FAMILY STRIGIDAE I47 



The history of the order begins with several forms of the Eocene 

 epoch so that the group has a record of more than 50 million years. 



KEY TO SPECIES OF STRIGIDAE 



1. Head with distinct feather tufts in the form of horns, placed on either side 



of the crown 2 



Crown smoothly feathered, without projecting feather tufts 7 



2. Toes feathered nearly to the end of the distal joint 3 



Toes bare, without feathers 4 



3. Size large, wing more than 300 mm. ; prominently barred on lower surface, 



a mottled pattern above. 



Great horned owl, Bubo tnrginianus nwsembrinus, p. 162 

 Smaller, wing less than 250 mm., heavily streaked above and below. 



Striped owl, Rhinoptynx clamator forbesi, p. 180 



4. Size large, wing more than 250 mm. ; ear tufts very long, streaked broadly 



with buff or white Crested owl, Lophostrix cristata, p. 158 



Smaller, wing less than 200 mm. ; ear tufts short with mottled pattern like 

 rest of crown 5 



5. Ixjwer half or more of tarsus bare. 



Bare-shanked screech owl, Otus clarkii, p. 155 

 Tarsus feathered nearly to the toes 6 



6. Lower surface clearly streaked, with definitely marked crossbars ; underside 



of wing strongly barred Choliba screech owl, Otus choliba, p. 150 



Lower surface with less definite streaks, more of a mottled pattern ; under- 

 side of wing less definitely barred. 



Vermiculated screech owl, Otus guatemalae vermiculatus , p. 148 



7. Size large, wing more than 208 mm 8 



Size small, wing less than 200 mm 10 



8. Chest with a broad dark band ; lower breast and abdomen plain, or with a 



very few narrow dark bars. 



Spectacled owl, Pulsatrix pcrspicillata, p. 163 

 Lower surface heavily barred or streaked 9 



9. Breast, abdomen and sides buff to buffy white, heavily streaked. 



Mottled owl, Ciccaba virgata, p. 174 

 Lower surface white, heavily barred with black. 



Black-and-white owl, Ciccaba nigrolineata, p. 178 



10. Legs slender, long, sparsely feathered, extending beyond end of tail ; a 



terrestrial species Burrowing owl, Speotyto cunicitlaria hypugaea, p. 173 



Legs relatively strong, short, heavily feathered, not reaching to end of tail ; 

 arboreal species 11 



11. Larger, wing more than 130 mm.; coloration plain, without streaks or bars 



above or below. 



Central American saw-whet owl, Aegolius ridgwayi ridgzvayi, p. 183 

 Smaller, wing less than 100 mm.; more or less streaked, spotted or barred 

 12 



12. Crown with definite longitudinal streaks, in some restricted mainly to the 



forehead. 



Ferruginous pygmy owl, Glaucidium brasilianum ridgwayi, p. 171 

 Crown marked with many small spots 13 



