---- attainment of, 2, 6, 37 ---- goal of, 6 Ringed Guillemot, 64 Robbery of territory, 104-107 Rock-formation, suitability for Guillemots nesting on, 196 Rook, 202, 227 Routine behaviour, 262 Ruff, 54, 63, 172 ---- meeting places for conflicts, 54 Ruffs, promiscuous pairing of, 172 Savi's Warbler, 139 Sedge-Warbler, 25, 44, 152, 226, 244 Selous, E., on the life-history of Ruffs and Reeves, 172 ---- on meeting places for conflicts and antics, 54 ---- on the meeting places of Black Grouse, 63 Service, Robert, on flocks of unmated Sedge-Warblers, 44, 45 Sexual behaviour, 3 ---- conflicts, 10 ---- development, 6 ---- function, discharge of, 2, 3, 26 ---- impulse of females, 13 Sexual instinct in the migratory male, 26 ---- of Reeve, 173 ---- ---- reawakening of, 4, 18 ---- life of birds, 1 ---- maturity, males arrive at, before females, 36 ---- organic change, 92, 123 ---- selection, 166 Shag, 121 Shrike, Red-backed, 39, 50, 51, 156 Skylark, 188, 236, 244 Snipe, 153, 156, 219, 220 Sociability when not paired, 125, 126 Song, as an aid in searching for a mate, 12 ---- its influence on mating, 167 ---- origin of, 138 ---- relation to reproduction, 123 ---- relation to territory, 119-168 ---- volume of, influenced by age, seasonal sexual development, or isolation, 166 Song-Thrush, 222, 244 Sparrow, House, 218 Sparrow-Hawk, 269 Spring, at approach of, birds lose their shyness, 138 Stability of the water and mobility of the land, 260 Starling, 217, 218, 237, 251 Stimulation, internal, 62, 123 ---- question of, 284 Stonechat, 87 187, 188, 189, 222, 233, 234 Stout, Dr, _Manual of Psychology_, 1, 77 Struggle for existence, 294 Susceptibility to position, 96 Swallow, 21, 156, 278 Territory, 1, 5 ---- adjustment of, 10 Territory and reproduction, 169-214 ---- breeding, 2, 3, 7 ---- dates of acquisition of, 33 ---- defence of, 6 ---- desertion of, after rearing young, 276 ---- disposition to defend, 73-118 ---- disposition to secure, 6, 20-72 ---- establishment of, 74, 285 ---- evolution of, 176 ---- failure to secure, 286 ---- fights for, 10, 11, 13, 62 ---- ownership of, 189 ---- possession of, a stimulus to song, 136 ---- its relation to migration, 259 ---- its relation to reproduction, 169-214 ---- readjustment of, 147 ---- restriction of, advantageous for mating, 172 ---- restricted, 8, 9, 30, 50, 58, 64 ---- separate for male and female Cuckoo, 144 ---- song, its relation to the, 119-68 ---- temporary desertion of, 28, 35, 58, 59 ---- and hostility, relationship between, 242 Thrush, Song, 222, 244 Tit, Blue, 221, 226 ---- Great, 221 ---- Long-tailed, 226 Tradition, 300 Tree-Pipit, 51, 188, 189, 222, 232, 244, 278 Turtle-Dove, 126, 232 Union of sexes, 12