OF EASTERN PENNSYLVANIA. >:> 



of the deflection ; culmen smooth and rounded transversely, 

 straight or nearly so longitudinally, excepting towards the ex- 

 tremity ; the commissure straight, or delicately curved except 

 toward the end ; gomys long, flat, and devoid of keel. Nos- 

 trils small, circular, truly basal, and overhung, but not hid- 

 den, by bristles. Mouth large, roof somewhat hollowed ; 

 rictus full and profoundly cleft ; commissural point, just be- 

 low the anterior margin of the eye. The rictus is beset with 

 long, rigid bristles, occasionally, but not always, which extend 

 nearly to the end of the bill, and flare outwardly on each 

 side. About the base of the bill, exist other bristles, or bris- 

 tly-tipped feathers. Dried specimens of the bill when tap- 

 ped, produce a resonant sound, which is probably due to 

 the concavity which the upper mandible reveals when broken 

 open. These obvious and striking features will enable us to 

 clearly distinguish our smaller olivaceous fly-catchers from 

 the insectivorous Oscines^ as the warblers and vireos. with 

 which they are likely to be confounded. 



The structure of the bill is eminently fitted for the sei/ure 

 of winged insects. The wide and profoundly fissured man- 

 dibles, constitute a capacious orifice, while the long rictal 

 bristles serve to entangle the creatures and check their strug- 

 gles to escape. The configuration of the alar and caudal 

 appendages, confers that power of rapid and varied aerial 

 movements, necessary for the successful pursuit of agile fly- 

 ing insects. Their peculiar habit of perching upon some 

 conspicuous outpost, with the wings and tail drooped, and 

 waiting in readiness for immediate action ; their dashing into 

 the air, seizure of the passing insect with an astonishing 

 celerity of movement and a sharp click, and their speedy re- 

 turn to the same position, are so familiar that even at a long- 

 distance, the sharp eye of the practised ornithologist cannot 

 mistake their identity. Although some Oscincs have simi- 

 lar habits, these pursue insects from place to place, but \\ilh 

 less dexterity. The species are necessarily migratory, their 

 vernal coming and autumnal departure, being wholly depen- 

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