FAMILY STRIGIDAE 1 53 



The localities cited above are based on specimens. In addition, I 

 have heard screech owls that I believed to be this species on Barro 

 Colorado Island, near El Uracillo, Code, and at the Quebrada 

 Venado near Armila, San Bias. The specimens from Juan Mina are 

 the only ones seen from the Caribbean drainage. The other reports 

 from that area are based on calls of birds heard at night, and so are 

 subject to verification. This race of Otus choliba ranges south into 

 western Colombia, where it is found near Unguia, Choco, a short dis- 

 tance beyond the Panamanian boundary. 



At present this is the best known of the three screech owls found 

 in Panama, and may be the most abundant in number of individuals. 

 It seems more adaptable than the other two, as in its main range in the 

 Pacific lowlands west of the Canal it appears able to adjust to shelter 

 in groves and thickets, and even in orchards as forest cover is cleared. 

 I have found them in tall hedge rows bordering pastures, and in 

 thickets of second growth adjacent to cultivated farms. At night I 

 have heard them calling regularly from scattered orange trees near 

 the small houses that have served me as temporary quarters. 



The call begins with a rippling trill, similar to that of the vermicu- 

 lated screech owl, but terminates in an abrupt, explosive whistle, some- 

 times uttered twice in rapid sequence, kao or kao, kao. This abrupt 

 note serves to identify the present species without question. The 

 birds are heard mainly in the evening at full dark, but may call at 

 intervals through the night. Sometimes they remain silent during 

 hours of bright moonlight, and on other such occasions are vocal. At a 

 distance the abrupt call at the end of the trill may resemble a barking 

 sound. 



On March 16, 1958, near Anton, Code, as I followed a cattle trail 

 beside a fence in woodland on the banks of the Rio Estancia, a small 

 owl flew out of a hole in a tree to hide in the adjacent undergrowth. I 

 stalked it and shot it to find that it was the present species. On exami- 

 nation of the hole I found that the bird had come from a nest that 

 held 2 eggs. The cavity, about 30 centimeters deep, was a natural one, 

 1^ meters from the ground in a fork of one of the quick-growing trees 

 that are cut for fence posts, and that regularly take root. The opening 

 was barely large enough for me to insert my hand. The eggs rested 

 on fine bits of decayed wood. In one incubation had begun, while the 

 other was recently laid. In form, one is rounded elliptical, the other 

 short subelliptical. Both are white, without gloss. They measure 

 34.0x29.5 and 34.9x28.4 mm. A nest found January 1, 1915, by 

 Hallinan (Auk, 1924, p. 312), on the trail between Culebra and 



