Plumages.—Young Sennett’s warblers that I have examined are uniform grayish olive above, inclining to olive-green on the back; the black lores and cheeks are lacking; the median wing coverts are narrowly tipped with whitish, and the greater coverts more broadly so; the chin is pale yellow; the chest and upper breast are shaded with pale gray and centrally tinged yellowish; the abdomen is dull white; and the sides and flanks are shaded with pale olive-grayish. I have not seen enough material to trace subsequent molts and plumages, which doubtless parallel those of the parula warbler.
Food.—We have no definite information about the food of Sennett’s warbler, but Clarence F. Smith has sent me the following note: “The only laboratory report available on the food of the species pertains specifically to a South American subspecies of the pitiayumi group. The stomach contents were reported to consist of remains of hymenopterous insects and two-winged flies (Zotta, 1932).”
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Nothing further seems to have appeared in print regarding the habits of this warbler. It is much like the well-known parula warbler in appearance and behavior, but can be recognized in the field by the conspicuous black lores and cheeks and by the complete absence of any pectoral band.
DISTRIBUTION
Range.—The species ranges from southern Texas to northern Argentina and Uruguay. The race occurring in the United States is found in southern Texas and northeastern Mexico.
Breeding range.—Sennett’s olive-backed warbler breeds north to northeastern Coahuila (Sabinas); and southern Texas (Hidalgo, Harlingen, and Point Isabel). East to southern Texas (Point Isabel and Brownsville); and southeastern Tamaulipas (Altamira and Tampico). South to southern Tamaulipas (Tampico); and southern San Luis Potosí (Valles). West to eastern San Luis Potosí (Valles); and eastern Coahuila (Cerro de la Silla and Sabinas).
Winter range.—While probably not a sedentary form, its winter range very nearly coincides with its breeding range. It has been found in winter from Brownsville, Tex., to northern Hidalgo (Jacala).
Egg dates.—Texas: 6 records, April 28 to May 30; 4 records, May 2 to 12, indicating the height of the season.
Mexico: 2 records, May 27 and July 5.