168 TYRANNIDE, FLYCATCHERS. 
Subfamily TYRANNINA, True Tyrants, 
presenting the following characters :—Wings of 10 primaries, the 1st never spurious 
nor yery short, one or more frequently emarginate or attenuate on the inner web 
a near the end. Tail of 12 rectrices, usually nearly even, 
sometimes deeply forficate. Feet small, weak, exclu- 
sively fitted for perching ; the tarsus little if any longer 
than the middle toe and claw, the anterior toes, 
especially the outer, extensively coherent at base. 
Bill very broad and more or less depressed at the base, 
and tapering to a fine point, thus presenting a more or 
less perfectly triangular outline when viewed from 
above; the tip abruptly deflected and usually plainly 
notched just behind the bend; the culmen smooth and 
rounded transversely, straight or nearly so lengthwise, 
except towards the end; the commissure straight (or 
slightly curved) except at the end; the gonys long, flat, 
not keeled. Nostrils small, circular, strictly basal, 
overhung but not concealed by bristles. Mouth capa- 
cious, its roof somewhat excavated, the rictus ample 
and deeply cleft, the commissural point almost beneath 
the anterior border of the eye. Rictus beset with a 
number of long stiff bristles, sometimes reaching nearly 
to the end of the bill, but generally shorter, and flaring 
outward on each side; there are other bristles or 
bristle-tipped feathers about the base of the bill. The 
bill is very light, gives a resonant sound, in dried 
FiG.110. Emargination of primaries Specimens, when tapped, and on being broken open, 
pin hes the upper mandible will be found extensively hollow. 
These several peculiarities of the bill are the more obvious and important features 
of the group; and will prevent our small olivaceous flycatchers from being con- 
founded with insectivorous Oscines, as the warblers and vireos. 
The structure of the bill is admirably adapted for the capture of winged insects ; 
the broad and deeply fissured mandibles form a capacious mouth, while the long 
bristles are of service in entangling the creatures in the trap and restraining their 
struggles to escape. The shape of the wings and tail confers the power of rapid 
and varied aérial evolutions necessary for the successful pursuit of active flying 
insects. A little practice in field ornithology will enable one to recognize the 
flycatchers from their habit of perching in wait for their prey upon some prominent 
outpost, in a peculiar attitude, with the wings and tail drooped and vibrating in 
readiness for instant action; and of dashing into the air, seizing the passing insect 
with a quick movement and a click of the bill, and then returning to their stand. 
Although some Oscines have somewhat the same habits, these pursue insects from 
place to place, instead of perching in wait at a particular spot, and their forays are 
not made with such admirable élan. Dependent entirely upon insect food, the 
species are necessarily migratory in our latitudes ; they appear with great regularity 
in spring, and depart on the first approach of cold weather in the fall. They are 
distributed over temperate North America; many of them are common birds of the 
Eastern States. The voice, susceptible of little modulation, is usually harsh and 
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