308 MIND IN EVOLUTION CHAP. 



case may be. The mother cat is moved to lick and clean 

 her kittens as unthinkingly as they are moved to suck her. 

 When they pair, birds doubtless feel an impulse to build, 

 which the sudden gift of language would no more enable 

 them to explain than it would help to teach them the art 

 of nest-building. Nest-making, complex as it is, is mainly 

 the result of instinct. 1 Yet in these matters experience 

 also plays a part. Whether it is experience of the higher 

 or lower grade is difficult to determine. But when we find 

 that birds which have built their nests on the ground learn 

 on the introduction of cats into their island to move house 

 to the more salubrious quarters of the tree tops, we must 

 recognise that in animal behaviour there are well-developed 

 schemes of action in which intelligence has its share. 

 They are frequently modified by experience, and suitably 

 adapted to peculiar or to changed circumstances. They 

 are not instincts of the complex-mechanical type. Though 

 certainly not due to intelligence alone, they are not executed 

 altogether without intelligence. The adaptability of be- 

 haviour in the main based on heredity is well illustrated 

 in the case of nest-building. The oriole, according to Dr. 

 A. R. Wallace, 2 endeavours ordinarily to conceal its nest 

 from snakes and hawks, but in villages where it does not 

 fear these enemies, it builds openly. The orchard oriole 

 builds a shallow nest upon the stifFer branches, but upon 

 the slender twigs of the weeping willow builds deep, so 

 that the young may not be thrown out by the swaying of 

 the nest. The house sparrow, which makes a domed nest 

 in a tree, is content with loose building in a hole in thatch. 

 Schneider 3 states on the authority of Brehm that a tame 

 Cardinal finch which was bringing up a Cowbird, brought 

 it a cricket to eat. The nestling finding the insect too big, 

 the nurse tore and chewed the prey, and gave the softened 

 pieces to its charge. Many habits, which seem too complex 

 to be wholly due to intelligence, are nevertheless gradually 

 learnt. Thus, though the basis of nest-building is indubit- 



1 Dr. A. R. Wallace maintained the contrary view (Natural Selection, 

 p. \o et seq.\ but the evidence given by Mr. Lloyd Morgan (Habit and 

 Instinct, p. 232 et seq.} appears conclusive. 



2 Natural Selection, pp. 114, 115. Cf. Romanes, M.E.A., p. 210. 



3 P. 374 ; Brehm, IV. p. 373. 



