INDEX. 
Smell, sense of, 75 ; in vultures, 142. 
See Opor. 
Snakes, incubating, 97; nest build- 
ing, 105 ; swallowing their young, 
134; eaten by birds, 143; degen- 
erated from lizards, 146. 
Snipe, antics of, 71; shape of wing 
and skulking, 172 (ill., 173) ; feeding 
habits of, 187, 188. 
Snowbird. spots on young, 39 ; white 
tail feather conceal d, 56; con- 
sciously flitted, 57, 280. 
Soaring, wing for, 173 ; weight for, 
19. 
Social expressions, various, 56, 57 ; 
habits in migration, 181. 
Song, and battle, 65, 82; flight dur- 
ing, 72 ; came in with the birds, 77 ; 
and bipeds, 78; definition of. 79; 
position during, 80; and health or 
vigor, 81; rivalry in, 82; associa- 
tions of, 83 ; of migrants en route, 
86; revival of, in sammer, 87 ; and 
polygamy, 87; after bereavement, 
92 ; correlations of song muscles, 
primaries, and scales, 176, 195. 
Sparrows, bare tracts on, 23; Eng- 
lish, color of, by fraying, 42; and 
color calls on, 56; Peabody and 
white-crowned (ill.), 246. 
Spoonbill, 141. 
Spots, and stripes, on young, 39; on 
eggs, 121. 
Spun glass, nest of, 104. 
Spurs, on females, 50; on wing, 61, 
62; on most low bird’s ancestors, 
62; on leg in fowl forms only, 63 ; 
the spur’s limit upward, 145. 
Steel nest, 104. 
Step-parents (Chapter XV), 90. 
Stomach lost in parasites, 146. 
Sungrebe, kinship, 204. 
Swan, male devoted to young, 89; 
neck, 139 ; identifying, 216. 
Swifts, plumage tracts, 23; beak not 
a weapon, 60 ; cementing nest, 113 ; 
feeding young on wing, 133; feed- 
ing generally, 150; toe tendons of, 


261 
169 ; kinship of, 210 ; identification 
and toes, 227. 
Swimming, membranes for, 162; by 
wings, 139, 153 ; membranes shed 
by some amphibians, 164; birds 
generally, 214-217 ; toes lobed, 22 ; 
membranes vestigial, 222; with 
feet as rudders, 170. 
Syndactyle toes (see YOKE Togs), 162. 
Syrinx, dawn of, 77, 210. 
Tail, bones of, long in first birds, 9 ; 
its use now in flight, 9; feathers 
on, affecting plumage, 19; color 
ealls on, 55; feathers of, stiff, 199, 
202, 227. 
Talons, 222. 
Teeth, inherited, 59; lost and arti- 
ficial used, 136; notches in sea- 
ducks, 139, 202. 
Telescopes and migrants, 181. 
Tendons, of birds in sleep, 156, 157 ; 
of birds generally and of lizards, 
168 ; of Passeres, 210. 
Terns, playing, 69, 140. 
Tertiaries, elongated, 176. 
Thrashers feeding, 152. 
Thrushes, endowed for scolding, 82, 
83; feeding, 153; with best song 
muscles and sealeless shanks, 211: 
olive-backed, ways, 245, 246. 
Thumb, 10, 11. 
Tibia, 167. 
Tinamous, and feather tracts, downs 
on, 27; kinship, 202-204. 
Titmice, nesting, 101; notes on, 235, 
236. 
Toads (see Frog), skin secretions pro- 
tective, 63. 
Toes, of early birds. 10; rear, wanting 
in plovers, 138, 221, 222 ; outer, ver- 
satile in owls and ospreys, 143 ; 
yoked (see YOKE Toss), in cuckoos, 
parrots, ete., 147; rear, lost, 148, 
167 ; peculiar in Picaric, 151; in- 
ner, reversed, 151, 226 ; and armed 
in cassowary, 61 ; talk on (Chapter 
XXVIJ), 161 ; deficient in joints, 162 ; 
