FALCONIDjE.
the centre of each feather; under surface of tail-feathers
barred with greyish white and brown ; legs, toes, and claws
as in the adult male.
A young male in the plumage of the first year has the
head and neck ferruginous, each feather with a central lanceolate
patch of dark brown ; back and wings umber brown ;
wing-coverts with broad ferruginous margins; primaries
brownish black; secondaries and tertials tipped with rufous ;
upper tail-coverts white, tipped with re d ; upper surface of
the tail-feathers with five bands of dark brown, and four
bands of greyish brown ; ear-coverts uniform umber brown ;
chin, throat, breast, belly, thighs, and under tail-coverts,
uniform reddish brown; under surface of wings the same;
under surface of tail-feathers dull reddish white, with four
or five bands of brownish grey; legs, toes, and claws, as
in older birds.
The adult female of Montagu’s Harrier measures nineteen
inches; the beak black ; the cere dull yellow; the
irides hazel; crown of the head and nape reddish brown,
with darker brown spots; above and below the eye a streak
of dull white ; ear-coverts dark brown ; back and wings dark
umber brown; rump and upper tail-coverts mixed with white
and orange brown; upper surface of the central tail-feathers
uniform dark brown; lateral tail-feathers barred with two
shades of brown; breast, belly, and all the under surface of
the body, light reddish brown, with longitudinal marks of a
darker colour ; legs and toes yellow; claws black. In very
old females of this species the general colour of the plumage
is lighter, and the irides become bright yellow. Young
females have the whole of the under parts from the throat
to the under tail-coverts of a uniform reddish bay, without
any of the darker-coloured streaks observable in adult females.
Having thus described the last of the British Falconida,
Montagu’s harr ier. 105
it may be desirable, before quitting this group, to exhibit a
representation of the breast-bone, or sternum, of one of the
types of the Falcons, in order to show in the form and magnitude
of the principal bone, and the others attached to it,
the power of flight possessed by these birds, of which the
breast-bone affords good comparative indication.
The power of flight is one of the decided characteristics
of the organization of the class of Birds; and the division
of the Falconida includes those birds which appear to possess
this power in the highest degree of perfection. The
conditions necessary to produce this power in its fullest extent
are, large and strong pectoral muscles; great extent of
surface, as well as peculiarity of form, in the wing; and
feathers of firm texture, strong in the shaft, with the filaments
of the plume arranged and connected to resist pressure from
below. The extent of surface, the form and other peculiarities
of the wings, have been already noticed, and the
anatomical part only requires to be briefly described. A
certain degree of specific gravity is necessary to rapid flight,
and this is imparted by large pectoral muscles; the power
of these muscles may be estimated by the depth of the keel,
and the breadth of the sides of the breast-bone or sternum,
as affording extent of surface for the attachment of those
large muscles by the action of which the wings are brought
down.
As an illustration of this form, the figure here inserted as
a vignette is a representation about one-fourth less than the
natural size of the breast-bone of a young male Peregrine
Falcon, which exhibits the depth of the keel, the breadth of
the sides, as well as the strength of the coracoid bones; and
the power of flight peculiar to all the species of Falcons is still
further illustrated by the form and substance of the forked
bone,* commonly called the merrythought, which is circular,
* Which, when the two sides are united, represents both clavicles.