442 BIRDS OF ILLINOIS. 



A. Wing less than 18 inches; inner webs of not more than four ot five outer quills dis- 

 tinctly emarginated. 

 a'. Lower half, or more, of tarsi naked. 



b'. Front of tarsi without transverse soutellse. 



1. Elanoides. Tail excessively forked, the lateral rectrices more than twice 

 as long as the middle pair. Claws grooved beneath. Tarsi covered with 

 large, irregular scales. 



2. Elanus. Tail double-rounded. Claws rounded on their under side. Tarsi 

 covered with minute roundish scales. 



I'. Front of tarsi with transverse scutellce. 



ci. Tail emarginate. and bill greatly hooked or else distinctly notched and 

 toothed. 



3. Ictinia. Bill Falcon-like, with distinct, though not prominent, notch 

 and teeth. Feet small and robust, the claws not unusually elongated. 



4. Sostrhamus. Bill very slender and greatly hooked, entirely devoid of 

 notch or tooth. Feet slender, the claws unusually lengthened. (Ex- 

 tralimital; tropical.) 



C-. Tail truncate or rounded, or if emarginate the bill neither greatly hooked 



nor distinctly notched. 

 d'. Form slender, the head proportionally small, the legs slender, claws 

 very acute, and tail lengthened. Bill comparatively weak, com- 

 pressed, high through the base, the culmen much ascending 

 basally, and the cere decidedly arched. 



£. Circus. Face surrounded by a "ruff" of stiffened, differently formed, 

 feathers, as in the owls. Tarsus more than twice as long as the 

 middle toe. Wing very long, outer four primaries with inner webs 

 sinnated. 



6. Acoipiter^ Face without ruff. Tarsus less than twice the length of 

 the middle toe. Wing short, very concave beneath, the outer CLuill 

 much bowed, the five outer with inner webs emarginated. 



eP. Form short and heavy, the head larger, tail shorter, and legs more 

 robust, with claws less acute. Bill stronger, less compressed, 

 lower through the base, the upper outline less ascending basally, 

 and cere less arched. 



7. Parabuteo. Form heavy, the wings and tail moderately long, and 

 feet very robust; bill rather elongated, the commissural lobe 

 prominent, and the base of the culmen somewhat depressed. 



. Fourth quill longest; outerflve with innerwebscut. Lores naked, 

 and almost destitute of bristles. (Extralimital.) 



8. Onychotes. Outstretched feet reaching beyond end of tail; tibial 

 plumes short, close, not reaching below the joint. Wing short, 

 rounded, very concave beneath, the fourth quill longest; outer five 

 with inner webs sinuated. Tail short, but little more than half the 

 wing, slightly rounded. Claws very long and extremely acute. 

 (Extralimital.) 



9. Asturina. Bill and feet as in Parabuteo; lores densely bristled; 

 wing short, rounded, concave beneath, the third to fourth quills 

 longest; outer four with their inner webs cut. 



10. Buteo. FormofParaftttieo, but primaries longer and more pointed, 

 the fourth usually longest, and the outer three or four with inner 

 webs cut. Tail moderate, or rather short, nearly even, or slightly 

 rounded. 

 a'. Tarsus densely feathered to the base of the toes. 



11. Archibuteo. Feathering of the tarsus interrupted behind byabare strip 

 along the full length. Nostril broadly oval, obliquely horizontal; bill 

 weak, the upper outline of the cere much ascending basally. Feathers of 

 the nape normal, blended. ThircJ to fourth quiUs longest; outer four or 

 live with inner webs out. 



