People taking part in the Big Garden Birdwatch – the biggest wildlife survey in the world – may see the tiny garden visitors, organisers the Royal Society for the Protection of Birds (RSPB) said.
Species such as wrens and long-tailed tits suffer during long, cold winters, but the milder January weather may have proved a boon to them this year.
The charity has also had reports of early nesting activity in some species, which is likely to be linked to the higher temperatures.
But warmer weather can also mean fewer birds seek out food and shelter in gardens as conditions are good in the countryside, so wildlife watchers may spot fewer of their usual garden visitors in the survey.
The Big Garden Birdwatch has been running for the past 41 years.
Almost 140 million birds have been counted over that time, helping conservationists identify dramatic declines and increases in garden birds, the RSPB said.
For example, it was one of the first surveys to alert the conservation group to the declines in numbers of song thrushes, with populations of the bird having fallen by 76 per cent over the four decades of the survey.
To take part, people just need to watch the birds in the garden or local park for one hour over the three days of the survey, taking place from today. Participants are asked to record the highest number of each species they see at any one time. With the exception of red kites, which people can record if they see them flying over, only birds that land in the garden or park should be counted.
Beccy Speight, the RSPB’s chief executive, said: “The data gathered by Big Garden Birdwatchers over the last 40 years has helped chart the decline and rise of numerous species since the 1970s.
“And contributing to that important piece of citizen science is for many thousands of people a first step in becoming champions for nature.
“More than ever we need everyone to be interested in the wildlife immediately around them. It’s endlessly fascinating.
“And at the RSPB, we’re confident that the more time we all spend in nature, the more we will be passionate about protecting and restoring it.”
Close to half a million people are expected to take part in the Big Garden Birdwatch and the RSPB is asking households to share their stories of how they take part.