454 BIKDS OF ILLINOIS. 



In South America is found a third subgenus which may be dis- 

 tinguished from typical Accipiter as follows: 



Accipiter. Five outer primaries with inner webs emarginated; 

 fourth or fifth quill longest ; inner toe not reaching middle of second 

 joint of middle toe. 



Hieraspizias. Four outer primaries with inner webs emarginated ; 

 third or fourth quills longest ; inner toe reaching to or beyond middle 

 of second joint of middle toe. 



SUBGENUS Accipiter BEISSON. 



Accipiter BEISS. Orn. i, 17CO, 10. Type Falco nisus LINN. 

 Ifisus Cuv. Lemons Anat. Comp. i, tabl. ois. 1799. Same type. 



Cooperastur BP. Rev. et Mag. Zool. 1854. 638. Type Falco stanleyi Aui>..=.F. 

 cooperi BP. 



The species of this subgenus are generally of small size and 

 slender form ; but, with a graceful and apparently delicate structure 

 they combine remarkable strength and unsurpassed daring. They 

 differ from the species of Astur mainly in less robust organization. 

 The species are very numerous, and most plentiful within the tropi- 

 cal regions. The Old World possesses about thirty nominal species. 

 Tropical America has, so far as known, thirteen species, two of 

 which are peculiar to Cuba. (These the reader may find carefully 

 monographed in the Bulletin of the U. S. Geological and Geograph- 

 ical Survey of the Territories, Vol. II., No. 2, pp. 91-129.) 



The two North American species may be distinguished as follows : 



COMMON CHARACTERS. Adults. Above bluish slate or plumbeous, the tail with 

 darker cross-bands and narrowly tipped with whitish; lower parts white, barred or 

 transversely spotted with pinkish rufous or light brownish, the crissum plain white. 

 Young. Above grayish brown, the feathers bordered, more or less distinctly, with 

 rusty, and scapulars with large white spots, mostly concealed, however; tail-bands 

 more distinct than in the adults, the spaces between them browner; lower parts white, 

 sometimes tinged with buff (especially in younger individuals), longitudinally striped 

 with brownish or dusky. 



1. A. cooperi. Size large, the wing more than 8.50 Inches. Tail decidedly rounded. 

 Male: Wing. 8.85-9. 40; tail, 7.80-8.30. Female: Wing. 10. 00-11.00; tail, 10.00-10.50. 



2. A. velox. Size smaller, the wing usually less than 8 inches. Tail even, or (in adult 

 males) slightly emarginated. Male: Wing. 6.10-7. 10; tail, 5.80-6. 10. Female: Wing. 

 7.80-8.80; tail. 6.60-8. 20. 



