338 
COMPARATIVE ZOOLOGY. 
Fig. 324 .— White-throated Sparrow (Zonotrichia 
albicollis). United States. 
merous and varied in the whole class. It comprehends all 
those tribes which live habitually among trees, excepting 
the Rapacious and 
Climbing Birds, and 
whose toes — three 
in front, and one be¬ 
hind—are eminently 
fitted for perching 
only. The legs are 
slender, and seldom 
used for locomo¬ 
tion. 
They are divisible 
into two sections : 
a. Clamatores , with 
nothing in common 
but a harsh voice. In 
most, the tarsus is 
enveloped in a row 
of plates, which meet 
behind in a groove, 
and the bill broad, 
and bent down ab¬ 
ruptly at the tip. 
The typical repre¬ 
sentatives are the 
Tyrant Fly-catchers. 
b. Oscines, or Song¬ 
sters, all of whom 
have a vocal appara¬ 
tus, though all do 
not sing. The an¬ 
terior face of the 
tarsus is one continuous plate, or divided transversely 
into large scales; and the plates on the sides meet be- 
Fio. 325.—Redstart (Setophaga rwticilla). Uuited 
States. 
Fig. 326.— White-eyed Vireo (Vireo Noveboracensis). 
United States. 
