FAMILY STRIGIDAE 1 55 



Amazon Valley. It is possible that the Pearl Islands birds may repre- 

 sent an undescribed form, but this should be determined when more 

 information is available. For the present it seems desirable to assign 

 them to the crucigerus group. 



It is probable that the ancestral birds of the Pearl Islands came to 

 that area during the Pleistocene at a time when lowered sea level 

 joined the present island group with the mainland. It should be 

 noted that the race luctisonus, widespread through Panama, also 

 occupies northwestern Colombia to the west of crucigerus. 



OTUS CLARKII Kelso and Kelso: Bare-shanked Screech Owl; 

 Buhito en Pernetas 



Figure 23 



Otus clarkii Leon Kelso and Estelle H. Kelso, Biol. Leaflet, no. 5, November 8, 

 1935, [p. 2]. (Calobre, Veraguas, Panama.) 



A small eared owl, larger than the other screech owls of Panama ; 

 only the upper two-thirds of the tarsus feathered, the lower section 

 and the toes being bare. 



Description. — Length 230-255 mm. Color as a whole warm brown 

 to brownish gray, varying from light to dark. Ruf escent phase : adult 

 (sexes alike), above cinnamon-brown to dull tawny brown; crown 

 with heavy shaft lines of black; elsewhere with black markings 

 mainly in the form of crossbars, connected in varying degree along 

 the line of the shaft ; hindneck with partly concealed markings of buff 

 that form an indefinite half -collar; rump and upper tail coverts 

 slightly paler than the back ; wing coverts, especially the primary 

 coverts, strongly black ; middle and greater coverts and scapulars 

 edged with white, forming prominent, broken streaks ; primaries and 

 secondaries fuscous, barred, mainly on the outer webs, with light 

 cinnamon-buff varied with white ; tail fuscous-black, barred nar- 

 rowly with cinnamon-buff ; ear tufts usually with a few spots of white 

 to buffy white; facial disk cinnamon-brown, with shaft lines and an 

 indefinite lower border of black ; chin white to buff ; lower surface 

 cinnamon-brown, with fairly definite black shaft streaks, irregular 

 narrow crossbars of black bordering the brown, and partly concealed 

 spots of white ; abdomen and under tail coverts paler than breast and 

 sides, from an increase in the extent of the white, which here forms 

 definite streaks; feathers of upper two-thirds of tarsus cinnamon- 

 buff, lightly barred with fuscous ; under wing coverts cinnamon-buff, 

 barred and lined with black ; under surface of wings fuscous, with 



