244 ADVENTURES AMONG BIRDS 



so that if two or more males of a brood, or family, sur- 

 vive to return to the same spot, one presently makes 

 himself master, and the other or others, driven away, 

 settle where they can, as near by as possible. It is 

 probably harder for the nightingale to go a mile away 

 from his true home, the very spot where he was hatched 

 and reared, than to fly away thousands of miles to his 

 wintering place in the autumn. The bird is exceed- 

 ingly reluctant to leave his home, but if the annual 

 increase was greater, a third greater let us say, more 

 and more birds would be compelled to go further 

 afield. They would go slowly, clinging to unsuitable 

 places near their cradle-home rather than go far, but 

 the continual pressure would tell in the end ; the best 

 places within the nightingale country, the ten thousand 

 oak and hazel copses and thickets which are now 

 untenanted, would be gradually occupied, and eventu- 

 ally the limits would be enlarged. That they cannot 

 be extended artificially we know from the experiments 

 in Scotland of Sir John Sinclair and of others in the 

 north of England, who procured nightingales' eggs 

 and had them placed in robins' nests. The young 

 were hatched and safely reared, and, as was expected, 

 disappeared in the autumn, but they never returned. 

 We can only assume that the *' inherited memory " of 

 its true home, which was not Scotland nor Yorkshire, 

 but where the egg was laid, was in every bird's brain 

 from the shell, that if it ever survived to return from 

 its far journey it came faithfully back to the very spot 

 where the egg had been taken. 



