinate. 
Animals, like plants, are, as we said at starting’, considered 
as members of one great group, which has been fancifully 
termed a “Kingdom ”—the Animal Kingdom containing all 
animals, as the 7 “egetable Kingdom contains all plants. The 
principles adopted by both zoologists and botanists in subdividing 
these “ Kingdoms” are “ morphological.” By this term it is 
meant that the characters upon which these classifications re- 
pose, and by which the various subordinate groups are defined, 
are characters taken from the shape, number, structure, and 
mutual relations of the parts of which the various creatures so 
classified are built up, and not upon what such parts do—the 
characters refer to “structure” not to “ function.” 
The kingdom of animals is divided into a variety of subking- 
doms, each of which is, of course, a very large group of animals 
indeed. Hach subkingdom is again divided into subordinate 
groups termed classes. Hach class is again divided into orders, 
and each order is further subdivided into families ; each family 
into genera, and each genus into spectes—a zoological species being 
“a group of living organisms which differ only by inconstant 
1 See ante, p. 3. 
