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?

In February 2009, Bob Aldwell was intrigued to watch “a form of Bombus terrestris” (he’s a cautious man) emerging from a hole on the sunny side of a bank in Dalkey. “During five minutes, 10 bees exited the hole and eight entered. All these returning workers were laden with red pollen.”

Clearly, an active colony – but might they be, he had to wonder, the new and near-identical alien intruder, a subspecies of B terrestris originating in the Balkans, Greece and Turkey? Imported commercially by Ireland’s strawberry and tomato growers to pollinate the plants in their polytunnels and greenhouses, Bombus terrestris dalmatinus breeds two generations a year, where the Irish and British island subspecies have historically settled for one.

Just a decade ago, I noted some 800 colonies of this Mediterranean bee being flown to Dublin in a year by a British supplier. If new queens hatched in the tunnels, ecologists were asking, could they live to escape and breed outside captivity, perhaps hybridising with our native subspecies and disrupting their patterns of pollination? Dr Tom Ings of Ruskin Anglia University, who leads British research on the question, finds the escaped aliens “ecologically superior” to the UK’s native B terrestris – better nectar foragers and better breeders. This may not be entirely good news.

As for the wasps, a reader in Stillorgan, in south Co Dublin, found a large nest at the end of his garden still quite active on December 9th. The UK's Bees, Wasps and Ants Recording Society has launched a project to record winter-flying B terrestris in both islands (at bwars.com). There will be more to come, no doubt, about the wasps.

Eye on Nature Your notes and queries

When I was out for a walk two foxes ran across the field ahead of me and disappeared into the hedge. They started making a sound like “tru-iip-tru-iip-tru-iip” repeatedly. They carried on for some minutes.

Yanny Petters Enniskerry, Co Wicklow

David Macdonald, in his book Running with the Fox, terms that sound “gekkering” . It is made by a dog fox seeing off a rival in the courting season, or by a vixen rebutting a too-forward suitor.

While out walking by the Boyne on New Year’s Eve, just below Bective, we found a three-foot salmon on the bank that weighed 17lb. It was a cock fish in very good condition, only slightly red, and not long dead, as rigor mortis had not set in. His throat had been eaten, probably by an otter.

Bonnie, Harry and Rubie MacCann Bective, Co Meath

Good to report plenty of redwings and fieldfares on this side of the country, and blue, bearded and long-tailed tits at my feeders.

Tom Curtis Fitzwilliam Quay, Dublin

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo, or email viney@anu.ie. Please include a postal address