Mr. Xantus found this species, when he first arrived at San Lucas, on the 4th of April, with young birds already fully fledged, although others were still breeding and continued to breed until the middle of July. Two fifths of all the eggs he collected that season, he writes, were of this species. This may, however, have been in part owing to the conspicuous prominence of their nests, as well as to their abundance. Xantus found the nest in various positions. In one instance it was suspended from a leafless branch not three feet from the ground, with its entrance nearly to the ground. In another instance it was on an acacia twenty feet from the ground. For the most part they are hung from low acacia-trees, on the extreme outer branches. In all cases the entrance to the nest was from the lower end, or towards the ground. Dr. J. G. Cooper, in his History of the Birds of California, speaks of finding a large number of this beautiful little bird during the whole winter frequenting the thickets of algarobia and other shrubs, and with habits intermediate between those of Titmice and Warblers, corresponding with their intermediate form. Their song resembles that of the Chickadee, and they also uttered a loud cry, as they sat on high twigs, with a triple lisping note resembling _tzee-tee-tee_. Dr. Cooper found a pair building on the 10th of March. They first formed a wall, nearly spherical in outline, of the thorny twigs of the algarobia, in which tree the nest was usually built. They then lined it with softer twigs, leaves, the down of plants, and feathers. They covered the outside with thorns, until it became a mass as large as a man’s head, or nine inches by five and a half on the outside. The cavity is four and a half inches by two, with an opening on one side just large enough for the bird to enter. On the 27th of March, Dr. Cooper found the first nest containing eggs. These were in all instances four in number, pale blue, with numerous small brown spots, chiefly near the larger end, though some had very few spots and were paler. Their size he gives as .60 by .44 of an inch. In one nest, which he closely observed, the eggs were hatched after about ten days’ incubation, and in two weeks more the young were ready to leave their nest. SUBFAMILY SITTINÆ. The characters of the _Sittinæ_ are expressed with sufficient detail on page 86. The section is represented in America by a single genus, confined mainly to the northern portion. GENUS SITTA, LINNÆUS. _Sitta_, LINNÆUS, Syst. Nat. 1735. (Agassiz.) [Line drawing: _Sitta carolinensis._ 1761 ♀]