5 ideas
Sustained, repeated attention to the commonest species (a pigeon, a dandelion, a garden spider) yields more real knowledge of nature than chasing rare sightings. Familiarity is what lets you notice change: you can only register that something is early, late, absent or behaving oddly if you have watched its ordinary pattern closely.
Treat the city as a living habitat rather than nature's opposite. Buddleia on railway sidings, weeds in pavement cracks, foxes, gulls and roosting birds show that wildlife colonises neglected urban margins. Meanwhile intensively farmed countryside can be a green but biologically impoverished desert, so 'rural' and 'natural' are not the same thing.
A fixed, short, recurring record of what is seen, such as a weekly column or diary entry, builds a baseline of attention over years. Because each note is small and dated, the accumulated entries turn scattered impressions into a record of seasonal timing and of year-to-year shifts that no single outing could reveal.
Absences can be read as data, as well as sightings: fewer insects on a windscreen, quieter summer evenings, thinner swift numbers overhead. Loss of common wildlife is hard to perceive because it happens gradually against a shifting baseline, so the observer has to deliberately register what is missing.
Harrison wrote her Times nature columns first from a rented flat in south London. There she recorded wildlife in parks, pavements and back gardens. She then moved to a village in rural Suffolk, where the columns turned to hedgerows, fields, rookeries and local weather, which let the same observer compare urban and rural nature directly across the seasons.