BIRDS IN THE CALENDAR 
answer, without any thought of irreverence, 
is " God knows ! " It is most certain that we, 
at any rate, do not. So far from explaining 
how it was that rooks came to build their 
nests in company, we cannot even guess how 
the majority of birds came to build nests at 
all, instead of remaining satisfied with the 
simpler plan of laying their eggs in the 
ground that is still good enough for the 
petrels, penguins, kingfishers, and many 
other kinds. Protection of the eggs from rain, 
frost, and natural enemies suggests itself as 
the object of the nest, but the last only would 
to some extent be furthered by the gregarious 
habit, and even so we have no clue as to why 
it should be any more necessary for rooks 
than for crows. To quote, as some writers do, 
the numerical superiority of rooks over ravens 
as evidence of the benefits of communal 
nesting is to ignore the long hostility of 
shepherds towards the latter birds on which 
centuries of persecution have told irreparably. 
Rooks, on the other hand, though also 
regarded in some parts of these islands as 
suspects, have never been harassed to the 
same extent ; and if anything in the nature 
50 
