American Osprey 195 
itself ; tarsus and toes feathered, or at any rate covered 
with bristles ; hind toe jointed on the same level as the 
others. 
Key oF THE FAMILIES AND GENERA.* 
A. Claw of the middle toe serrate on the inside edge, middle and 
inner toes approximately equal (Aluconide). Aluco, p. 196. 
B. Claw of the middle toe not serrate ; middle toe always exceeding 
inner toe (Strigide). 
a. Ear-tufts present and generally conspicuous. 
at Large; wing over 14; tail nearly concealed below by the 
lengthened under tail-coverts. Bubo, p. 208: 
bt Medium; wing 10 to 12; tail-coverts not abnormally long ; 
toes feathered to the claws. Asio, p. 197: 
ct Small; wing under 8; toes bristly ornaked. Otus, p. 204. 
b. Ear-tufts absent. 
at Larger; wing over 12. 
a? Bill concealed by frontal feathers ; plumage chiefly white . 
Nyctea, p. 210. 
b? Bill yellow, not concealed ; plumage not white. 
Strix, p. 200. 
bt Medium; wing 6 to 8. 
a® Tarsus hardly exceeding the middle toe without claw; 
toes densely feathered. Cryptoglaux, p. 202. 
b? Tarsus about twice the length of the middle toe without 
claw; toes bristly, not feathered. Speotyto, p. 211. 
ct Small; wing under 4; nostrils well within the swollen cere ; 
toes bristly. Glaucidium, p. 213. 
Family ALUCONIDA, 
This family, containing the Barn-Owls, is distinguished 
externally from the other Owls by having the claw of 
the middle toe pectinate or serrated along its inner side, 
and the middle and inner toes about equal in length. 
Anatomically the sternum is entire — not notched 
posteriorly and the clavicles or furculum are anchylosed 
to the sternum. 
* The names of the families of most of the genera have been changed in accordance 
with the new A.O.U. Checklist. 
02 
