IV 
HUMMING-BIRDS 
AS ILLUSTRATING THE LUXURIANCE OF TROPICAL NATURE 
Structure—Colours and Ornaments—Descriptive Names—The Motions 
and Habits of Humming-birds—Display of Ornaments by the Male— 
Food—Nests—Geographical Distribution and Variation—Humming- 
birds of Juan Fernandez as illustrating Variation and Natural Selec- 
tion—The Relations and Affinities of Humming-birds—How to Deter- 
mine doubtful A ffinities—Resemblances of Swifts and Humming-birds 
—Differences between Sun-birds and Humming-birds—Conclusion. 
THERE are now about ten thousand different kinds of birds 
known to naturalists, and these are classed in one hundred 
and thirty families, which vary greatly in extent, some con- 
taining a single species only, while others comprise many 
hundreds. The two largest families are those of the warblers, 
with more than six hundred, and the finches with more than 
five hundred species, spread over the whole globe; the hawks 
and the pigeons, also spread over the whole globe, number 
about three hundred and thirty and three hundred and sixty 
species respectively ; while the diminutive humming-birds, 
confined to one hemisphere, consist of about four hundred 
different species. They are thus, as regards the number of 
distinct kinds collected in a limited area, the most remarkable 
of all the families of birds. It may, however, very reasonably 
be asked, whether the four hundred species of humming-birds 
above alluded to are really all distinct—as distinct on the 
average as the ten thousand species of birds are from each 
other. We reply that they certainly are perfectly distinct 
species, which never intermingle ; and their differences do not 
consist in colour only, but in peculiarities of form, of structure, 
