WESTERN RED-TAILED HAWK. Buteo borealis calurus Cassin

Field characters.—Size large, equaling that of Turkey Buzzard; tail short, usually held broadly fan-shaped in flight (pl. 44c). Upper surface of body (except tail in adults), dark chocolate brown; under surface of body varying from dark brown to almost white, in different individuals; tail bright reddish brown in adults. Most often seen sailing about in circles overhead; sails and glides much, with few wing strokes. Voice: A shrill, long-drawn-out, whistled squee-oo, uttered once, or several times in slow succession.

Occurrence.—Resident in some numbers throughout the entire Yosemite region. Noted as high as summit of Parson's Peak, over 12,000 feet altitude.

The Western Red-tailed Hawk is a regular resident of the whole Yosemite region, ranging from the cottonwood groves along the Merced River at Snelling up to the Sierran crest, and also farther to the eastward, about Mono Lake. It is not so abundant here, however, as in many other parts of California, for even an experienced observer rarely sees, in a day's walk anywhere in the Yosemite section, more than one or perhaps a pair of the birds.

Sixteen species of diurnal birds of prey inhabit the Yosemite region, but only four of these, the Osprey, Goshawk, Ferruginous Rough-leg, and the Turkey Buzzard, equal the Red-tail in size, and but one, the Golden Eagle, exceeds it. (See pl. 44). The Eagle has a golden-tinted head and neck; the Osprey's head and under surface are chiefly pure white; the Goshawk is gray-appearing in plumage and it has a long tail; the Ferruginous Rough-leg is conspicuously white beneath and has much white showing at base of tail; and the Turkey Buzzard has a bare red head, black plumage, and a gray area on the under surface of each wing near the tip. Among the hawks of somewhat smaller size, the Swainson has a conspicuously light chin and throat, the Red-bellied, plainly black-and-white barred wings and tail, and the Marsh Hawk, a white rump. None of these other birds has a reddish brown tail in any plumage.

There is much variation in the color of the under surface of the body in different individuals of this species. Some have the under surface as well as the back almost black, while others are nearly white below, with few or no streaks or other markings. Such peculiarities are individual, and cannot be correlated with sex or season. The tail in immature birds is dull, much like the back in color; but all adults, regardless of 'color phase,' have bright reddish brown tails.

The Red-tail is essentially a soaring hawk. The Marsh and Sparrow hawks when hunting beat along over grassland or poise hovering in the air, and the bullet hawks (Cooper and Sharp-shinned hawks, and Goshawks) usually dart after their prey in or through trees or brush; but the Red-tail proceeds in seemingly more leisurely fashion, and in the open. It sails about with wings and tail widely spread (pl. 44c) and watches from on high for its prey. Occasionally it may perch on a fence post and watch the field near by for ground squirrels or gophers, upon which it pounces with alacrity remarkable in a bird with so heavy a body.

At times Red-tails are to be seen perched in conspicuous places on branches of dead trees where they can see for considerable distances. If a person comes suddenly under a bird so resting, it gets up quickly and with heavy sweeps of its large wings rapidly gains momentum and begins to glide and sail in a spiral course; it is soon able, without seeming to change much the relative positions of either wings or tail, to mount high into the air.

The Red-tail is to be considered a beneficial species, as regards the interests of mankind; for it lives to a large extent on ground squirrels and gophers. Despite this fact, many people, having in mind the name 'chicken-hawk' which is erroneously applied to the bird, wage relentless warfare on it when their militant efforts ought by rights to be directed exclusively against the bullet hawks. Of course an occasional Red-tail, just like an occasional human being, departs from the normal habits of its race and becomes harmful to man's general interests, and may quite properly be given summary treatment.

In mid-December near Lagrange five old nests of the Red-tail Hawk were found in an earth bluff about 25 feet high. The nests were in open situations about 8 feet below the top of the bluff and probably represented the choices of sites by one pair of hawks through a number of successive years. Under one of them were found the remains of ground squirrels and much 'white-wash' (droppings), which indicated that a brood of young had been reared there earlier in the year. At Mono Meadow on June 16, 1915, a Red-tail was seen frequenting a neighboring ridge; it kept up its cries so continuously as to suggest the presence of a nest in the vicinity.

The famous "eagle's nest" in Bower Cave is nothing more than a nest of the Red-tailed Hawk. It is situated in a niche of the rock wall below the rim of the cave where, because it is so thoroughly sheltered from the weather, it remains in a fair state of preservation although it has been unused now for many years.