The old saying about “one swallow not making a summer” has long been used to leave a cautionary note over fine weather early in the year. With temperatures hitting a record-breaking 20.3C in the UK this week, still a whole month before the spring equinox, nature lovers have been treated to unprecedented arrivals of migrating birds returning extraordinarily early from Africa. Yet with swallows and house martins on the wing and sightings of scores of sulphur-coloured brimstone butterflies and bumblebees, naturalists are warning there still might be a sting in the tail for the nation’s wildlife.
Experts at the Royal Society for the Protection of Birds today warned the blue skies and balmy temperatures could end in a crisis for nature if it is led into a false sense of security by the current warm spell.
Already there are reports of robins and blackbirds building nests, laying eggs and raising chicks, but any sudden cold snap strike – the mini Beast from the East hit the UK as late as March 17 last year – could hatch dangerous times for garden birds and other creatures.
Charlotte Ambrose from the RSPB’s Wildlife Team explained: “Birds rely on environmental cues such as temperature to know when to start making a nest and start breeding.
“Because of the extremely mild weather, some birds and other wildlife are starting early. This is not necessarily a bad thing as it may allow some birds to have an extra brood before the main breeding season starts, but if the weather changes back to more normal conditions, the birds may get caught out and struggle to find enough food for themselves and their young.
“If invertebrates emerge early they will be here when the early nesting birds and their chicks need them, but again a cold snap could mean they don’t survive. Any sudden bad weather can kill-off early flowering plants, which are a source of nectar for insects, meaning they will struggle to find enough food.”
Already forecasters are predicting a significant change in the Mediterranean conditions most parts of the country have enjoyed for the past week. Rain and average seasonal temperatures of 10C are expected to return on Thursday and continue into the weekend.
Cooler conditions could be troublesome for the unprecedented numbers of swallows as well as house and sand martins that have been arriving from across tropical Africa over the past two weeks, courtesy of the “Saharan plume”.
Late March into April is usually the first time of the year when most people spot a swallow, but up to 30 have been counted across the country since February 10, reports the British Trust for Ornithology.
Similarly, since the first house martin was sighted in Cornwall on February 15, there have been 20 individuals recorded, including four birds that made it as far north as Shetland.
As crocuses, daffodils and fruit trees bloom, brimstone butterflies, bumblebees, hedgehogs and pipistrelle bats have been reported in gardens across the country.
For all nature’s spectacles blossoming during the warmest February since records began, the spectre of climatic change threatens long-term impacts for many species.
Martin Harper, the RSPB’s director of global conservation, warned: “While the warm weather, bright sunshine and abundant sights and sounds of nature undoubtedly make us all feel better, they should also ring alarm bells. The early signs of spring are likely down to climate change, which is bad news for us all. As we expect the weather to return to temperatures more traditionally associated with this time of year – as they are forecast to – then there could be a real crisis for our birds, insects and other wildlife.”