340 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



Enemies. — Although horned-owl nests are sometimes found with 

 eggs punctured and broken, and either crows or ravens may be the 

 culprits, there are so comparatively few crows in California that mob- 

 bing by them is not at all a common feature. Here, the owls are 

 sometimes mobbed by smaller birds. E. L. Smnner, Jr., writes us 

 about a Pacific horned owl nest: "There were linnets nesting in full 

 song, English sparrows present, and a pair of kingbirds, making a 

 perfect hubbub, but the owls were undisturbed in their midst until 

 the female owl flushed and perched in the tree, when the kingbirds 

 vociferated, orioles called, and the owl was actively attacked by the 

 former. The last I saw of the owl, when she took flight under the 

 attacks of the kingbirds as they clapped their bills with each dive, 

 was when she was flying straight away with the two kingbirds in hot 

 pursuit and one of them about to alight on her back." 



Huey (1913) says: "As the old bird left the nest (two miles down 

 the Sweetwater River from Dehesa) a pair of Red-bellied Hawks set 

 out in pursuit. One continued to chase the old owl, while the other 

 hawk returned and robbed the nest of one of the young owls. This 

 was torn to pieces and eaten in a nearby tree." A week later another 

 young owl had disappeared from this nest. 



It is conceivable that fly parasites may cause death among at least 

 the young owls. Stoner (1934) says: "I have been puzzled several 

 times when collecting eggs of the Pacific Horned Owl to find in the 

 nest many shiny black seed-like objects about the size of, or a little 

 larger than, grains of rice. These were especially evident in the loose 

 sand about the eggs when they are laid on the shelf of a cliff. They 

 had very much the appearance of seeds. * * * Mr. McAtee 

 kindly informed me that they were puparia of bird flies (Hippobos- 

 cidae). Large flat flies are often found on Owls and I suspect that 

 these are adults of these same 'seeds'." 



But man and his doings are the greatest destroyers of Pacific 

 horned owls. In addition to directly robbing nests and killing the 

 owls, man plows much ground and thereby destroys and drives away 

 rodents, the common food of western owls. He also chops down trees 

 and thereby decreases the number of nesting sites. Also, Grinnell 

 and Storer (1924) tell us that "Mr. Donald D. McLean says that a 

 horned owl taken 8 miles northeast of Coulterville was captured in a 

 rabbit snare on the ground. At Aspen Valley we found the mummified 

 remains of a horned owl impaled on a barbed wire fence. One wing 

 was broken and literally wrapped around the middle wire of the fence. 

 Evidently the owl had hit the fence while in flight and its struggles to 

 get free had but fixed its feathers more firmly on the barbs of the wire. 



Winter.— Hunt (1918) says: "On the night of January 29, 1918, a 

 Short-eared Owl was perched on a rock which crops from the steep 

 gravelly slope" on the campus at Berkeley. Suddenly the dark form 



