Immature males sometimes have the white on the wing tinged with brownish-yellow, as in _A. phœniceus_. The red, however, has the usual brownish-orange shade so much darker and duller than the brilliantly scarlet shoulders of the other species, and the black has that soft bluish lustre peculiar to the species. The relationships generally between the two species are very close, but the bill, as stated, is slenderer and more sulcate in _tricolor_, the tail much more nearly even; the first primary longer, usually nearly equal to or longer than the fourth, instead of the fifth. Two strong features of coloration distinguish the female and immature stages of this species from _gubernator_ and _phœniceus_. They are, first, the soft bluish gloss of the males, both adult and immature; and secondly, the clear white and broad, not brown and narrow, borders to the middle wing-coverts. HABITS. The Red and White shouldered Blackbird was seen by Mr. Ridgway among the _tulé_ in the neighborhood of Sacramento City, where it was very abundant, associating with the _A. phœniceus_ and _gubernator_, and the Yellow-headed Blackbird. The conspicuous white stripe on the wings of this bird renders it easily recognizable from the other species, where they are all seen together. Mr. Ridgway is of the opinion that the notes of the white-shouldered species differ very considerably from those of the two other Blackbirds. Dr. Heermann found this a very abundant bird in California. He states that during the winter of 1852, when hunting in the marshes of Suisan Valley, he had often, on hearing a dull, rushing, roaring noise, found that it was produced by a single flock of this species, numbering so many thousands as to darken the sky for some distance by their masses. In the northern part of California he met with a breeding-place of this species that occupied several acres, covered with alder-bushes and willow, and was in the immediate vicinity of water. The nests, often four or five in the same bush, were composed of mud and straw, and lined with fine grasses. The eggs he describes as dark blue, marked with lines and spots of dark umber and a few light purple dashes. Dr. Heermann, at different times, fell in with several other breeding-places of this species, similarly situated, but they had all been abandoned, from which he inferred that each year different grounds are resorted to by these birds for the purposes of incubation. Dr. Kennerly obtained a specimen of this bird on the Colorado River, in California, December, 1854. Dr. Cooper is of the opinion that it is, nevertheless, a rare species in that valley. The latter found them the most abundant species near San Diego and Los Angeles, and not rare at Santa Barbara. North of the last place they pass more into the interior, and extend up as far as Klamath Lake and Southern Oregon.