They Knew in 1862
I bought some old Punch magazines at an estate sale, and in reading through them, I have found interesting editorials and repeated pleas for people to stop killing birds, if for no other reason than that birds prevent insects from eating the crops.
Farmers Killing Their Friends
Farmers and gardeners will gape and stare when they come to learn the fact that grubs and caterpillars are now doing immense mischief in many places and especially in the neighborhood of Liverpool, all because the fools who cultivate the soil have had nearly all the little birds killed that would have kept them under….Our clodhoppers labour under a sad mistake in supposing that small birds live chiefly upon fruit and grain, thus consuming large quantities of human food. The grub which they eat most of is not good for man; it is a maggot, and a noxious one, which devours an amount of produce very much exceeding their [the birds] little pickings. The bushels of corn, currents, raspberries, and cherries which used to be swallowed by them, are few in number compared to the bushels of caterpillars which abound in consequence of their destruction.
Punch, June 14, 1862
I cannot find this issue of Punch online to link to. Both of the editorials I have quoted from were much longer, and by our standards, full of political incorrectness, but I think it’s interesting that people were writing about the importance of conservation so long ago.