This year's mild winter may mean some commonly-seen birds are proving a "bit elusive" in gardens, the RSPB said today as it launched its annual bird watch.
The confusing weather has seen temperatures swing between warm and freezing, with rain, high winds and snow thrown in, but the generally mild conditions have meant there is more food for birds in the countryside.
With their food not covered by frost and snow and with berries and insects available across the landscape, birds have not been visiting gardens to take advantage of the food put out for them on bird tables.
But people taking part in the Big Garden Birdwatch this weekend may notice that spring is starting early, with some birds already checking out potential nesting spots.
And heavy rain and strong winds could send some surprises into gardens, the RSPB said.
Half a million people are expected to take part in the Big Garden Birdwatch, spending one hour over this weekend, January 28-29, counting the birds in their garden or park and recording the highest number of each bird species seen at any one time.
RSPB Big Garden Birdwatch project manager Sarah Houghton said: "The last few months have been anything but predictable so it will be interesting to see what kinds of birds people are seeing this weekend and in what numbers.
"With plenty of natural food still about, some of the usual suspects might be a bit elusive, but heavy rain and strong winds could send other surprises our way.
"And spring-like signs might even be inspiring early breeding activities. There's already been lots of evidence of birds recce-ing potential nest sites so whatever the weather, it'll be a busy time."
She said birds which may start nesting early include blue tits, great tits and robins, and urged people to keep an eye on their nest boxes as well as bird feeders.
The Big Garden Birdwatch has been conducted every year since 1979, during which time sparrows, starlings and blackbirds have remained the most commonly spotted species - although numbers of all three have fallen.
Blue tits, wood pigeons and great tits are among the species whose numbers have increased in gardens in the past three decades.
The wildlife charity also said householders should be prepared with good quality food and clean, hygienic feeding stations in case of a late cold snap in February, which could be a shock for birds.