268 BRITISH BIRDS. 
many of the young birds pass southwards in the autumn, and never come 
back again : many die from the dangers of the journey ; and some probably 
settle elsewhere. The young of most birds rarely, if ever, remain in the 
locality of their birth. As soon as they reach maturity and can shift for 
themselves, the old birds, in a great number of instances, drive them off; 
whilst with some birds the movement is a voluntary one. Another cause 
which prevents the increase of our resident birds is the occurrence of hard 
winters. A long-continued frost or heavy fall of snow causes great mor- 
tality amongst small birds, of which any one may convince himself 
by noting the comparative abundance of birds in the beginnmg and 
towards the end of winter. The number of resident birds in a spring 
which follows a hard winter is generally conspicuously below the average. 
The general colour of the Robin is olive-brown, shading into buffish 
brown on the flanks and into greyish white on the centre of the belly; 
the forehead, lores, ear-coverts, chin, throat, and breast are rich orange- 
chestnut, the chestnut margined with a few grey feathers on the crown 
and the sides of the neck. Legs, toes, and claws pale brown; bill and 
irides black. The male and female birds are similar in colour. After the 
autumn moult the colour of the breast &c. is richer. Birds of the year 
scarcely differ from adults; but the young, in nestling-plumage, are 
spotted, caused by ochraceous centres and nearly biack tips to all the 
smaller feathers of the upper and under parts. 
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