6 BIRDS OF ILLINOIS. 



FAMILY TETRAONID^E. THE GROUSE, PARTRIDGES, AND 



QUAILS. 



CHAR. Hind toe small (much less lhan half as long as lateral toes), and inserted above 

 the level of the anterior toes. Tarsi without spurs. Head entirely feathered (in American 

 species) except, sometimes, over eyes. Tail not vaulted or arched, 



The following subfamilies of Tetraonidse have usually been 

 given full family rank, but almost without doubt are more 

 closely related. 



Tetraoninae. Tarsi with at least the upper half feathered; sides of toes with decidu- 

 ous comb-like pectinations (falling off in summer). 



Perdicinse. Tarsi entirely naked, and toes without pectinations at any season. 



SUBFAMILY TETRAONINJE. THE GROUSE. 



CHAR. Gallinaceous birds with the margins of the toes distinctly pectinated*, the tarsi 

 at least half feathered, the nasal fosste densely filled with feathers (so as to completely en- 

 close and partially conceal the nostril). Sides of neck often with an inflatable air-sac. A 

 bare (usually red or yellow) space over eyes. 



The Tetmonince are very strongly characterized among galli- 

 naceous birds by the peculiarities of structure named in the 

 above diagnosis. In addition, the following characters (not 

 always present) may be mentioned. 



The superciliary region is usually more or less bare, and some- 

 times (notably in the Ptarmigans) adorned with a comb-like, 

 or ciliated, erectile process, of a brilliant red or yellow color 

 during the breeding season. The tail is extremely variable in 

 development a,nd form, and may be either short and rounded 

 (as in Tympwnuchus and Lay op H.*), rather lengthened and fan- 

 shaped (as in Driul i'<j pn* and Bonasa), very short and grad- 

 uated, with the middle feathers lengthened and nearly truncate 

 ( Pf-dwccetex) , or considerably lengthened and much graduated, 

 with the feathers acute ( ('<'/<f /'<><< /<//*). Some genera have an in- 

 flatable air-sac on the side of the neck, while ornamental tufts 

 of feathers on the neck are possessed by others, Tympanuchus 

 and 



* These pectinations, however, are wanting in summer. 



