HINTS FOR STUDYING ORNITHOLOGY. 361 
varied. You may perhaps be at a loss to comprehend 
how a swallow, a humming-bird, and a crow, can belong 
to the same order. But look to the characters of the 
order. All birds having their hind toe or toes placed 
upon a level with the ground, are perchers, provided, of 
course, that the claws are not retractile ; for this latter 
circumstance distinguishes the birds of prey. You have, 
therefore, only to see if the foot of a swallow, humming- 
bird, and crow, are so formed: this is your first point 
to ascertain. Other distinctions follow in their proper 
order. Having, therefore, ascertained this primary cha- 
racter, you next look to the bill, the foot, and the claws. 
If the bird before you has the upper mandible distinctly . 
notched, the legs of moderate length, and the toes three 
before and one behind, you may conclude at once that 
it belongs to the tribe of Dentirostres. If, on the con- 
trary, you see that the bill is very slightly, if at all, 
notched near the end, but that the feet are still mode- 
rately long, as in the crow or sparrow, you have the 
general characters of the Conirostres. All other birds 
(and they amount to many hundreds) which do not pos- 
sess these characters, whatever their general appearance 
may be, you may safely throw out of these two prin- 
cipal and typical tribes. You will find that their legs 
are much shorter; that their toes are either united at 
their base, or placed two and two; and that their bill 
is without a notch: they, consequently, belong to the 
large aberrant circle of the Curtipedes, or short-footed 
birds. 
(446.) Here, however, you will begin to see that 
nature’s groups cannot be rigorously defined: and 
this fact will become more and more apparent, in pro- 
portion as you proceed into details. It is one of the 
chief, or typical, distinctions of the Dentirostres to have 
the bill distinctly notched ; but this character disappears 
in some of the titmice (Parus), and is not perceptible — 
in all the mock-birds (Orpheus). The long-legged 
thrushes (Crateropodine) have the bill entire. All these 
groups, nevertheless, have the feet so long, and so per- 
