26 DARWINISM chap. 



two or more broods a year, ten Avill be beloAv 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 we start with a single 

 pair, and these are allowed 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 A\ath ample vegetable and insect 

 food, but no other competing or destructive birds or quadrupeds 

 — their numbers would amount to more than twenty millions. 

 But we know A^ery Avell that our bird population is no greater, 

 on the average, noAV than it Avas ten years ago. Year by year 

 it may fluctuate a little according as the Avinters 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 eAadent they must 

 all die or be killed, somehoAv ; and as the increase is, on the 

 aA^erage, about five to one, it foUoAvs 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 we see nothing, or almost 

 nothing, of this tremendous slaughter of the innocents going 

 on all around us. In severe Avinters a feAV birds are found 

 dead, and a fcAv feathers or mangled remains shoAv us AA'here 

 a wood-pigeon or some other bird has been destroyed by a 

 haAvk, but no one AA'ould imagine that five times as many birds 

 as the total number in the country in early spring die CA^ery 

 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, AA'e 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 seA'ere, AA-ith 

 nestling birds, Avhich are often killed by heavy rains or blown 

 away by severe storms, or left to die of hunger if either of 



