Super bees are buzzing through the winter chill
Climate change leads insects to give hibernation a miss
Colonies of super bees are surviving Irish winters, according to the National Biodiversity Data Centre.
Scientists there say workers and queens of bumblebees are living through our coldest months.
"More than usual have been reported this winter, mainly in the east," said Dr Una Fitzpatrick, ecologist at the National Biodiversity Data Centre. She believes climate change is primarily responsible.
The phenomenon had been noted in urban areas, but this year has seen more sightings too from rural gardens. Usually bumblebee queens hibernate through the winter months, with the earliest flying out again in February or March.
"Queens of any species can accidentally come out of hibernation too soon in a mild winter spell, but this is different. It's deliberate overwintering of one particular species," said Dr Fitzpatrick.
"Queens could be fooled into coming out of hibernation on warm days. But if you are seeing workers that means there is a bumblebee colony," said Dr Jane Stout, bee ecologist in Trinity College Dublin.
Ireland has 20 types of bumblebee, but it is only the white-tailed bumblebee species surviving through the winter. The overwintering super bee is the largest bumblebee species in Ireland and one of our most important pollinators of wild flowers and crops.
"This has been happening more and more over the last decade, especially in urban areas where there are more food sources for the bees," Dr Fitzpatrick said.
Instead of two bumblebee broods a year, the overwintering colonies may be running up more, Dr Stout added. This could give them a competitive edge in spring.
Workers from the winter colonies have been seen feeding on mahonia, hebe and cyclamen flowers, all non-native plants now commonly grown in Irish gardens. It could equally be a worry if the overwintering colonies are dying out during cold spells.
"This is an incredibly important pollinator and we need to have robust colonies in spring and summer," she said.
Another possible explanation is that soft fruit growers have been importing boxes of bumblebees to pollinate crops. These foreign white-tailed bumblebees could be escaping. "One subspecies being imported naturally overwinters in the Mediterranean area," said Dr Fitzpatrick. The foreigner could in theory breed with our own native bumblebee.
The National Biodiversity Data Centre said it was grateful to those who submit bee sightings at www.biodiversityireland.ie. There has been concern over bee declines in Ireland in recent years. Scientists have blamed habitat loss, loss of wild flowers, diseases and agrochemicals. Climate change could make matters worse, but its full impact on Irish bees remains to be seen.
Unlike honeybees, bumblebees don't make large quantities of honey. "Bumblebees are always only a couple of days away from starvation," said Dr Fitzpatrick. They live in small nests and store small amounts of nectar. They can die if cold or stormy weather keeps them inside for too long.