As the RSPB, bird-watchers and gardeners nationwide gear up for the charity's annual Big Garden Birdwatch, the organisation is warning that birds that have benefited from a mild autumn will begin to struggle as the weather changes.

Results from the findings of the 2014 event, in which almost half a million people recorded the birds they saw over the two days, revealed some interesting changes among our most popular garden birds, with some species that benefit from a bit of extra help creeping up the rankings.

Blue tits emerged in their highest position since Big Garden Birdwatch began, at number two. The previous occupiers of the second spot, blackbirds, dropped to number four. Goldfinches climbed another place since the previous year and reached number seven while the robin dropped back to number 10. There was a new entrant to the top 20 - for the first time ever the great spotted woodpecker squeezed in at number 20.

As well as asking the public to record their findings - with the help of identification pictures available on the RSPB website www.rspb.org.uk - the organisation is also asking people to do their bit to protect our birds through the winter by topping up their bird feeders and providing fresh water and shelter for wildlife in their gardens during the frosty weather.

The nature charity says there are three key things that birds will need this winter: food, unfrozen water and shelter.

1. In chilly weather, birds will appreciate a variety of food, but fatty food will be especially helpful. For example, fat balls, or homemade bird cakes made with lard and packed with seeds, fruit or dried mealworms are great treats to put out in your garden. Kitchen scraps will work well, and a recipe for successfully feeding birds over winter might include chopped fat from unsalted meat, cheese, dried fruit and pastry.

2. Unfrozen water for drinking and bathing may be hard for birds to find when there's been a frost, but with a simple trick you can help to keep a patch of water ice-free. Float a small ball, such as a ping-pong ball, on the surface of the water. Even the lightest breeze will keep it moving and stop an area of the water freezing.

3. Provide shelter by planting dense hedges such as privet or hawthorn, or allowing ivy or holly to grow. These all provide great cover for birds to roost in. Nestboxes can also be good roosting sites. Roofs are also a popular spot for birds trying to keep warm. If birds are getting into a hole in your roof and you need to get the hole fixed, consider putting up a nestbox to replace the gap. Find out more about giving nature a home in your garden here: rspb.org.uk/homes

RSPB wildlife advisor Richard James says: "People can make a real difference to garden birds and improve their chances of surviving the winter.

"Birds don't need much and by providing a supply of food, a patch of unfrozen water and somewhere to shelter from the elements, you will be rewarded with great views of wildlife in your back garden.

"While birds need fatty foods, you shouldn't put out fat from a roasting tin, such as turkey fat from Christmas, as this runny fat can coat birds' feathers, making it difficult for them to move or fly."

The RSPB's annual Big Garden Birdwatch, the world's biggest wildlife survey, returns on Saturday and Sunday, January 24 and 25. To take part, people are asked to spend just one hour at any time over that weekend noting the highest number of each bird species seen in their gardens or local park at any one time. They then have three weeks to submit their results to the RSPB, either online at www.rspb.org.uk/birdwatch or in the post.

Last year's event revealed that house sparrows were the most recorded birds despite their falling numbers. The full results can be viewed online at rspb.org.uk/birdwatch