90 
NATURAL HISTORY. [EAST. ZOOL. 
slit covered with a valve behind* and the Eagles ( Aguila ) 
and Sea Eagles ( Haliaetus ) have oblong exposed nostrils 
placed perpendicularly across the front of the cere. Among 
the Hawks, the most remarkable bird is the Secretary, 
found at the Cape of Good Hope, called also the Serpent 
Eater, from its preying on those reptiles; the French 
have attempted to naturalize this bird in Martinique, in 
order to destroy the lance-headed serpent, which abounds 
in that island. The Hen Harrier ( Circus ) has some resem¬ 
blance to the Owls. All these birds vary greatly in the 
colour of their plumage before they arrive at the adult 
state. 
The Nocturnal Birds of Prey, or Owls ( Strigidce ), have 
a large head, and their eyes placed in front, and more or less 
surrounded with a circle of radiating feathers. Their 
plumage is very soft, their ears large, and placed just at 
the back of the disk of feathers which surrounds their 
eyes, and this developement of the organs of hearing pro¬ 
bably compensates for the imperfection of their sight, at 
least in full daylight. The Owls have been divided into 
many genera, as the Eagle Owls (Bubo), Short-horned 
Owls ( Otas ), the Earless Owls ( Stria :, Syrnium, and 
Noctaa). The species of the last genus fly more by day 
than the rest of the Owls, and the disk of feathers round 
their eyes is not so distinctly marked as in the other genera. 
The Perching Birds (Passeres Case 36—83) are ge¬ 
nerally smaller than the Raptores, their bills are weaker, 
and their claws slender and acute ; like them, they have 
the hind toes articulated on the same plane with the front 
ones, which enables them to grasp their perch with ease and 
security. They are separated into five divisions, accord¬ 
ing to the form of the feet and bill, each division contain¬ 
ing several families and genera. 
The Passeres of Linnaeus, which contain the greater 
part of these birds, have three toes in front and one behind. 
The two outer toes are generally united together at their base. 
The Fissirostral Birds, or those which feed chiefly on 
the wing, have generally very short weak feet, and large 
gaping mouths; they live principally on insects, though a 
few of the larger kinds catch fish. 
The family of Goat-suckers ( Caprimulgidce ) are noc- 
