WESTERN WINTER WREN. Nannus hiemalis pacificus (Baird)

Field characters.—Smallest of the wrens; body size less than half that of Junco; tail but little more than an inch in length. Coloration dark reddish brown, below as well as above; an indistinct light line over eye. Tail held always up at steep angle with back. Movements of bird quick; squats every now and then. Voice: A rather extended and varied song of rapid delivery and high pitch; call note, tschep, often given twice in quick succession.

Occurrence.—Sparse summer visitant at middle altitudes on west slope of Sierra Nevada; observed in Yosemite Valley and at Merced Grove Big Trees. Winter visitant in fair numbers to Yosemite Valley, to El Portal, and to Smith Creek east of Coulterville. Lives amid root tangles and brush heaps near streams. Solitary.

The smallest and most reclusive of the wrens in the Yosemite region is the Western Winter Wren. It lives at the middle altitudes, amid freshet-bared tangles of rootlets and accumulations of drift materials along shaded stream courses. The bird is of small size (scarcely so large as a kinglet), and wears a livery of rich dark brown which harmonizes well with its shadowy surroundings. These features, together with its retiring disposition, make of it a species to be seen only when particularly sought for and then only under favoring circumstances.

There are Western Winter Wrens in the Yosemite region at practically all times of year, but a larger number of individuals is present in winter, and the species is then to be found in several places not inhabited in summer. Whether the summer population moves out with the coming of fall is not known, but it is obvious that a considerable quota arrives from the north in October and remains here for at least a part of the winter has nested near Bower Cave. With so many seemingly favorable localities in the region it is surprising that other instances of summer occurrence have not been noted.

The winter range includes such stations as Yosemite Valley, El Portal, and Dudley, on Smith Creek, six miles east of Coulterville. An individual bird collected at Ten Lakes on October 9, 1915, is the basis of our earliest record for the species outside the local breeding area; this bird may have been only a transient, for this locality is in the Hudsonian Zone. It seems unlikely that the species could winter successfully in the territory above the Transition Zone.

Individuals were observed along the Wawona road near Chinquapin, November 26, 1914, and on the South Fork of the Tuolumne River at the Hog Ranch road, October 15, 1915. These birds also may have moved to lower stations with the coming of the heavy snows later in the winter.

The number of individuals present in winter, while greatly exceeding the summer population, is not large as compared with the numbers of other species of birds. On Sweetwater Creek, late in October, 1915, 3 Western Winter Wrens were living within a stretch of about 400 feet of cañon bottom; but this was an exceptional concentration. Elsewhere there is perhaps not more than one every two or three hundred yards.

Wrens as a group are possessed of mercurial temperaments and the Winter Wren is among the most 'nervous' of its kind. The bird seems never to be quiet, but is constantly twitching about from side to side, frequently bobbing down and up, always with the short tail cocked at a decided angle with the back. The bird seems to skip along and uses both the short wings and long legs in all its ordinary movements. It seems equally at ease on a nearly vertical twig and on a horizontal root or branchlet. A great deal of its foraging is done in under the overhanging banks. Quite often the bird is lost to the observer's sight amid the crannies and shadows about the base of some large stream-side tree, and comes into view only now and then.

The song is difficult to describe. It consists of a number of notes run together quickly with no rests within the song itself. Some one has compared the Winter Wren's song to the noise made by a squeaking gate hinge, but the comparison is not a specially happy one. The song is heard sometimes during the winter months, and commonly, as is indicated by Mr. Torrey's record, at nesting time. The call note of the species, a short tschep, is heard more frequently, and throughout the year; sometimes it is given twice in quick succession. An observer can make a good imitation of the note by drawing the tongue backward from the clenched teeth and closing the lips at the same instant. We have commonly used this sound in attracting a bird for a close view.

One evening just at sunset, in October, while our party was camped near Sweetwater Creek, a winter wren was watched as it came down to bathe. The bird fluttered down, half flying, half hopping, to a small pool completely screened from above. It would stay a few seconds, splashing in the water, and then move to a perch a few feet above the pool, soon to return for another brief dip. Five or six such short visits were made and then the bird returned to the perch where it stayed for a while, fluffing out all its feathers, and using its bill to press out the water. Two or three minutes sufficed to complete its toilet and then the wren made off down the creek to a brush pile.

The only Yosemite nest of the winter wren of which we have record was seen on May 28, 1911, near Happy Isles. It was a rather bulky affair, made of soft materials and situated in a tangle of pendant rootlets beneath the butt of an old prostrate log. The place was shaded by incense cedars, Douglas spruces, and black oaks. Beneath the log flowed a little stream about 3 feet wide and the nest entrance was only 13 inches above the water. Twenty feet away was the torrent of the Merced River. There were 4 (possibly more) large young in the nest, but only one of the parent birds was in evidence. The presence of two trout in the stream below, and the fear of these shown by the adult wren, suggested that the other member of the pair might have fallen victim to one of the fishes. The parent was busily engaged in feeding large green worms, millers, crane-flies, and other insects to the young. A beam of light reflected into the nest from a mirror did not seem to frighten the wrens and so it was possible to observe closely the process of feeding. The old bird made visits at intervals of 4, 9, 2, 2, 7, 8, and 3 minutes, respectively; twice, at the second and the last of these timed visits, the bird carried away excrement. The young void the excrement (which is enclosed in a gelatinous sac) immediately after being fed; it is dropped by them on the rim of the nest where it lies as a conspicuous spherical white object, the size of a large bean. The old bird seizes this in her bill and in one instance carried it away fully 50 feet before depositing it in a wild currant bush. One sac fell into the small stream and as it floated slowly along the surface the bird snatched nervously at it again and again. Finally it was recovered, whereupon the bird flew off and disposed of it in the usual manner, in a place where it would give no clue to the location of the nest.