MOUNTAIN BLUEBIRD ENTERING HIS NEST-HOLE. Photographed by W. F. Badè, July 29, 1911, at Tilden Lake; altitude, 9,000 feet. chosen the uppermost of three abandoned woodpecker holes, and, at the time I found them, were quite busy carrying food to their nestlings. While thus employed, I secured several photographs, one of which is reproduced with this article. In my experience the Mountain Bluebirds are a little shyer than other bluebirds. As soon as one approaches their nest, they alight near by, fly nervously from perch to perch, and utter a plaintive call note which resembles that of the Western Bluebird. There is a great scarcity of information regarding the song of the Mountain Bluebird. Members of the Sierra Club may contribute something on this point by their observations. Minot, in the Bulletin of the Nuttall Ornithological Club (Vol. V, page 225), describes its song notes as less plaintive, deeper in tone, and uttered with a richer warble than that of the ordinary bluebird. Other observers describe the bird as markedly silent, or omit all reference to its notes and song. Robert Ridgway, in his report on the Ornithology of the Fortieth Parallel (1877) calls attention, in the case of the Mountain Bluebird, to what he describes as a change of habits due to spreading civilization. He found these bluebirds nesting numerously about buildings at Salt Lake City. Had the site of the city remained in its primitive, unreclaimed state, he says, the birds would undoubtedly have been found there only during their vertical migrations, influenced by changes of climate. As Mr. Joseph Grinnell observed, in a conversation with the writer, this is not strictly to be described as a change of habits. In taking to buildings, bird-houses, or mailboxes* for a choice of nesting sites, they still are essentially exercising the habit of selecting the comforts provided by hollow trees, woodpecker holes, or crevices among rocks. Cliff-swallows, Swifts, and some Wrens have been doing the same thing. It is noteworthy, however, as Mr. Ridgway points out, that the availability Condor, Vol. XIV, No. 3. of desirable nesting sites around human habitations has, in at least one instance, caused the Mountain Bluebird to forsake its alpine breeding-ground for levels at which its does not ordinarily breed. There can be no doubt that in the Sierra Nevada Sialia arctica is a true mountaineer. They are most abundant from an altitude of 9,000 to 11,000 feet. There one may see them, as in the accompanying photographs, conducting their housekeeping in woodpecker holes or hollow trees. There they hover, like great azure butterflies, over the luscious green of alpine meadows. And Ridgway reports that he saw them on the heights, sporting with apparent delight among the snowflakes of oncoming winter storms, when other birds were seeking shelter in cozy copses. Severe climatic changes, however, usually start them on their vertical migration to the lower valleys. On the floor of the Hetch Hetchy Valley and in similar localities of the transition zone, up to the Murray pine meadows, the Western Wood Pewee (Myiochanes richardsonii) was found breeding in considerable numbers. It wears a livery of dark grayish brown above, shading on the under parts into whitish or pale yellowish, washed with dark gray. The Wood Pewee has the alert appearance and many of the actions of a small flycatcher. Its quiet call, a liquid tweer, uttered from its perch on the dry branch of a tree as it watches for insects, lingers long in a Sierran camper's memory of tranquil noon hours in sunny woodlands. The trout angler is apt to find the Wood Pewee's nest while casting along the banks of streams where black cottonwoods (Populus trichocarpa) and white alders (Alnus rhombifolia) stand guard against ranks of yellow pines and incense cedars. In every case I found the nest saddled on the horizontal branch of a tree, at heights varying from eight to twenty feet, and usually above the water. They were, of course, found also in other situations, but most often along the streams. |