The dunnock, or hedge sparrow, is a common garden bird, a retiring little brown creature. Its pointed beak distinguishes it from the more perky (and unrelated) house sparrow, with its fatter seed-cracking bill. One warm March day I was sitting on our back steps when a tremor behind a shrub caught my eye. There, on an almost-hidden patch of bare soil, were two dunnocks: one was hunkered down, wings fluttering delicately near the ground, while the other circled around, dancing (if a bird can dance) at a respectful distance, encircling it once, twice... And then, perhaps because they spotted me, it was suddenly over.

I had seen something secretive and important, something powerful, something much weightier than the small bundles of feathers that had enacted it. I assume it was a courtship ritual, but I haven't met anyone who can confirm it, and the Internet has failed to divulge anything.

I have since learned, however, that dunnocks have an extraordinarily complicated family life: that a female may set up house with one or two males, and that males, likewise, may have one or two mates at the same time. It was a bit shocking to realise that the birds I had witnessed having a beautiful, private moment together may have been about to skip behind another shrub to have other private, beautiful moments with other partners. And all of this is going on in one's back garden!

Some people watch birds to collect "ticks" (each time they see a new species they mark it off on a checklist- they are known as "twitchers"). I'm not terribly concerned about ticks, which is just as well, as my collection is still in double figures - whereas Ireland's top "lister" has 383. You need to spend lots of time away from home to rack up that sort of score, and be willing to travel at short notice to add a rare passage migrant to your list.

I'm more interested in getting to know who's visiting my garden, and what they're doing when they get there. A surprising number of bird species pitch up in ordinary back gardens, especially between autumn and spring. Our Dún Laoghaire patch, for instance, has yielded up three dozen species over the past six or seven years, either as residents or as guests. And while I say I'm not that bothered about seeing rarities, I was as puffed up as a cock robin when a lesser whitethroat spent four months with us, hanging out with the sparrows.

Usually, this dapper little grey-and-white warbler overwinters in Saudi Arabia, India or northeast Africa. "Our" bird was the first to be recorded in winter in Dublin, and the third in the whole of Ireland. Yet rare birds such as this are no doubt touching down in domestic gardens without ever being recognised. If I hadn't been dogged about identifying every creature that visits us, it would have passed through unnoticed - and unrecorded. And perhaps if I didn't "manage" my garden with wildlife in mind, it would not have found it a congenial place to stop by.

The rare bird was a bonus, giving me unexpected (and brief) credibility amongst the twitching fraternity. But, just as exciting for me, was the first time a trio of multi-coloured goldfinches in their jolly jester plumage alighted on the teasels planted specifically to attract them. And equally thrilling was the first appearance of a troupe of five long-tailed tits, which flew one by one - urgently calling "tsee-tsee-tsee" - into the New Zealand hoheria outside my window.

The hoheria is an evergreen tree, so it offers much-needed shelter to our feathered friends in winter. It also supports a colony of aphids which provide essential protein for the tits and goldcrests that regularly forage here during the lean and chilly months.

Evergreen trees, shrubs and flowering perennials (such as penstemon, wallflower and aubrieta) are key elements in the bird-friendly garden. So also are berrying trees and shrubs, supplying valuable avian fuel to thrushes, blackbirds and blackcaps. Red berries are most attractive and will be eaten first, followed by orange ones, and then yellow.

Sparrows and finches eat mainly seeds, winkling them out from the spent flowerheads of border perennials (and weeds). Gardeners who tidy up meticulously in autumn are taking precious foodstuffs away from the birds. Even the leaf litter under trees and shrubs is important, as it harbours worms, insects, spiders and other creepy crawlies. These help to sustain the dunnocks, wrens, robins, blackbirds and thrushes that rustle in the undergrowth.

Birds are comfortable in a garden where the planting is arranged in layers, as at a woodland edge - with trees and shrubs giving away to herbaceous plants and grass. Even a tiny garden could have a mini-habitat: a single tree (birch, for instance, which has a light canopy and attracts lots of insects) underplanted with a shrub or two and some flowering perennials. Along with food and shelter, water is the final ingredient for the bird-lover's garden. A garden pond will bring birds in to drink and to bathe. One of the most delightful visitors to our tiny paddling-pool-sized pond was a female mallard who appeared one morning at 6 am recently. I had stepped outside to blearily greet the dawn, and I almost bumped into her plump, duck form. She didn't stay long - but long enough for me to look into her round, brown eye, and to be grateful for such a surprising start to the day.

Jane Power writes on gardening in The Irish Times Saturday Magazine.

Photo above: Jane Power keeps an eye on a sparrow in her garden in Dublin. Photograph: Frank Miller

Keeping a bird-friendly garden

• Stop using pesticides: birds need insects to feed on. There is also the possibility of indirectly poisoning them.

• Leave old seed heads on plants over winter, and don't be in a rush to clear up leaf litter under shrubs.

• Plant as diverse a range of plants as possible: trees, shrubs, herbaceous plants, grass. Make sure that some plants are evergreen.

• Include some native plants, as these support greater quantities of insects than introduced species.

• Offer different habitats, to attract a variety of birds

• Provide a bird bath, or a pond with sloped or stepped sides so that small birds can safely stand and flick water over themselves.

• In nature, birds use trees as lookout points and song perches. If you've no trees, supply substitutes such as trellis obelisks, bamboo wigwams, or simply a post banged into the ground with a sheaf of twigs tied to it.

• Set up a feeding station with nearby cover where birds can gather and fly out for food when they feel safe. But don't put it within cat-jumping distance of thick shrubs (about 2 metres).

• Stock feeders with lots of different foods, including seeds, peanuts and fat balls. Bread, cake, chopped pasta, rice, grated cheese and scraps of fat are also good stuff. Chopped apples strewn on the lawn attract thrushes. Never feed crisps, salted nuts or other salty foods. Don't let food go rotten or feeders get mouldy. Scrub down bird tables and wash out feeders regularly.

• In cold weather, provide food first thing in the morning. Small birds can lose a lot of body weight keeping warm at night, and they need to feed up fast.

PLANTS FOR SHELTER:

Most evergreens and conifers (but avoid the fast-growing and un-neighbourly Leyland's cypress); dense hedges and shrubs, including prickly species such as holly and pyracantha; ivy.

BERRYING SHRUBS, TREES AND CLIMBERS:

Cotoneaster, pyracantha, berberis, elder, crab apple, hawthorn, holly, rowan (and other Sorbus species), ivy and honeysuckle.

TREES FOR SEEDS AND FOR INSECTS:

Alder, beech, birch, oak and willow.

FLOWERING PLANTS:

Almost anything that sets seed will attract birds in autumn and winter. The following are especially popular: teasel, artichoke, sunflower, evening primrose, thistle and nettle.