With regard to the nesting habits of this Owl, Captain Charles Bendire says: "While perhaps the majority of these birds resort to hollow trees or old nests of the larger hawks and of the common crow, quite a number nest in the wind-worn holes in sandstone and other cliffs, small caves in clay and chalk bluffs, in some localities on the ground, and, I believe, even occasionally in badger holes under ground. On the grassy plains in the Umatilla Indian Reservation, in northeastern Oregon, I have several times seen Owls of this race sitting on the little mounds in front of badger or coyote burrows, near the mouths of which small bones and pellets of fur were scattered about. While unable to assert positively that they do actually breed occasionally in such holes, the indications point that way, and this would not seem to be due to the absence of suitable timber, as an abundance of trees grow along the banks of the Umatilla river not more than a mile away. When nesting in trees, large cottonwoods, sycamores, willows, pecans, pines, oaks and firs are generally preferred. In regions, however, where heavy timber is scarce, they content themselves with nests in small mesquite and hackberry trees, frequently placed not more than ten feet from the ground." Captain Bendire also states that they have been known to use the nests of the black-billed magpie, either laying their eggs on the inside of these curiously built and enormous structures or on the broken-down roofs. These nests are well adapted to the requirements of the Owl, for they vary from one to three feet in diameter and are constructed in a very substantial manner. The foundations consist of twigs held together with mud, and upon this, built of smaller twigs, is the nest, which is plastered with mud and lined with grass and small roots. The whole structure is surrounded by dead twigs, which form an arch over the top of the nest. This is a palace which the Owl would never take the trouble to construct, but is willing to use. It is said that the Western Horned Owl will lay two or more sets of eggs at short intervals if the nest and eggs are disturbed, and an instance has been recorded where three sets of eggs have been taken from the nest of a single pair at intervals of about four weeks. The number of eggs laid is usually two or three, and infrequently four are found and sets of five and six have been reported. The eggs are white, showing, as a rule, but little gloss and are roughish. In form they are rounded oval, about two and one-half inches long, and nearly two inches in diameter. The period of incubation lasts about four weeks, and it is said that only the female sets on the eggs, the male furnishing her with food. Like the Great Horned Owl this variety is quite solitary in its habits, except during the breeding season, and is almost as destructive as that bird which is considered the most destructive of all the Owls.