Bishop's Stortford residents can take part in the RSPB Big Garden Birdwatch 2020

This weekend (January 25-27), we'll be spending an hour watching the birds in our garden.

My kids are very excited to be taking part in the RSPB's Big Garden Birdwatch, the world's largest wildlife survey. All you have to do is to watch the birds for an hour and submit your results to the RSPB by February 16. More than half a million people are signed up to take part.

The survey has been going for over 40 years. It's very difficult to observe changes in bird populations as they happen very slowly, but more than 40 years of comparable data makes it possible to monitor trends and understand how birds are doing. The survey reveals a 76% decline in song thrushes in our gardens between 1979 and 2019, and a 60% decline in house sparrows since the mid-1970s, particularly in large city centres.

In fact, according to the RSPB, there has been a "serious countrywide decline" in the numbers of many farmland birds, largely as a result of changes in agricultural practices that have impacted access to food, habitats and nesting places. Cuckoos have declined by 33% since 1970, skylarks by 71% and tree sparrows by 95%.

However it's not all bad news. Most woodland birds, such as the blue tit, nuthatch and greater spotted woodpecker, are holding their own and populations of some garden birds are on the increase, thanks to the British love of bird feeding. We spend £200-300 million on bird feeding each year and it is having a measurable impact on the number and variety of birds in our gardens, stimulating population growth across more than 30 different bird species.

Birds are also feeling the effects of climate change. Here again, the picture is mixed. For most, the impact so far has been positive, as warmer temperatures improve survival rates over the winter. There's certainly an abundance of blackbirds, robins and blue tits in full voice in my garden. However, it's not good news for all. Cuckoos, little owls and reed warblers have seen their numbers fall by at least 10% as a result of climate change.

Climate change is changing the types of birds we see. Some birds are moving north, in search of cooler weather whilst new species, including quail, little egret and hobby, are colonising southern Britain as continental Europe becomes too hot and dry. More birds are over-wintering in the UK rather than migrating to southern Europe and those that do migrate are staying here for longer. Swallows for example are here up to four weeks longer than in the 1960s.

Birds are one important indicator of the overall state of UK wildlife. The 2019 State of Nature report, produced by over 70 wildlife organizations and government conservation agencies, found that populations of the UK's more important wildlife, including hare, hedgehogs, bats and turtle doves, have plummeted by an average of 60% since 1970. The study concluded that a quarter of UK mammals and nearly half of the birds assessed are at risk of extinction. Kate Jennings, head of site conservation policy at the RSPB, had this to say in response: "Nature in the UK is pretty bad, declining and not recovering and that is in the context of an awful lot of rhetoric [from ministers] about being a world leader on environment."

Happily there are now more positive signs coming from government. You may have seen news last week of the publication of the new Agriculture Bill, setting out what will happen to farm subsidies after we leave the EU. In the future, farmers will be rewarded for providing services to society such as clean air, clean and plentiful water, flood protection and thriving wildlife. This is a radical shift in the way we manage our land. When you remember that 80% of the UK is in fact farmland, you begin to realise just how widespread the impact of this bill could be.

The changes, which will be phased in over seven years, have been broadly welcomed by wildlife and conservation groups. Tom Lancaster, head of land use policy at the RSPB, said: "The Agriculture Bill is a crucial step in the fight against the climate and environment emergencies, and as it stands will enable farmers and land managers in England to lead the way."

So there's reason to be hopeful about the future of birds and wildlife in the UK. In the meantime, you can look after the birds in your garden by putting out food and fresh water, for drinking and bathing. Check out the RSPB website for detailed advice on what to feed and when.

And it's not too late to register for the Big Garden Birdwatch this weekend. Sign up at www.rspb.org.uk and get out your binoculars.