246 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



Purple Martins nesting in the boxes. Three days later, at twilight, I saw a gray 

 phase Screech Owl frequently alight at the entrance of a compartment of the larg- 

 est nest-box and quickly fly away after a very noisy reception from within. I 

 was surprised at this as Martins were nesting in all the other compartments. 



Investigation next day disclosed a husky young Screech Owl, apparently the 

 last of a brood, in the box. It was observed that the Martins carefully avoided 

 that compartment. Ten days later the Owl was gone and a pair of Martins at 

 once built a nest in and occupied that part of the box. 



By June 30 the Martins were all scouring the air and feeding their young. That 

 evening one parent Owl reappeared at the box. I scared it away but next day I 

 noticed that the two Martins that nested where the Owl had nested were not 

 feeding their young. A second inspection showed an empty nest. 



The screech owl also has been known to nest frequently, even 

 regularly, in cavities in trees close to houses in towns and cities, thus 

 showing more confidence in human beings than most other owls show. 

 1 have had several such cases reported in my home city. 



Eggs. — The screech owl lays three to seven eggs, but usually four 

 or five, with the average in favor of five; the extremely large or small 

 sets are rare; even as many as eight or nine have been reported, but 

 these reports seem doubtful. Bendire (1892) says that they "are 

 pure white in color, usually oval or nearly globular in shape, and 

 moderately glossy. In the majority of specimens the shell is smooth 

 and finely granulated, while in a few it is rough to the touch." The 

 measurements of 56 eggs in the United States National Museum 

 average 35.5 by 30 millimeters; the eggs showing the four extremes 

 measure 38 by 31, 37.5 by 32, 32 by 29.5, and 33 by 28.5 millimeters. 



Young. — The period of incubation is variously reported as from 21 

 to 30 days, but the average is probably around 26 days, as determined 

 by the careful observations of Miss Althea E. Sherman (1911). As 

 the eggs are laid at intervals of two or three days, sometimes at longer 

 intervals, and as incubation may begin after the first egg is laid, or 

 not until after two or three are laid, the exact period of incubation is 

 difficult to figure. 

 Apparently the female does most, if not all, of the incubating and the 

 brooding of the 3^oung. Miss Sherman (1911) describes the egg laying 

 and incubation as follows: 



The first egg was found in the nest on the morning of March 27, and was still 

 alone on the evening of the 29th. The following day the nest was not visited, 

 the only day in two months and a half, when visits were omitted. No doubt the 

 second egg was laid some time on the 30th of March; the third one was deposited 

 on April 1, but two days intervening between the laying of the second and third 

 eggs, while three or more days were the period between the other layings. The 

 fourth egg was in the nest at half past four o'clock in the afternoon of April 4, 

 but it was not there at eight o'clock on the previous evening. This shows that it 

 took from eight to nine days to complete the clutch of four eggs. Whether the 

 Owl laid in the night, or in the morning as other birds do, was not ascertained. 

 * * * Constant incubation appears to have begun on the first day of April 

 after which she was frightened out on two evenings. * * * Eggs No. 1 and 



