4 ideas
White argues that a naturalist who confines himself to one small district will add more to knowledge than one who surveys a whole country, because 'all nature is so full, that that district produces the greatest variety which is the most examined.' Apparent richness is a product of attention, not geography, so every parish or province needs its own dedicated 'monographer' watching it year after year.
Three small greenish leaf warblers, now called the chiffchaff, willow warbler and wood warbler, were treated as a single species until White told them apart in his letters to Pennant. He did it by their distinct songs, their habitats and their arrival dates at Selborne rather than by their near-identical plumage. It shows how repeated listening in one place can reveal distinctions that specimen-based naming had missed.
White calls earthworms 'a small and despicable link in the chain of Nature' that 'if lost, would make a lamentable chasm.' He explains the mechanism: they bore, drain and loosen the soil, drag in straw and leaves, and throw up casts that manure it. Without them the ground would turn cold, hard and barren. The unit is that the organisms doing the most essential work are often the ones that look least important.
White kept exact dates for the swallows' and martins' last autumn sightings and first spring returns, and he inclined toward the mistaken theory that some of them overwintered torpid in England rather than migrating. His dated observations stayed accurate and useful after the hypothesis failed. The lens is to judge a record by its fidelity and a theory by its survival, and to keep the two separate so that a wrong idea does not spoil good data.