Nature is so confused by the mild winter conditions that many species of animal and plant are convinced that spring has arrived.

Birds have started nesting, bumblebees are finding a supply of snowdrops and daffodils, and tadpoles have been spotted in ponds.

The cold snap last week curbed enthusiasm briefly, but Britain’s wildlife has now resumed the dash towards the serious business of finding food and starting a family.

Volunteers for the Woodland Trust have reported hundreds of sightings of animals and plants that are behaving as if spring were here. The early start for many species is in line with the trend over the past decade and is attributed to the effects of global warming.

Observations reported to the Nature’s Calendar survey, run by the trust, include hazel catkins appearing as early as December 9, snowdrops in flower on December 10 and 47 sightings of seven-spotted ladybirds last month.

Butterflies making unseasonable appearances include a red admiral on January 6, four months before it would be expected, and a peacock butterfly on December 31, two-and-a-half months early.

Collared doves and rooks are among the birds most confused by the mild weather, which has tempted scores of pairs to start nesting. Robins and bluetits have also been caught out.

Spring behaviour tends to be seen first in southern Britain, but the effects are just as much in evidence in the North, with catkins out in Lancashire and snowdrops in Yorkshire in the middle of last month.

“There are a lot of early sightings, such as active ladybirds and butterflies out and about,” Kate Lewthwaite, of the Woodland Trust, said.

“The natural world is giving us clear year-on-year indications that things are changing. The timing of natural events is one of the most responsive aspects of the natural world to warming.”

She was most surprised by sightings of tadpoles in Devon and London, but frogspawn have been seen as early as December, and newts were seen last month.

Reports from the survey will be analysed to assess how much earlier this year’s spring events are compared with the average. It is thought unlikely that this year will match last year, when the mildest spring on record meant that the season started 23 days earlier than average.

Temperatures for last month were 5.3C (9.5F), cooler than the 6C of last year, but well above the long-term average of 3.4C and the eighth-warmest on record.

Britain’s climate is expected to become warmer and wetter during winter, encouraging many species to emerge early, but cold snaps, which can be devastating for early starters, are still going to be a feature. Frogs breed only once a year, so if frogspawn were killed by the cold, a generation would be lost. Similarly, butterflies that appear too early usually die if frosts return.

Woods and forests are likely to change if the trend for warmer winters continues. Oaks would be expected to thrive because they can exploit the milder weather by sprouting buds earlier, whereas ashes struggle to keep up.

Dr Lewthwaite said that while some people judge the arrival of spring by the equinox, and others by the calendar, many will decide it has started when they see a favourite plant or animal. For many birdwatchers it is likely to be the arrival of migrant birds, particularly the chiffchaff. Traditionalists will stick to the first cuckoo.

For Dr Lewthwaite it was the sight of snowdrops in the Midlands. “It’s sunny and the snowdrops are out. Spring has sprung for me.”

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