26 
DARWINISM 
CHAP. 
two or more broods a year, ten will be below the average of 
the year’s increase. Such birds as these often live from fifteen 
to twenty years in confinement, and we cannot suppose them to 
live shorter lives in a state of nature, if unmolested ; but to 
avoid possible exaggeration we will take only ten years as the 
average duration of their lives. Now, if Ave start Avitli a single 
pair, and these are alloAved to live and breed, unmolested, till 
they die at the end of ten years, — as they might do if turned 
loose into a good-sized island AA r ith ample vegetable and insect 
food, but no other competing or destructive birds or quadrupeds 
— their numbers Avould amount to more than tAventy millions. 
But Ave knoAv very Avell that our bird population is no greater, 
on the average, hoav than it Avas ten years ago. Year by year 
it may fluctuate a little according as the winters are more 
or less severe, or from other causes, but on the Avhole there is 
no increase. What, then, becomes of the enormous surplus 
population annually produced ? It is evident they must 
all die or be killed, somehow; and as the increase is, on the 
average, about five to one, it folloAVs that, if the average 
number of birds of all kinds in our islands is taken at ten 
millions — and this is probably far under the mark — then about 
fifty millions of birds, including eggs as possible birds, must 
annually die or be destroyed. Yet Ave see nothing, or almost 
nothing, of this tremendous slaughter of the innocents going 
on all around us. In severe winters a feAV birds are found 
dead, and a feAV feathers or mangled remains show us Avhere 
a Avood-pigeon or some other bird has been destroyed by a 
hawk, but no one would imagine that five times as many birds 
as the total number in the country in early spring die every 
year. No doubt a considerable proportion of these do not die 
here but during or after migration to other countries, but others 
Avhich are bred in distant countries come here, and thus 
balance the account. Again, as the average number of young 
produced is four or five times that of the parents, Ave ought to 
have at least five times as many birds in the country at the 
end of summer as at the beginning, and there is certainly 
no such enormous disproportion as this. The fact is, that the 
destruction commences, and is probably most severe, with 
nestling birds, which are often killed by heavy rains or blown 
away by severe storms, or left to die of hunger if either of 
