The group of birds usually known as the _Raptores_, or Rapacious Birds,
embraces three well-marked divisions, namely, the Owls, the Hawks,
and the Vultures. In former classifications they headed the Class of
Birds, being honored with this position in consequence of their powerful
organization, large size, and predatory habits. But it being now known
that in structure they are less perfectly organized than the _Passeres_
and _Strisores_, birds generally far more delicate in organization,
as well as smaller in size, they occupy a place in the more recent
arrangements nearly at the end of the Terrestrial forms.
The complete definition of the order _Raptores_, and of its
subdivisions, requires the enumeration of a great many characters; and
that their distinguishing features may be more easily recognized by
the student, I give first a brief diagnosis, including their simplest
characters, to be followed by a more detailed account hereafter.
COMMON CHARACTERS. Bill hooked, the upper mandible furnished at the base
with a soft skin, or “cere,” in which the nostrils are situated. Toes,
three before and one behind. _Raptores._
=Strigidæ.= Eyes directed forwards, and surrounded by radiating
feathers, which are bounded, except anteriorly, by a circle or rim of
differently formed, stiffer feathers. Outer toe reversible. Claws much
hooked and very sharp. Legs and toes usually feathered, or, at least,
coated with bristles. _The Owls._
=Falconidæ.= Eyes lateral, and not surrounded by radiating feathers.
Outer toe not reversible (except in _Pandion_). Claws usually hooked
and sharp, but variable. Head more or less completely feathered. _The
Hawks._
=Cathartidæ.= Eyes lateral; whole head naked. Outer toe not
reversible; claws slightly curved, blunt. _The Vultures._
The preceding characters, though purely artificial, may nevertheless
serve to distinguish the three families of _Raptores_ belonging to
the North American _Ornis_; a more scientific diagnosis, embracing
a sufficient number of osteological, and accompanying anatomical
characters, will be found further on.
The birds of prey—named _Accipitres_ by some authors, and _Raptores_
or _Rapaces_ by others, and very appropriately designated as the
_Ætomorphæ_ by Professor Huxley—form one of the most strongly
characterized and sharply limited of the higher divisions of the Class
of Birds. It is only recently, however, that their place in a systematic
classification and the proper number and relation of their subdivisions
have been properly understood. Professor Huxley’s views will probably
form the basis for a permanent classification, as they certainly point
the way to one eminently natural. In his important paper entitled
“On the Classification of Birds, and on the Taxonomic Value of the
Modifications of certain Cranial Bones observable in that Class,”[2]
this gentleman has dealt concisely upon the affinities of the order
_Raptores_, and the distinguishing features of its subdivisions. In the
following diagnoses the osteological characters are mainly borrowed
from Professor Huxley’s work referred to. Nitzsch’s “Pterylography”[3]
supplies such characters as are afforded by the plumage, most of which
confirm the arrangement based upon the osteological structure; while
important suggestions have been derived from McGillivray’s “History of
British Birds.”[4] The Monographs of the _Strigidæ_ and _Falconidæ_, by
Dr. J. J. Kaup,[5] contain much valuable information, and were they not
disfigured by a very eccentric system of arrangement they would approach
nearer to a natural classification of the subfamilies, genera, and
subgenera, than any arrangement of the lesser groups which I have yet
seen.
The species of this group are spread over the whole world, tropical
regions having the greatest variety of forms and number of species.
The _Strigidæ_ are cosmopolitan, most of the genera belonging to both
continents. The _Falconidæ_ are also found the world over, but each
continent has subfamilies peculiar to it. The _Cathartidæ_ are peculiar
to America, having analogous representatives in the Old World in the
subfamily _Vulturinæ_ belonging to the _Falconidæ_, The _Gypogeranidæ_
are found only in South Africa, where a single species, _Gypogeranus
serpentarius_ (GMEL.), sole representative of the family, is found.
As regards the comparative number of species of this order in the two
continents, the Old World is considerably ahead of the New World, which
might be expected from its far greater land area. 581 species are given
in Gray’s Hand List,[6] of which certainly not more than 500, probably
not more than 450, are valid species, the others ranking as geographical
races, or are synonymous with others; of this number about 350 nominal
species are accredited to the Old World. America, however, possesses
the greatest variety of forms, and the great bulk of the Old World
Raptorial fauna is made up chiefly by a large array of species of a few
genera which are represented in America by but one or two, or at most
half a dozen, species. The genera _Aquila_, _Spizætus_, _Accipiter_,
_Haliætus_, _Falco_, _Circus_, _Athene_, _Strix_, and _Buteo_, are
striking examples. As regards the number of peculiar forms, America is
considerably ahead.