By Emma Brennand
Earth News reporter
The goldfinch brings a splash of colour to our gardens
One of the world's largest wildlife surveys, "the big garden birdwatch" is being launched by the UK's Royal Society for the Protection of Birds.
The charity hopes that around half a million people will record the abundance of different bird species visiting their gardens and open spaces.
By asking members of the public to spend one hour this weekend spotting birds, the charity can identify those species in most need of help.
The survey is now in its 32nd year.
This year it starts on Saturday 29 January.
The results will be particularly useful in helping conservationists understand how the coldest December since records began has affected garden bird numbers.
"The really cold weather began quite early in December, and this would have been when natural food sources became scarce," said Dr Mark Avery, the RSPB's director of conservation.
"By now, these birds could have been making the most of our hospitality for over a month, meaning even more unusual sightings this weekend."
In addition to our usual garden visitors such as blackbirds, blue tits and robins, the charity expects some unusual sightings in the survey, with increasing visits by less common birds such as waxwings.
Dr Avery said: "Regardless of where they live, or the size of their outside space, people in the UK have been united this winter in their wish to try and help garden birds."
You do not need to have a garden to take part. Participants are expected to join in from a wider variety of gardens and public open spaces, including parks.
The RSPB is asking people to download a form from its website and use it to record the highest number of every bird species seen at any one time.
This data is then collated across the country to give an overall indication of how populations of different species are faring.
Richard Benyon, Minister for the Natural Environment, says: "The big garden birdwatch is something everyone can get involved in and I'm looking forward to taking part this year."
He adds:"Our bird populations are a good indicator of the wider health of our environment and the valuable information collected will help us understand more about why birds are in decline and what we can do to help them."
Over the past 30 years, the survey has helped reveal insights into the nation's changing bird populations.
For example, the survey helped reveal that house sparrow numbers in gardens have fallen by 62% between 1979 and 2010.
Similarly, starling populations have plummeted by 79% since 1979.
However, blue and great tits have endured, making regular appearances each year in the top 15 most abundant species.
Last year, more than half a million participants helped record over 8.5 million birds covering 73 species across nearly 280,000 gardens.