THE OOLOGIST 



205 



allel the Ground Owl is migratory, 

 but here in Southern California he is 

 resident throughout the year from 

 the base of the mountains to the very 

 edge of the Pacific Ocean. The 

 breeding season is at its height in 

 Los Angeles County by the middle of 

 May. 



Every patch of pasture-land has one 

 or more pairs. On the grass-covered 

 slopes of Point Firmin above the 

 harbor of San Pedro I have found 

 them breeding in colonies of twenty 

 or more pairs. Here I have spent 

 many pleasant hours watching the 

 little fellows; and incidentally many 

 hours of hard labor digging for their 

 round white eggs. 



Some writers have it that the birds 

 excavate their own burrow, but I 

 have never found any evidence of 

 this, and believe that in the majority 

 of cases, if not invariably, they take 

 up quarters in the deserted burrows 

 of various small quadrupeds such as 

 ground squirrels, prairie dogs, and 

 rabbits. 



These holes are from four to ten 

 feet in length, and are of varying 

 shapes; some are straight while 

 others are driven in the shape of a 

 horse-shoe. From six to twelve 

 inches in diameter, the burrow wid- 

 ens out at the end into a small cham- 

 ber a foot or more across, and from 

 two to four feet below the surface of 

 the earth. 



The Burrowing Owl betrays his 

 nest by the quantity of dry horse 

 or cattle dung that lines it from the 

 entrance to the nesting chamber 

 proper; the latter being thickly car- 

 peted to a depth of two to four 

 inches with this material. Some- 

 times dry grass, rags, paper or what 

 ever other suitable substance may 

 be available is used. In the vicinity 

 of San Diego I once found a burrow 

 that was lined with cotton waste ob- 



tained from the nearby railroad 

 shops. 



The eggs are from five to eleven 

 in number, white in color as with all 

 the Owls; the average measurements 

 are 1.25 x 1.00 inches. They are ellip- 

 tical in shape, the ends being of an 

 equal size. I have often found eggs 

 lying on the ground near the en- 

 trance to the nest. These adventi- 

 tious eggs seem to be infertile in all 

 cases. As both the birds remain in 

 the burrow throughout the day in- 

 cubation starts with the first egg 

 laid, and a large set shows embryos 

 in all stages of development. No 

 doubt the dung used in the nest gives 

 out sufficient heat to maintain the 

 necessary temperature when the par- 

 ent birds are absent at night in 

 search of food. I have been unable 

 to learn from my own observation 

 how long incubation lasts, the under- 

 ground location of the nest making 

 studies of this sort difficult in the 

 extreme. Mrs. Wheelock in "Birds 

 of California" gives three weeks as 

 the time, which figure is doubtless 

 correct. 



When hunting in the early evening 

 the birds call to each other with a 

 short "too-oo," the last syllable rising 

 sharply. Another note resembles the 

 "kow-kow-kow" of the California 

 Cuckoo; this latter note is frequently 

 heard as a pair sits on the mound 

 outside their burrow, first one and 

 then the other uttering it as if carry- 

 ing on a conversation. 



All members of the Owl family 

 eject the undigestible portions of 

 their food from the crop in the shape 

 of pellets, and our Burrowing Owl is 

 no exception. These pellets are 

 found in large quantities scattered 

 along the length of the burrows; 

 they are composed of small bones, 

 fur, feather quills, wing cases of in- 

 sects, etc. The egg-collector can 



