YOU may not have noticed it, but there has been something of a revolution going on in your garden over the last thirty years or so. Where once you would look out of your window and see a host of sparrows, thrushes and starlings on your lawn or fluttering on your hedge - today the birds that occupy our gardens are very different with the robin, goldfinch and magpie now top of the pile.

The RSPB, which is just about to launch its Big Schools' Birdwatch on Tuesday and then its Big Garden Birdwatch later in the month, says the change is down to climate change and human behaviour, such as the use of pesticides and the expansion of towns and cities.

Scotland is now playing host to one little newcomer because of warmer weather - the nuthatch. The bird has been expanding through England over the last decade and is now gaining ground in southern Scotland. Over the coming years, the nuthatch will advance deeper into Scotland.

The RSPB's Martin Fowlie said: "They’ve traditionally been an English bird, but they’re becoming more common in the Borders and the Central Belt and, as we get a warmer climate, they will move northwards with that. In England they make use of garden feeders and that’s something that we may expect to see more of in the next 10 to 20 years in the south of Scotland."

The RSPB's birdwatching event, is the world's largest garden wildlife survey, has been integral in establishing the changes in our gardens.

Fowlie said the RSPB has noticed sparrows and starlings in particular "taking a massive tumble" in population numbers in the last 30 to 40 years.

"Some of the reasons for their decline, we know. Some of the reasons, we don't," he said. "With house sparrows, there’s a lot of debate about why they have decreased. They still appear in lots of gardens, but nowhere near as many as in our grandparents generation.

"The suspicion is during the breeding season, when they feed their babies on caterpillars and other insects, there’s less of them available.

"This is partly because we have brought things into our garden which are non-native plants and flowers, so that's not as good for British insects as traditional British plants."

Also in decline is the song thrush, because of less food available to them. "We’ve become much better at keeping our gardens tidy, using slug-pellets, that sort of thing. That means there’s less snails to feed on. Also, they like quite untidy areas of the garden to nest in. But we’re much tidier gardeners than we were thirty to forty years ago."

There are, however, birds which have been thriving in the changing environment, like the nuthatch.

"The Goldfinch - a beautiful little bird with a red, white and black face - has become really good at accessing the food that people put out for them. Robins are another. If you’re a gardener, chances are you’ll have a robin that comes and sits on your spade and watches you as you turn over your allotment veg patch.

"They’ve been really good at making use of they things that we do in our gardens. And the long-tailed tit. At this time of year you get them in flocks of ten to twenty. They’ve been really good at adapting to the food and seeds that people put out."

As for those divisive figures of the bird world - such as the pigeon and the magpie - despite thriving in the past few decades, they may have already reached their peak.

"Looking at the figures from last year, woodpigeons have decreased so it might be that they've done very well but they might not do much better," Fowlie said.

"It's the same with magpies as well. Incredibly clever birds, very good at adapting to new environments and they've done pretty well out of human habitation and food that they can get. But they're not having any affect on other species as far as we know.

"All the science says that the declines we're seeing across the board in our birds is down to lack of insects in terms of what we do, how we use our land, lack of habitat. As we expand our towns and cities, we start to eat into natural habitat and those are the things that are really affecting birds."

TOP TIPS ON GETTING BIRDS INTO YOUR GARDEN

A tidy garden can still be a wildlife-friendly garden, according to the RSPB. It is when gardeners become "too clinical" that it damages the habitat for birds.

A range of plants which flower and seed at varied times throughout the year will provide food for birds, as will insects that are active and feeding over different periods.

Ensure that plants are of genuine native stock and not from far flung places - birds like food which grows in the habitat in which they live.

Put out food for bird in feeders, but also think about planting flowers and plants which produce berries, and those which attract insects and moths.

Resist the urge to clear up at the end of the summer, as leaving seedheads standing provides a great food resource to many birds.

Leaving the dead plantheads standing also helps protect the soil beneath.

Be a wildlife-friendly gardener and avoid using pesticides, instead use non-toxic, non-chemical alternatives.