BIRDS OF NORTH AND MIDDLE AMERICA 65 



half is feathered. The extent and development of this feathering vary- 

 greatly with the season, being denser and longer in winter, when, in 

 Lagopus, the toes themselves are densely clothed with long feathers, while 

 iu the northern forms of Pedioecetes the feathers on the lower portion 

 of the tarsus are so long as to almost conceal the toes. The "purpose" 

 of this dense feathering of the feet seems to be to enable the birds to 

 walk more easily upon soft snow, the fringelike processes along the sides 

 of the toes in some genera possibly serving the same purpose, for in 

 summer, when there is no need of "snowshoes," the toes of Lagopus be- 

 come quite nude. At the same time the claws, which during winter are 

 large, broad, and concave beneath, like inverted spoons, are also shed.^* 

 The geographic range of the Tetraonidae embraces practically the en- 

 tire North Temperate Zone. North America possesses six peculiar 

 genera {Bonasa, Canachites, Dendragapus, Tympanuchus, Pedioecetes, 

 and Cc^ntrocercus), while the Palearctic Region has only four genera 

 {Tetrao, Urogallus, Falcipennis, and Tetrastes). One genus {Lagopus) 

 is circumpolar. Two of the Old World species {Tetrao lyrurus and 

 Urogallus urogallus) have been introduced into North America but seem 

 not to have become established. 



KEY TO THE GENERA OF TETRAONIDAE 



a. Tail decidedly shorter than wing, not graduated (or else middle rectrices 

 abruptly longer than rest and with rounded tips), rectrices rounded (some- 

 times nearly truncate) at tips; tarsus shorter than middle toe without claw; 

 feathers of neck without spiny shafts ; portion of culmen between feathered 

 nasal fossae less than half as long as apical portion; stomach a muscular 

 gizzard. 

 h. Tarsus with lower half (approximately) naked, scutellate; tail more than 

 two-thirds as long as wing. 

 c. Rectrices 18-20; sides of neck with a conspicuous erectile tuft of broad, 

 soft, decumbent feathers, capable of being expended into a ruff ; sexes 



aUke in coloration Bonasa (p. 153) 



cc. Rectrices 16; sides of neck without tufts or with these rudimentary; sexes 



different in coloration Tetrastes (extralimital)" 



&&. Tarsus densely feathered to or nearly to base of toes. 



c. Tail more or less forked (deeply emarginate to lyre-shaped) . 



Lyrurus (extralimital)" 



" See Stejneger, On the shedding of the claws in ptarmigans and allied birds. 

 Amer. Nat., xviii, 1884, 774-776. 



" Bonasia (not of Bonaparte, 1827) Kaup, Skizz. Entw.-Gesch. Eur. Tliierw., 

 1829, 193 (type, by monotypy and tautonymy, Tetrao bonasia Linnaeus). — Tetrastes 

 Keyserling and Blasius, Wirbelth. Eur., Ixix, 1840, 109, 200 (type, by monotj-py, 

 Tetrao bonasia Linnaeus). — Hartert, Vog. Pal. Fauna, iii, 1921, 1887. — Peters, Check- 

 list Birds of World, ii, 1934, 37. Palearctic Region (Europe to Kamchatka, Japan, 

 etc.). Two species with 10 subspecies. 



■^ Tetrao Linnaeus, Syst. Nat., ed. 10, i, 17S8, 159 (type, by subsequent designation, 

 Tetrao urogallus Linnaeus) (type, by tautonymy, according to Opinion 16 Intematl. 

 Nomencl. Comm., 1910, is Tetrao tetrix Linnaeus, but this is not accepted). — 



