3o6 THE BIOLOGY OF BIRDS 



some other birds of prey appear to give their young 

 ones lessons in flying and in the chase. The Great 

 Crested Grebe gets its youngsters on its back and dives, 

 thus forcing them to become at home in the water. It is 

 interesting to learn (Heinroth) that before ducklings leave 

 the nest the mother anoints their plumage copiously with the 

 oily secretion of the preen-gland, so that they are not wetted 

 when they take to swimming. Ducklings which have been 

 hatched out by a hen have not this advantage, but they learn 

 to attend to their foster-mother's calls, though this is not 

 natural for ducks. 



It is necessary to distinguish cases where the young birds 

 learn by association to attend to certain parental calls, from 

 cases where they require no instruction, but obey instinc- 

 tively without knowing why. Thus the young redshank 

 or the young partridge squats at a particular signal from its 

 parent ; and remains motionless until another call breaks 

 the instinctive spell. 



After the parent guillemots have fed and fondled their 

 single offspring for a month or so, the time comes for its 

 initiation to marine life. Before the young bird is able to 

 fly it may be jostled off the cliff-shelf into the sea, where it 

 is at first greatly embarrassed. But the first step is some- 

 times taken in a gentler way, for good observers have seen a 

 parent guillemot carrying its young one down to the water 

 on its back, and this is likely to be the case when the cliff is 

 several hundred feet high. A third method of initiation 

 is vouched for, that the parent sometimes seizes its offspring 

 by the neck and carries it down. In any case the young 

 guillemots have to be accustomed to the sea before the time 

 of migration comes, when restlessness seizes the myriads 

 and the cliffs know them no more for half a year. 



There are several points of great biological interest in 

 connection with the instruction given by parent animals to 

 their offspring, (i) It is the analogue of tradition and 

 education in mankind. It is a way of entailing gains that 

 do not form part of the organic or germ-plasmic inheritance. 

 (2) The clash of life against environing difficulties and 



