INDEX 



435 



Riddle, Prof. O., experiments in sex- 

 determination, 237 



River, birds of, 158 



Rock-dove (Columba liv^ia), pigeon- 

 ancestor, 366 



Rook (Corvus frugilegus), food of, 

 88-9, 401 ; community life 

 of, 316 ; intelligence of, 343 ; 

 economic aspect, 401 



RufT {Machetes pugtiax), courtship 

 behaviour, 187 sqq. 



Running before flying, 2, 71 



Running Bird type, 11 ; skeletal 

 form, 49, 51 sqq. 



Sailing flight, 78 



Sand-grouse (spp.), foot-form, 149, 



Seed-dispersal, by birds, 403-4 



Scales, characteristics of, 14 



Scent, suppression of, in sitting 

 bird, 290 



Scissor-bill (Rhyncops), form of 

 bill, 12, 94, 95 



Sea-clifFs, birds of, 154 sqq. 



Secretin, properties of, 139 



Selection, processes of, 383 sqq. 



Selous, E., observations on bird- 

 courtship, 184 sqq. 



Sense organs, 330-1 



Sex-cells ; see Germ-cells. 



Sex-characters, general, 206 sqq. ; 

 in birds, 210 sqq. ; masculine, 

 problem of transmission, 222 ; 

 suggested theory of origin, 

 223 sqq. ; in individual 

 development, 227 ; and 

 hormones, 228 sqq. 



Sex, differences, classification, 206 

 sqq. ; and specific charac- 

 ters, 218 sqq.; determining 

 factors, 233 sqq. ; Prof. 

 Riddle's experiments, 237 

 sqq. ; Mendelian view, 241 



Sex-intergrades, 178, 222 



Sex manifestations, 177 sqq. 



Sexual selection. Darwinian theory, 

 reconsidered, 198 sqq. 



Shag (Phalacrocorax graculus), diving 

 of, 86 ; seasonal characters, 

 220 



Shape, main types, 11 



Shearwater, Manx {Puffinus anglorum) 

 flight of, 85 



Sheldrake {Tadorna cornuta), di- 

 morphism, 211 ; nest of, 297 



Shoveller Duck (Spatula clypeata), 

 form of bill, 94 



Skeleton ; see Bones. 



Skin, 12 sqq. 



Skull, adaptations and structure, 62 



sqq-, 347-8 



Snipe, Common (Gallinago gallin- 

 ago), egg of, 272-3 ; adapta- 

 tion for feeding, 91 

 Painted {Rhynchcea capensis) , 

 sex-characters, 208 



Social life of birds, 314 sqq. 



Song, general character, 8 ; evolu- 

 tion of, 1 90-1, 206 ; variety, 

 191-2 ; song-box (syrinx), 

 193-4 ; interpretation of, 

 195 sqq. ; hereditary aspect, 

 195 ; imitative aspect, 196 ; 

 second periods of, 197 



Song-box, structure, 124 sqq. 



Sparrow, House {Passer domes ttats), 

 variability, 383 ; economic 

 aspect, 411, 413 



Sparrow Hawk (Accipiter nisus), form 

 of ovary, 245 



Spleen, functions of, 135 



Spur (carpal) in birds, 219 



Starling {Sturnus vulgaris), economic 

 aspect, 401, 413 



Sterility, 284 sqq. 



Stone Curlew {CEdicnemus crepitans), 

 cry of, 192 ; nest of, 296 



Sugar-bird (Coereba), variations, 

 372 



Swallow {Hirundo rustica), migration 

 of, 163, 164 ; nest of, 298 



Swamps, adaptation (of legs) to, 149 



Swan (Cygnus, spp.), egg of, 271 



Swift (Cypselus apus), migration of, 

 163 

 Sea-swift (Collocalia), edible 

 nest of, 298-9 



Syrinx, structure of, 124 sqq., 193-4; 

 as sex-character, 195, 223 



Tactile feathers, 21 



Tail, forms and uses of, 56, 68, 

 73-4; (of woodpeckers), 144 



Tailor-bird (Orthotomus), nest- 

 making, 295 



Tanager, scarlet {Piranga erythro- 

 melas), moulting of, 32 

 (Procnias), dimorphism, 212 



Taste, sense of, 332 



Teeth of ancestral birds, 15, 346 ; 

 absence of, in birds, 63 ; see 

 Egg-tooth. 



Teleoptiles, 22 



Temperature, 2, 5 ; see Warm- 

 blocdedness. 



