SP. CHAR. Above cinereous; head, all round, yellow; lesser wing-coverts chestnut; beneath brownish-white. Length, 4.50 inches; wing, 2.16; tail, 2.35. HAB. Valleys of the Rio Grande and Colorado; Cape St. Lucas. [Line drawing: _Auriparus flaviceps._ 6764] HABITS. This new and interesting little species was first added to our fauna by Mr. Lawrence in 1851, only a year after its first description as a bird of Mexico. Notwithstanding the abundance in which it has been in certain localities, less has been developed in regard to its habits and specific characteristics than we seem to have had a right to anticipate. It was found in Western Texas, in Mexico, in the lower valleys of New Mexico and Arizona, and is very abundant at Cape St. Lucas. Of the eighteen species of birds found by Mr. John Xantus breeding in the last-named locality, this one was regarded as the most abundant. In a letter from that gentleman, written in August, 1859, he mentioned that he had collected over one hundred eggs of this species, during that season, in the immediate vicinity of Cape St. Lucas. [Illustration: _Auriparus flaviceps._] Dr. Heermann, in his report on the birds observed in Lieutenant Williamson’s explorations, states that he first discovered this species in Southern California, at the terminus of the Mohave River. Owing to their extreme wildness, he was not able to obtain any specimens. In searching for their food, he states that they often remained suspended with their backs downward, after the manner of the Titmice. He found their nests quite abundant, though from the lateness of the season few of the birds were remaining, in the neighborhood of Fort Yuma. Dr. Heermann describes their nests as spherical, formed of twigs, and having the entrance on one side. The interior was lined with down and feathers, and contained usually from four to six eggs. These he describes as having, when fresh, a ground-color of pale blue, dashed all over with small black spots. Dr. Kennerly, in his Report on the Birds of the Mexican Boundary Survey, states that he met with this species in the vicinity of the Rio Grande. They were very wild, flew rapidly, and to quite a distance before they alighted. They seemed to frequent the low mezquite-bushes on the hillsides.