ANOTHER LIFE: When my eyes wander off to the goldfinches at the peanuts, just a cat's leap from my computer, I have to admit that feeding the birds is almost totally selfish. The sheer aesthetic pleasure of having half-a-dozen of these finches, brilliant as parakeets, in daily attendance just outside the window (even, blurrily, in wind and rain), far outweighs my dutiful concern for their welfare.
Like the blue tits who, half a century ago, suddenly discovered ways to get at the cream at the top of milk bottles by pecking a hole in the caps, goldfinches, siskins and blackcaps have discovered peanut takeaways once monopolised by strictly "garden" birds. They are helping to boost a bird-feeding industry which, in Britain, is now worth more than £120 million a year, and rising annually by a striking 20 per cent.
Gratified by greedy birds, many people decide in spring (last autumn would have been better) to reshape the garden for wildlife by digging a pond, planting a wild hedge, sowing a wildflower meadow. As cities spread and the bungalow ribbons join up, such gestures towards dispossessed wildlife become quite compelling.
The chief human reward of wildlife gardening, apart from sheer pleasure, lies in family education and solidarity with nature. But how much value has it, really, for wildlife itself?
Compared with the same square footage of bleak, over-fertilised silage sward on a beef farm in Co Kildare, a suburban Dublin garden with a native tree or two, plenty of good ground cover, a wide variety of plants chosen for nectar-filled flowers and autumn berries, and a regime that does without pesticides and herbicides must rate highly as a habitat this side of Eden.
Even as an island in a lawn-and-roses suburb, its value to insects and birds is very positive, since most of its wildlife will be gathered in from the air. But for real biodiversity, a location among mature gardens, perhaps with an orchard or two, or near mature parks or hedgerows, will greatly improve the flow.
In Britain, where 20 years or so of widespread wildlife gardening now merit ecological assessment, the best-documented single garden is still one on a busy suburban corner in Leicester, monitored in detail for 14 years.Some 2,200 species were recorded there, including 21 kinds of butterfly, 263 species of moth, 91 hoverflies and 94 plants that arrived of their own accord. These are impressive totals, even allowing for England's superior diversity of species, but they also remind us how little we know of the natural world around us.
As permanent ponds disappear from farmland, those of gardens are becoming a very real refuge for wetland insects and amphibians. Many will arrive by themselves (even the great diving beetle, Dytiscus, is an excellent flier), though priming with a spadeful of lake-bottom, full of invertebrate eggs and larvae, and a mugful of frogspawn will often help things on.
A successful pond has some dense cover to conceal the comings and goings.
Newts actually breed more successfully in garden ponds than out in the "wild" countryside, especially where a log-pile is left nearby to rot and give them shelter. But they will not thrive at all in ponds with fish, which eat their tadpoles.
How likely mammals are to visit or adopt a wildlife garden depends quite a lot on location. An exception is the fox, whose city life may have a home range of up to 90 hectares - the size of a big farm - and crossing many roads in its circuit of bird tables, dog's dishes, compost heaps and dustbins.
A hedgehog may also roam for hours, but less boldly and with no territorial intent or set plan of foraging. It goes where its nose takes it, pushing through slug-rich and beetle-bustling undergrowth. A bowl of dogfood, put close to a wall and cat-proofed (by an upturned wire basket with a small arch cut in it) may add to the residential attractions of a garden with plenty of thick hedges and shrubs.
Britain's Mammal Society quizzed householders about their gardens and found sightings of hedgehogs in 70 per cent of them, with mice and grey squirrels well ahead of that and foxes and bats close behind. Its researchers used "a backward-stepwise multiple binary logistic regression" on the figures (I had to share that) to confirm that wildlife gardening, with its nesting boxes for birds, bats and hedgehogs, its compost heap, pond and woodpile, is good for a wide range of species.
For some of them, a single sympathetic garden may be of limited value.
When a farm is sold for greenfield housing, it is likely to end up in separate plots of no more than 450 square metres, including house, patio and driveway. The foraging range of a field mouse is at least 1,000 square metres and even a fairly sedentary female hedgehog will often travel 500 metres in a night. Such mobile species need the proximity of woods or railway banks, or a complex of mature gardens with old orchards.
Indeed, most wild species use gardens as service-stations, offering food, shelter and perhaps a refuge from predators such as badgers and foxes. They rarely reach the same densities as in the countryside, unless gardens have something special to offer. When "wild" nectar is scarce in a drought, the well-watered flowers of gardens will attract hoverflies and butterflies; and early garden flowers such as aubrietia can supplement the diet of queen bumblebees emerging from hibernation.
Gardens, however nature-friendly, will never be a substitute for habitats lost from the wild: most ecosystems are far too complex or particular to be reproduced on garden scale, if at all. But wildlife gardens can create a mosaic of support and refuge for nature, and help to keep its wider needs high on the human agenda.