492 BIRD BEHAVIOUR xvn. 2- 



bird to establish an effective routine for each part of its life, especially 

 as it is combined with the power to explore elsewhere when conditions 

 change. 



Food selection thus depends on species-characteristic motor patterns 

 and structures, whose use varies to suit the circumstances. There is an 

 initial responsiveness to a wide range of stimuli, later modified by 

 learning. In young birds these actions are not necessarily related to 

 appropriate objects or situations. Thus young chaffinches or tits peck 

 at spots of many sizes, but only when they are not hungry. When they 

 are, they beg from the parents. Young kestrels 'play' at hunting pine 

 cones, even after obtaining food by real hunting (see Hinde, 1959). 



This range of response is then narrowed by learning. Objects that 

 provide food are pecked again, those that do not or are distasteful are 

 avoided. The range of learning that is possible must, however, be 

 influenced by the hereditary equipment. Thus chaffinches never use 

 the foot to hold objects but goldfinches and tits do so and can thus 

 learn to pull over a grass stem and peck off insects otherwise out of 

 reach, or indeed to open milk bottles! 



3. Recognition and social behaviour 



Great mobility has made it necessary for birds to develop specific 

 means for recognizing their fellows, their enemies, and their com- 

 petitors; from this power an elaborate social life has developed in 

 many species. In spite of their freedom many birds are not indivi- 

 dualists, they live much of their lives together in flocks; the unit of 

 life is larger than the 'individual' body. Species feeding on the ground, 

 such as rooks, starlings, and partridges, commonly move about in 

 groups during the winter and obtain the advantage that the alertness 

 of each single bird serves to warn for many. The lack of procryptic 

 coloration in some of these social birds is a measure of the effectiveness 

 of the protection afforded by the society; indeed, it may be advanta- 

 geous that the birds should be conspicuous to their fellows. Starlings 

 carry the communal life farther by collecting together in large numbers 

 each night to roost. As many as 100,000 may be found in one roost, 

 the birds flying home from their feeding-grounds every night for 

 distances of many miles. Possibly in this way the disadvantage of the 

 conspicuous outline is minimized while roosting. Rooks show some- 

 what similar behaviour, but it is not found in the protectively coloured 

 partridge. 



Many different means are adopted by birds for recognition of other 

 members of the species and of the same and opposite sex; bird-life 



