U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 
EMPIDONAX FLAVIVENTRIS, B a i r d . 
Yellow-bellied Flycatcher. 
Tyranmda flaviventris, Wji. M. and S. F. Baird, Pr. Ac. Nat. Sc. Phila. I, July, 1843, 283— In. Am. Journ. Science, 
April, 1844.— Audubon, Birds Amcr. VII, 1844, 341 ; pi 490. 
Tyrannula pusilht, (Swainson) Reinhardt, Vidensk. Meddel. for 1853 1854, 82.— GLOGER,;Cab. Jour. 1854, 426. 
Empidonax hypoxanthus, Baird, (Provisional name for eastern specimens.) 
Empidonax difficilis, Baird, (Provisional name for western.) 
Sp. Ch.— Second, third, and fourth quills nearly equal ; first intermediate between fifth and sixth. Tail nearly even, slightly 
rounded. Tarsi long. Above bright olive green; (very similar to the back of Vireo noveboracensis ;) crown rather darker. 
A broad yellow ring round the eye The sides of the head, neck, breast and body, and a band across the breast like the back, 
but lighter ; the rest of the lower parts bright sulphur yellow ; no white or ashy anywhere on the body. Quills dark brown ; 
two bands on the wing formed by the tips of the primary and secondary coverts, the outer edge of the first primary and of the 
secondaries and tertials pale yellow, or greenish yellow. The tail feathers brown, with the exterior edges like the back. The 
bill dark brown above, yellow beneath. The feet black. In the autumn the colors are purer, the yellow is deeper, and the 
markings on the wings of an ochry tint. Length, 5.15 inches ; wing, 2.83 ; tail, 2.45. 
Ilab.— Eastern United States generally. Probably replaced on the Pacific by a closely allied species. 
This species is thick set in form ; the wings long, reaching as far as the middle of the tail, 
or to the end of the upper coverts. The relative proportions of the second, third, and fourth 
quills vary somewhat ; the third is, however, mostly a little the longest. The first is generally 
a very little longer than the sixth ; considerably shorter than the fifth ; it is about .40 shorter 
than the longest, which exceeds the secondaries by about .65 of an inch. The tail feathers are 
rather narrow, and rather acute ; the lateral ones a little shortest. The bill is rather broad. 
This species is about the size of E. minimus, though rather stouter. The bill is broader ; 
the colors are different, minimus not having the bright olive green of the back and yellow of 
the under parts, even on the throat, which instead is whitish. In respect to color, flaviventris 
differs materially from all our North American species. 
This species differs from some North American flycatchers in not having the uppermost tarsal 
scutellae to envelope the outside of the bone, but reach only half way round, where the edge of 
another series is seen opposite the first. The lower scales, however, follow the usual rule. 
There is no naked space on the inner face of the tarsus. 
Although the specimens from the west coast are not sufficiently perfect to allow of a full 
criticism, I am inclined to think that they are really distinct, and that they will not constitute 
almost the single exception to the fact that no flycatcher is common to both east and west 
coasts. The colors are lighter, and duller ; the olive more yellowish, and the bands and 
edges of the wings narrower and less distinct. The forehead has a peculiar hoary appearance. 
The first quill is intermediate between the sixth and seventh, and half an inch less than the 
longest ; the second considerably shorter than the fourth. In flaviventris the first is rather 
longer than the sixth ; the second and fourth equal. In view of all these circumstances, there- 
fore, it may be well to give it provisionally a new name, and none would be more appropriate 
than that of Empidonax difficilis. 
The Muscicaprt flaviventris of Vieillot (Ois. Am. Sept. I, 1807, 70) is clearly distinct in the 
larger size, rufous tinge above, absence of yellowish on the throat and breast, &c. What the 
species really is is not well ascertained, nor whether it actually belongs to this group. It is 
spoken of as inhabiting St. Domingo. Should it prove to be of the same genus the present 
species may be called hypoxanthus in allusion to the yellow of the under parts. 
