MONTAGU’S HARRIER. 113 
the natural size of the breast-bone of a young male Pere- 
grine 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 sub- 
stance of the forked bone,* commonly called the merry- 
thought, which is circular, broad, and strong, affording a 
permanent support to the shoulders. . 
By an extended examination of the different species of 
Buzzards and Harriers, it will be found that the characters ° 
described as necessary to produce rapid flight decline gra- 
dually. The sternum decreases in size, the keel loses part 
of its depth, the coracoid bones and furcula become more 
slight ; while the form of the cranium, the loose ruffled fea- 
thers of the neck, as well as the softer and more downy 
texture of the plumage generally, indicate an approach to 
the family next in succession. 
A representation of the sternum of an Owl will be in- 
serted as a vignette to one of the species, to afford a com- 
parative view of the size and structure of the same part in 
~ the diurnal and nocturnal Birds of Prey. 
* Which, when the two sides are united, represents both clavicles. 
