DOTTED CAÑON WREN. Catherpes mexicanus punctulatus Ridgway

Field characters.—Size more than half that of Junco; tail shorter than body; bill long (3/4 inch) and slender. Coloration rich reddish brown; throat and chest clear white. (See pl. 53c). Executes squatting movement every few seconds, by which white of throat area is emphasized. Voice: Song a series of ten or so loud clear whistled notes, the pitch descending and the timing faster toward end of series; call note a short, hoarse bzert.

Occurrence.—Resident in fair numbers from Lower Sonoran Zone up through Transition on west side of Sierra Nevada.³⁷ Recorded from near Snelling and Lagrange eastward through Yosemite Valley, and, in late summer, to Merced Lake. Chiefly on and about rock walls of the larger cañons. Solitary.

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³⁷The Cañon Wren has been reported from the vicinity of Mono Lake by Dr. W. K. Fisher (1902, pp. 7, 11), who saw one or more of the birds there in September, 1901. None was seen by either of our field parties which visited that region in the fall of 1915 and the spring and summer of 1916. In the absence of specimens the subspecies represented on the east side remains in doubt.

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One usually gets his first knowledge of the Dotted Cañon Wren through hearing its clear, musical song from high up on the wall of some cañon. In Yosemite Valley the notes of the song are often to be heard coming from the surrounding cliffs, dominating all other sounds because of their remarkable carrying power. Only persistent observation will bring acquaintance with the bird itself. The emphatic bobbing movement of the body, the rich brown coloration, and the strong contrast between the pure white throat and chest (pl. 53c) and the dark body render this wren, when once within view, easy to recognize both as distinct from the members of its own tribe and from other song birds in general.

The species is common in the lower cañon of the Merced River, from Pleasant Valley to El Portal. Some individuals also live about the earth bluffs and rock outcrops near Merced Falls, and others dwell on the glacier-scoured walls of the Yosemite Valley. A few venture even into the lower Tenaya Cañon and the Little Yosemite. Finally, several birds were noted by us in the vicinity of Merced Lake, well within the Canadian Zone, August 23 to September 1, 1915. Whether these latter had nested at so great an altitude, and whether they would have wintered there, were points not determined. It is possible that here was a case of local wandering after the close of the nesting period.

The preferred habitat of the Cañon Wren consists of broken rock surfaces, such as abound in parts of the region; yet fallen logs, old buildings, and even inhabited houses come within the forage range of certain individuals. No satisfactory estimate of numbers can be given, because of the irregularity in the occurrence of suitable surroundings. At Pleasant Valley 6 individuals in different directions could be heard during a certain 10-minute walk; in Yosemite Valley 2 singing males were sometimes within hearing at one time; elsewhere the birds are as a rule much more widely scattered than indicated by the observations just cited.

At El Portal a Cañon Wren frequented the cabin in which our indoor work at that station was done. The bird would come in at various hours of the day and proceed to zigzag about the floor, pursuing flies and spiders. It would poke bill and head into crevices and at times even crawl all through the space between the inner and outer walls of the drafty building. At Pleasant Valley, in May, 1915, the station house was similarly tenanted, and the agent there complained mildly that the birds, hopping across the desk and tables, interfered with his work.

Crevices and crannies in rock walls and caverns and openings between talus rocks are explored to their limits by the birds. Like the Rock Wren, the Cañon Wren has acquired a special flatness of body structure, which is an obvious adaptation to allow it passage through horizontal crevices. This is a quite different adaptation from that in a rail, whose narrow compressed body, thin from side to side, allows progress through the vertical interstices among standing reeds.

Were the Cañon Wren less active, its disruptive scheme of coloration would be exceedingly effective in rendering it inconspicuous; but its almost incessant bobbing movements make the bird easy to see against almost any tone of background. Even in the dark recesses of a deep cavern the white throat patch is, because of this motion, surprisingly conspicuous.

When foraging, the Cañon Wren travels apparently with equal facility on rock, earth bank, and wall of building; it moves by short hops of two or three inches, and usually changes direction, or zigzags, with every few of these 'hitches.' The bird's legs (tarsi) are short and are held at an acute angle with the surface on which it is traveling, so that the body is close to the substratum. At intervals of two to twelve seconds the hinder parts are slowly raised and then instantaneously depressed. So quickly and violently is this done that the whole body is drawn into the movement. This is the characteristic bobbing referred to above.

The song of the Cañon Wren is one of its most notable features. Many wrens have throaty or bubbling songs; but only in its call note does this species utter anything like the notes of its relatives. The song is a series of clear undulating musical whistles, starting high and, with individual notes well separated but with lessening intervals, descending gradually in pitch to an abrupt low ending. Some songs studied in detail included ten to fifteen notes. The call, a rather hoarse, low-pitched bzert, is uttered now and then when the birds are foraging. The song is to be heard at any time of day, from dawn until dark, throughout the nesting season; and it does not entirely cease when the broods are reared, for we have heard it during late July and August. There is a revival or continuance of song in winter. For instance, on December 19, 1914, one of these birds on the cliff near Yosemite Falls gave three full songs at late dusk (5:05 P.M.) when the air was freezing cold and icicles two feet in length were hanging from the rocks.

The nest of the Cañon Wren is commonly placed on ledges in rock caverns, but in the foothills of the Yosemite country situations in weathered buildings are sometimes used. Near Lagrange, on May 8 and 9, 1919, a pair of these birds was engaged in carrying food to a brood of young in a downward slanting crevice at the base of an earth bank in a ravine. The nest was not in sight but was evidently located somewhere below the level of the ground outside.

At Pleasant Valley a nest under construction on May 17, 1915, was situated inside a storehouse, on a beam beneath the gable and about fifteen feet from the floor. On May 25 there were 3 fresh eggs which by May 30 had been increased to 5, 3 of which at that time showed the beginnings of incubation. The base of the nest was composed of a pile of irregularly placed twigs, upon which had been heaped scraps of rotted wood and other debris, while the inner wall was thickly felted with old cotton and then lined separately with mammal hair. Another nest, in which a brood had been reared, was in the station house at the same place. Two fully fledged young birds were seen there on May 29, 1915. A brood of bob-tailed young was seen on the north wall of Yosemite Valley near Rocky Point on July 27, 1915.

The short irregular movements of the Cañon Wren when hopping about the rocks are made largely for the purpose of spying out food. The bird darts here and there, examining crannies and crevices and making selections from the insect population to be found in such places. The wren seen in the cabin at El Portal gathered large numbers of the flies and spiders which had been benumbed by the chilling cold of an early December morning; it was an easy matter then for the wren to accumulate a meal in short order; but later in the day, as the insects became warmed up, the bird did not fare so successfully. The Cañon Wrens which inhabit the walls of the Yosemite Valley seem to find adequate forage in the crevices of the granite and amid the jagged rocks of the talus slopes, where they go into all sorts of dark corners in their searches for food. The mantle of snow in midwinter is no hindrance to their activity. The birds then work far back in the protected caverns, often altogether beyond the reach of the human eye. Only the echoing bzert indicates their presence there.