BULLOCK ORIOLE. Icterus bullocki (Swainson)

Field characters.—Smaller than Robin. Bill moderately slender, sharp pointed. Male: Plumage conspicuously orange, black, and white. Chin and upper surface of body (including wings but not rump), black; rump and whole under surface of body bright orange or yellow; a large patch of white on fore part of wing; tail black centrally, broadly margined with yellow. Female, and young: Dull olive brown above; breast yellow, and belly and abdomen whitish; wings and tail like back. Voice: Song of male: A slightly varying series of syllables, rhythmically accented, like hip'-kip-y-ty-hoy'-hoy, but with a peculiar quality impossible to describe (fide senior author); also a mildly harsh cha-cha-cha-cha, etc., in rapid sequence, and a single clear note, kleek. Female and young give simple harsh blackbird-like notes.

Occurrence.—Common summer visitant to Lower and Upper Sonoran zones on west side of Sierra Nevada. Recorded at Snelling and Lagrange, and thence eastward to Mount Bullion, El Portal, and 6 miles east of Coulterville. Also east of the mountains in vicinity of Williams Butte, at least as a transient. In Yosemite Valley one bird was noted on May 15 and several on June 3 and 4, 1920 (C. W. Michael, MS). Frequents blue oaks in foothills, and roadside or orchard trees in lowlands. Non-flocking.

The Bullock Oriole is perhaps the most brilliantly colored bird in the whole valley and foothill avifauna. The flashes of orange or bright yellow, black and white in mixed pattern, seen momentarily as a male oriole passes in front of a background of arboreal foliage or along a grass covered hillside, quickly catch the eye and fix attention on the bird. Along all the highways leading toward the mountains, and near the roadways through the foothill belt, this species is common and readily observable throughout the summer months. Moreover, when the birds are not actually seen, their mildly harsh notes coming from a planted poplar or other shade tree often give a clue to the location of a pair busy with nesting duties.

The Bullock Oriole does not remain in this latitude through the winter months when insect forage is scant or wanting. The birds arrive in the Yosemite region in numbers some time in early April. On April 27, 1916, males were present and well established at El Portal. During May, 1915, and again in 1919, the species was much in evidence at our camps in the foothills. But as the season advanced the birds became less and less conspicuous. Our latest record is for August 17, 1915, when a single bird was seen from the window of a train while near Pleasant Valley. East of the mountains, the first migrant for the season of 1916 appeared near Williams Butte on May 8.

In striking contrast to the behavior of the blackbirds, to which it is not distantly related, the Bullock Oriole is, at least during its stay in our latitude, a non-flocking species. Each pair nests by itself and each male presides over a certain rather definite tract of country.

The song of the male Bullock Oriole, as intimated in the small-type paragraph above, is not readily transcribable. The result of an effort to render the song in syllables is included in the following notebook entry by the junior author written on April 27, 1916, at El Portal:

Seated under some blue oaks I am listening to several Bullock Orioles. Four males are spaced about 50 to 100 feet apart in four large oak trees, and each at intervals utters his song. The song goes about as follows: chuck'-ata-chuck, chuck'-ata-chuck, ta-wee'-tah. Intervals between songs are filled with a variety of other notes. A scolding chuck'-ata is often uttered continuously for several seconds. Sometimes this is reduced to chu, chu, chu. Also there is a single explosive note, kleek. This last corresponds to the 'chuck' of the Western Meadowlark. The female scolds in a minor key.

Near Blacks Creek, west of Coulterville, a nearly completed nest of the Bullock Oriole was found on May 10, 1919. The nest was ensconced in the crown of a blue oak which stood beside the main traveled road. The female was doing all the work of building, but her mate stayed within 200 feet of the nest, flying to and from the site at frequent intervals. There were several clumps of mistletoe in this and adjacent trees, but the nest was not hidden in one of these as is often the case with this oriole. To a passer-by the nest might, indeed, at first glance, as seen against the sky amid the oak foliage, have been mistaken for a small clump of the mistletoe. The female was seen to approach the site with a straw in her bill and then to proceed to incorporate it into the structure. She carried the straw inside and there worked it among the grasses already in place. Then she emerged and worked on the outside for a time. The whole structure shook visibly as a result of her energetic efforts. On another occasion when bringing material the female caught sight of the observer. She stopped short and scolded several times, still retaining the straw in her bill. Near Snelling on May 27, 1915, a nest of the Bullock Oriole was seen in a blue oak.

Late in May, 1915, Bullock Orioles at Snelling and Lagrange were busily foraging for insects for their nestlings on the grass covered ravine bottoms and hillsides. A male bird taken on May 26, 1915, at Mount Bullion had some hard parts of grasshoppers in its gizzard.