SAGUARO SCREECH OWL 283 



In naming and describing this race, Mr. Swarth (1910b) gives as 

 its characters: "Most like Otus asio cineraceus (Kidgway), from which 

 it differs chiefly in slightly smaller size, paler coloration and greater 

 restriction of dark markings. Above pale ashy, darkest on crown, 

 each feather faintly vermiculated with dusky, and with a narrow 

 dark median stripe. Under parts somewhat darker, but still with 

 dark markings much restricted. Legs and toes white, sparsely marked 

 with dusky." 



Nesting. — We spent May 21 and 22, 1922, exploring the dry, hot 

 saguaro plains near Tucson, Ariz. Here the arid, stony ground was 

 scantily covered with low mesquite and greasewood bushes, among 

 which the picturesque candelabra of the giant cactus, with their crowns 

 of white blossoms, were widely scattered. My husky companion, 

 Frank C. Willard, carried upright on his strong shoulders an 18-foot 

 ladder, with which we investigated the numerous cavities in these 

 strange plants. There were very few saguaros that did not contain 

 some of these nesting holes, and many had three or four. The holes 

 were, doubtless, all originally made by Gila woodpeckers and Mearns's 

 gilded flickers, which were very numerous here. These holes last for 

 many years, as the interior walls become crusted over and hardened, 

 making ideal nesting sites, after the woodpeckers have abandoned 

 them, for elf and screech owls, Arizona crested and ash-throated fly- 

 flycatchers, desert sparrow hawks, cactus wrens, and western martins. 

 Among all this interesting collection of nesting birds, we found two 

 families of saguaro screech owls, each with two young nearly half 

 grown, on May 21. The next day we saw evidence of overcrowding 

 in this thickly settled community of nesting birds; we saw an elf owl 

 looking out of one of these holes, but when we chopped it out, we were 

 surprised to find a screech owl sitting on three elf owl's eggs. 



So far as I can learn, the saguaro screech owl has never been found 

 nesting anywhere but in the giant cactus (Cereus giganteus), and only 

 where this cactus grows in the lowlands. Herbert Brown told Major 

 Bendire (1892) that he had found them "nesting in holes of sahuaras 

 within 4 feet from the ground, and from that distance up to almost the 

 extreme top of the plant. The sahuaras along the river bottoms, and 

 on the mesas bordering them, are their favorite nesting grounds." 

 He cut down a number of large saguaros in other places, at higher ele- 

 vations, that were bored full of woodpeckers' holes, but never found 

 any owls in any of them ; so he concluded that these owls nest only in 

 the saguaros "growing in the lowlands and not those in the higher hills 

 or out in the deserts." 



Eggs. — The saguaro screech owl lays three to four eggs. These are 

 like the eggs of other screech owls but smaller than those of the larger 

 races. The measurements of 11 eggs average 34.1 by 29 millimeters; 



