10 
MIGRATION OF BIRDS. 
skylark of the summer, overflowing with happiness and 
complacency, and half bursting with song ! 
The Ring Ousel is another bird of passage that visits 
us with the greatest regularity in spring and autumn ; but 
our winter is too cold for him, I suppose, for he never stays 
above three weeks in autumn, then passing southwards 
towards the Sussex coast : in the spring his stay is still 
shorter, as he is then in a hurry to get to his home among 
the hills of the north, where he nestles. Hindhead is the 
resting-place of the ring ousel on both his passages, and 
he keeps about the tops of the hills. Stragglers have been 
shot at Rodborough and on Highdown's Ball, but this is a 
rare occurrence. 
The migration of birds is a study in which our ornitho- 
logists have not yet made any great progress. White and 
Bewick have touched on it, but not quite satisfactorily ; 
they point to migration as a kind of a tree of knowledge, 
whose produce, as that of the old one, is forbidden fruit. 
Now migration is the simplest thing in the world. At cer- 
tain periods of the year the proper food of certain species 
of birds fails in the native countries of those species ; this 
is the ^ cause' of migration: then the first 'law' of migration 
is the 'instinctive — and perhaps in some instances experi- 
mental — knowledge that proper food is about to fail.' The 
next important facts are, that the great mass of birds of 
passage are insect-eaters, and secondly, that insects, at the 
approach of winter, disappear first from the most north- 
erly countries : if water-birds or waders, still the facts 
obtain ; the freezing of lakes, rivers and mud-banks first 
occurs in the higher latitudes : hence the second law, that 
' migration is in a southward direction.' Thus, migration 
begins in autumn and goes on till winter, keeping pace 
