Flight of the winter bumblebees

ANOTHER LIFE:The National Gallery diary for 1988, a cheering, floral affair with hollyhocks on the cover, has been my Diary of Things Seen, grabbed to make a note in before I forget. It was begun in the era when nature still followed some consistent order of seasons, so that recordings of early primroses, celandines, first bumblebees, and frogs mating in the pond were felt to have some significance. Now, with “the end of nature”, as Bill McKibben famously put it, anything goes.

But sometimes I still want to share. January 13th this year was “Another mild, wet morning. A song thrush singing atop the hawthorn outside my window. I opened it (double glazing) to listen.” For a couple of mornings, indeed, the same thrush was unstoppable, pouring out a full territorial cantata. That, of course, was before the snow.

Wildlife has always had to cope with winter’s erratic progress, but there used to be a few steady certainties. One was that the summer colonies of worker bumblebees and wasps always died off in winter, leaving just a newly mated, hibernating queen to start things again in spring.

But Frank Smyth, a reader, took a walk on the cliffs of Howth on January 4th, a calm sunny day, and saw not only two red admiral butterflies, already known to overwinter on that headland, but half a dozen buff-tailed bumblebees and two wasps, all workers gathering pollen from late-flowering ivy and hebe. Reporting this to Eye on Nature, he was handed the standard dogma that only bumblebee queens survived the winter. This, it now seems, was almost certainly mistaken. Bombus terrestris, the buff-tailed bumblebee, has started doing things differently.

Mr Smyth’s observation was promptly supported by Bob Aldwell, past president of the Dublin Naturalists’ Field Club and notable student of butterflies and other insects.

“Here in Dublin,” he informed me, “over the past 10 years or more, it has been usual to observe B terrestris workers as well as queens foraging on a range of winter flowering plants and shrubs throughout the winter months. These include hebe, arbutus, mahonia, gorse, cyclamen, various heathers, etc. As a former beekeeper I can only conclude that the heavily-laden pollen workers indicate an active colony with young brood requiring the pollen as protein.”

He had seen winter bumblebees regularly in Howth, Sutton, Blackrock, Dalkey and Killiney, all coastal areas with “positive microclimates”. Here, “on sunny winter days, up to a dozen bumblebees may be seen working away on flowers such as cyclamen”, their furry coats keeping them flying in temperatures only a little above zero. Even a bit further inland, winter Bombus have been seen in Rathfarnham and the National Botanic Gardens, in Glasnevin.

Winter foraging

The winter foraging of bumblebees is already under study in southern England. Experimental colonies of B terrestris, with individually wireless-tagged bees, were set up in autumn in London. Here, the massed lemon-yellow flowers of mahonia, common in parks and gardens, helped the winter bees to reach foraging rates even better than those of the summer.

Dublin, too, is something of a heat island compared with the open countryside. But here, as in England, the flight of winter bumblebees is complicated by identity: is this the real native Bombus nuzzling the garden centre blossoms or an alien impostor?