Buff-tailed bumblebee Bombus terrestris on Gorse Image: Kevin Thomas, Falmouth Nature |
As Kevin says, "NYPH has shown that in milder winters, more plants flower because of warmer temperatures and fewer frosts. We don't yet know what the implications of this are for plants and associated insects - but what we do know is that weather patterns are changing and that plants are responding".
Bombus terrestris on a range of plants Photographed on 30th January 2019 Image: Charlotte Rankin |
Of course, before we can get to grips with the possible impacts of changing weather patterns on our plants and insects, we need to know what is "usual" at this time of year. So, to help those of us (like me!) whose botany is much stronger than our entomology, I asked conservationist and insect ecologist Charlotte Rankin to talk us through which pollinators are usually on the wing at this time of year and which plants they are most likely to visit - native species? Naturalised garden plants? Or perhaps the winter-flowering shrubs we see in parks and gardens which rarely naturalise?
Charlotte has a first class degree in Conservation Biology and Ecology, and a strong track record in community engagement and public outreach. She is also a botanist and took part in this year's North-East New Year Plant Hunt-Off in Northumbria, so she is ideally placed to bridge the gap between flowers and pollinators!
Bombus terrestris heads for a Rosemary plant Image: Charlotte Rankin |
Over to Charlotte:
"For most flowering plants and their visiting insects, Winter
is a time for rest and preparation for the warmer seasons ahead in the UK.
However, there are some quiet buzzes in the urban air and, as shown by this
year’s New Year Plant Hunt results, over 600 species of wild or naturalised
flowering plants can be found in bloom. Honeybees and various species of fly can
be active on particularly mild winter days and most notably, brave and bold Bombus
terrestris (Buff-tailed Bumblebee) queens can establish winter-active colonies.
"What forage can urban areas offer for such pollinators in Winter?
At a glance, results from the New Year Plant Hunt provides insight into what
wild or naturalised plant species may well be available for urban pollinators
out in Winter. The top 20 plants found in flower during this year’s Hunt shows
that there are species particularly attractive to pollinators, such as the
trusty Taraxacum spp. (Dandelion), Achillea millefolium (Yarrow), Sonchus
oleraceus (Smooth Sow-thistle), Hedera helix (Ivy) and Jacobaea vulgaris (Common
Ragwort), that can hang onto Winter.
Bombus terrestris on Winter Heliotrope Image: Charlotte Rankin |
"Urban areas also tend to have more
naturalised non-natives that could be exploited, including Centranthus ruber
(Red Valerian) and Petasites pyrenaicus (Winter Heliotrope). However, private
gardens, parks and other amenity areas also introduce a variety of exotic winter-flowering
plants, that by flowering at their peak during these months, can offer a rich
resource of nectar and pollen throughout the Winter.
"Winter-active nests of Bombus terrestris are associated with
Southern, urban areas of England and were first noted in the 1990’s. Rather than
hibernating, some queens produced in late Summer/Autumn may establish a nest
and maintain it throughout the Winter months.
"In order to do this, nests need a
continuity of nectar and pollen and it seems that colonies deal with the depths
of Winter by utilising exotic winter-flowering plants, particularly mass-flowering
shrubs.
Bombus terrestris on Winter Honeysuckle, Mahonia and Winter Heather Image: Mike Robinson |
"There has been some published research on the winter
foraging activity of Bombus terrestris: A study by Stelzer et al. (2010)
showed that commercial Bombus terrestris colonies in London relied upon
mass-flowering garden shrubs such as Mahonia and could achieve foraging rates
like that in Summer. An ask on Twitter
also showcased the exotic tastes of Bombus terrestris, with the large majority
of sightings on a great range of garden plants including Mahonia spp., Lonicera
fragrantissima (Winter Honeysuckle), Hebe spp., Camellia spp. such as ‘Cornish
Snow’, Winter-flowering Erica spp., Jasminum nudiflorum (Winter Jasmine) and Helleborus
spp. (Garden Hellebores).
"These plants all share something in common: they flower at
their peak during Winter, providing these bumblebees with an abundance of
nectar and pollen to develop their colonies. As a generalist species active during
these tricky months, it makes sense for these bumblebees to focus their
foraging on these mass-flowering plants. While wildflower species attractive to
bumblebees could well be present, their flowers are few and far between compared
to their prime months of flowering to be relied upon.
Episyrphus balteatus on Gorse Image: Kevin Thomas, Falmouth Nature |
"Winter workers can be seen using the native Ulex europaeus (Gorse), appearing to collect its pollen. Some workers may even venture into
allotments and make
use of broccoli that has been left to flower and have been spotted using
the invasive
and naturalised Winter Heliotrope.
"On mild Winter days, there are three species of hoverfly likely
to be seen: Meliscaeva auricollis, Eristalis tenax and Episyrphus balteatus.
Winter hoverfly sightings from Twitter and the UK Hoverflies Facebook Group
provide insight into what plants they visit, including visits to wildflowers
such as Taraxacum agg. (Dandelion), Ulex europaeus (Gorse) and
early-flowering Ficaria verna (Lesser Celandine).
Meliscaeva auricollis on Viburnum Image: Will George |
"Again, exotic plants appear
to be a valuable forage resource, with sightings on species such as Mahonia, Viburnum
tinus (Viburnum), Lonicera fragrantissima (Winter Honeysuckle), Erysimum spp.
(Perennial Wallflower) and Jasminum nudiflorum (Winter Jasmine).
"In the depths of winter, exotic mass-flowering plants can provide
a reliable and rich resource of nectar and pollen. Winter-active nests of
Bombus terrestris appear to have a strong association with these plants and
currently, wildflowers found straggling on into Winter likely do not provide
sufficient forage to be utilised alone.
Eristalis tenax on Dandelion Image courtesy of Trevor Kerridge |
"Towards the end of Winter and early
Spring, a variety of early-flowering species such as Lesser Celandines and Blackthorn begin to flower, and their importance as magnets for early-emerging
pollinators should certainly not be overlooked. More data is needed on the
winter foraging activity of bumblebees and other pollinators that may venture
out on mild winter days. Sightings of winter-active bumblebees can be submitted
online to the Bees, Wasps
and Ants Recording Society (BWARS)’s winter bumblebee project."
Many thanks to Charlotte for these helpful insights into a pollinator's eye view of our winter flowers, whether wild or in gardens. Thanks also for the superb images she sourced to illustrate this post: some are her own and some were sourced from her network of contacts. Many thanks to them too and we have shared links to their Twitter accounts so you can follow them. You can also follow Charlotte on Twitter for more of her observations on the natural world and our wonderful wildlife, both plants and animals.