dge-Sparrow, 213, 221, 244

Hereditary equipment, 6

Herring-Gull, 210, 278

Hooded-Crow, 202

Hostility and territory, relationship between, 242

House-Sparrow, 218

Imitation, vocal, powers of, 156, 157, 161

Impulse, internal, 279

---- to brood, 191

Inherited disposition, 5

Instinct, fighting, 79-82

---- gregarious, 20, 61, 141, 265, 266, 269, 276, 289, 290, 291, 296,
300

---- migratory, 37

---- of song related to establishment of territory, 125

---- sexual, reawakening of, 4, 18

Instinctive response, 180

Instincts susceptible to stimulation, 259

Internal impulse, 279

Internal stimulation, 62, 123

Interpretation of battles, 75

Intolerance of other birds, 218, 219

Intrusion resented, 274

Isolation, impulse to seek, 288

---- of male, 12, 62, 65, 73, 81

---- of male during breeding season, 267, 272, 273, 275, 281

Jay, 87, 156, 283

Kestrel, 228

Kittiwake, 116, 200, 247

Lapwing, 58, 59, 61, 62, 64, 84, 103, 104, 126, 189, 190, 220, 251, 284

Lapwing, life-history of, 58-61

Late arrival, advantages and disadvantages of, 33-44

Law of battle, 74, 75, 86

Lesser Whitethroat, 230, 244

Linnet, 156

M'Dougall, Dr, _Social Psychology_, 77

Magpie, 219, 283

Males arrive before advent of females, 24

Marsh-Warbler, 39, 40, 52, 81, 132, 140, 153, 155, 156, 165, 225

Martin, 201, 218

Mating, difficulties of, 172

---- fortuitous, 174

Maximum number supportable in a given locality, 49

Meadow-Pipit, 188

Meeting places for antics, 54, 63

Mental Image, 77

Merlin, 227

Migration, 3-4

---- distance no criterion, 279

---- its relation to territory, 259

Migration, origin of, 260, 277

---- phenomenon of, 277

Migratory instinct, 37

---- species more highly specialised than resident species, 56

Missel-Thrush, 21

Mobility of the land and stability of the water, 260

Moor-hen, 61, 85, 103, 218, 250, 251

Morgan, Professor Lloyd, on instinctive behaviour, 74

---- on emotional behaviour, 114

Nest, cleaning of, 180

---- construction of, 3

Nests, removal of, for experiments, 181, 185, 190, 213, 214

Neutral feeding grounds, 62, 125

---- ground, 98

Newton, E., on the arrival at breeding stations of males before female,
24, 35

Nightingale, 39, 156

Notes of alar