This weekend you can take part in the biggest wildlife survey in the world - without ever leaving your garden. STEPHEN LEWIS reports on the Big Garden Birdwatch

DO you love the BBC's Winterwatch and Springwatch programmes? And have you ever fancied yourself as a bit of a naturalist?

Well, now is your chance to take part in what is said to be the world's biggest wildlife survey. And you can do it without ever leaving your garden...

This weekend (in fact, for three days from Saturday to Monday) almost half a million people across the country are expected to take part in the RSPB's annual Big Garden Birdwatch.

You don't need to spend all three days monitoring the wild birds which come to your garden - or even one day. All that is needed is for you to make a note of the birds which visit your garden (or your local park, if you'd prefer) in one particular hour over the course of the three days, then send your count to the RSPB.

The results of all those observations will then be gathered together to give an unrivalled picture of just what is happening to Britain's wild birds.

This will be the 39th Big Garden Birdwatch. And surveys in previous years have enabled us to understand the ways in which bird populations are changing, says Chris Collett, the RSPB spokesman for the north of England.

Some of our common wild bird species are doing very well - birds like the blue tit, blackbird, chaffinch, goldfinch and wood pigeon.

Others, however, have seen their numbers collapse since the first Big garden Birdwatch in 1979. The number of starlings has dropped by almost 80 per cent since the first Garden Birdwatch in 1979, Chris says - while greenfinch numbers have fallen by almost 60 per cent.

We still don't fully understand why - although scientists at the University of York found evidence that Prozac and other antidepressants which make their way into the water supply could be affecting starlings.

The drugs are taken up by earthworms which live in sewage. The worms are then eaten by starlings - and the drugs build up in the birds' blood, affecting their appetite and their libido, the researchers found.

Whatever the reasons, the first step in being able to do something about falling wild bird numbers is establishing that there is a problem, says Chris. By establishing which birds are increasing and which are decreasing in numbers, the Big Garden Birdwatch helps us do exactly that. "It is extremely valuable information," Chris says.

So how do you take part?

Set aside one hour this coming weekend to keep a watch out in your garden or local park.

Make a note only of birds which land in your ga5rden or in the park, Chris says. Don't count individual birds - the same bird might come, fly away, then return, so you could end up counting the same bird over and over again.

Instead, make a note of the maximum number of each type of bird which lands in your garden during your hour of observing, then send your observations to the RSPB. TYou can get a free Big Garden Birdwatch pack which will enable you to do this from the RSPB at www.rspb.org.uk/birdwatch

If you're not confident in your ability to recognise different species of birds, the RSPB website has a handy bird identifier which should help you. And if you're really not sure what a bird is, you can always take a photo and tweet it to the RSPB at @natures_voice, where someone will be able to identify it.

"You never know, it may be something that's very rare, in which case we want to know," say Chris.

For those in York, there will be a special event in the Museum Gardens this Saturday and Sunday, where RSPB staff will be on hand to give advice on how to take part. There will be tick-sheets available for anyone who wants to go off and birdwatch by themselves, and garden guides to give tips on where to find different species. The sightings will be recorded on a board at ‘basecamp’ - but the event will also be great training for anyone who wants to do a birdwatch in their own garden. For more information visit yorkmuseumstrust.org.uk/whats-on/events/

PANEL

The ten most common wild birds in North Yorkshire spotted during last year's Big Garden Birdwatch (all illustrated on these pages) were:

- House sparrow

- Blackbird

- Starling

- Blue tit

- Wood pigeon

- Goldfinch

- Chaffinch

- Great tit

- Robin

-Long tailed tit

The RSPB's conservation scientist Daniel Hayhow says taking part in the Big Garden Birdwatch is a great way to help wild birds.

"The birds we see in our garden are often the first experience we have with nature – whether it’s a flock of starlings at the feeder, a robin perched on the fence or some house sparrows splashing in the bird bath," he says.

"But it may come as a surprise to know that some of our most-loved species are in desperate need of our help as their numbers have dropped dramatically. Species such as starlings and greenfinches have seen their numbers visiting gardens decline by 79 and 59 per cent retrospectively since the first Birdwatch in 1979.

“By counting the birds that visit your outdoor space, you’ll be joining a team of over half-a-million people across the UK who are making a difference for nature. It only takes an hour so grab a cuppa, sit back and see who makes a flying visit to your garden.”

As well as counting birds, the RSPB is once again asking participants to log some of the other wildlife they have seen throughout the year. This year, people are being asked to look out for badger, fox, grey squirrel, red squirrel, muntjac deer, roe deer, frog and toad.

To take part in the Big Garden Birdwatch 2018, participants should watch the birds in the garden or local park for one hour at some point over the three days. Only the birds that land in the garden or local park should be counted, not those flying over. The highest number of each type of bird seen at any one time then needs to be sent to the RSPB.

For a free Big Garden Birdwatch pack, which includes a bird identification chart, plus RSPB shop voucher and advice to help attract garden wildlife, text BIRD to 70030 or visit rspb.org.uk/birdwatch

A parallel event, the Big Schools’ Birdwatch, takes place during the first half of spring term. Further information can be found at rspb.org.uk/schoolswatch