334 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



perhaps not so common in the lowlands as the barn owl, the Pacific 

 horned owl is often seen and reported, both because of its great size 

 and because of the interest that its presence always creates. It lives 

 along the wooded river bottoms of the lowlands, in the wooded foot- 

 hill ravines, and in the forests of the lower mountains. 



Nesting. — This subspecies usually nests on old hawks', eagles', 

 herons', and crows' nests 14 to 60 feet above ground. While the lower 

 body of the nest is neither added to nor even repaired by the owls, 

 there are times when they appear to add a few materials to the top 

 and build up a low rim to prevent the rolling away of the nearly round 

 eggs. As incubation advances, fur, bones, and a few feathers usually 

 collect. In places the Pacific horned owl makes her nest on ledges, 

 or in caves, of a rocky cliff. Sometimes a nest is put in a hollow in a 

 tree trunk, or where a limb has broken or rotted away. Occasionally 

 a nest is placed in a niche in a cutbank. Nesting begins as early as the 

 middle of January, especially in the lower altitudes. Since most of 

 California's lowland trees are along rivers, or about ponds and lakes, 

 there is at least an apparent grouping of the nests near water. Tyler 

 (1913) gives some interesting data: 



Among a clump of willows standing in three or four feet of water I found a pair 

 of Horned Owls nesting on April 12, 1902. They were occupying what may have 

 been an old nest of a Night Heron, a thin frail structure, placed fourteen feet above 

 the water. It measured six inches in width on the inside and nine in length, with 

 the cavity only two inches in depth; but it seemed ample for the great bird that 

 occupied it, and for her three eggs. * * * On April 6, 1906, I examined two 

 more nests of the same species within a mile of the first one discovered. One of 

 these nests was thirty-five feet up, in a partly -dead willow in a field. * * * The 

 other nest was eighteen feet up in a willow in a thick clump that, as in the first 

 instance cited, was growing in water. 



Nests as a rule are in oaks, live oaks, cottonwoods, willows, eucalyp- 

 tus, and sycamores. Apparently any tree that is tall enough and that 

 will hold a nest is acceptable. Nests are not always at the top but 

 sometimes as much as one- third of the way down. This subspecies 

 has also been known to make its nest, and rear its young, in the loft 

 of a ranch barn. Dixon (1914) has recorded of a pair: 



Toward the east end of the Escondido Valley, San Diego County, California, 

 there arises from the valley floor a steep and rocky ridge. On the eastern slope 

 of this ridge and in the big trees of the creek bottom directly beneath, two Pacific 

 Horned Owls (Bubo virginianus pacificus) have made their home for years. * * * 

 The edges of the small valleys and clearings are thickly populated with the smaller 

 mammals which make up the principal diet of the Horned Owl. * * * 



Records of nesting dates for this pair of birds are available for the past thirteen 

 years. During this time, to my knowledge, there have been killed in this imme- 

 diate vicinity four adult Horned Owls, but apparently the remaining bird had 

 very little trouble in securing a mate, as the site has never missed being occupied 

 for a single season. * * * This pair has nested in old hawk's nests in trees three 

 times, in an old hawk's or raven's nest in a cliff, twice, and in every other instance 

 has made its home on some rocky ledge on this steep hillside. 



