The hunt for rare bumblebees at RSPB Dungeness; a lab trip

 

A windswept headland that lies in the shadow of a nuclear reactor might not seem like the most obvious place to go searching for rare bumblebee species, but that’s exactly where the Brown lab headed on a lovely spring day early in May. To be more precise, we were heading to Dungeness in Kent, where you can find one of the largest expanses of shingle in Europe. The shingle creates a desolate landscape, but this area actually harbours high levels of biodiversity. It is home to 600 plant species (a third of all UK species!), rare spider and insect species, and is also a good place to spot migratory birds. However, it was the insects, and more specifically the bumblebees, that we came looking for.

 

The area has a very high diversity of bumblebees and it is also one of the most reliable places to see hard-to-find species such as the moss carder bee (Bombus muscorum), the brown-banded carder bee (Bombus humilis) and the ruderal bumblebee (Bombus ruderatus). It was near Dungeness in 1988, where the short-haired bumblebee (Bombus subterraneus) was last reported in the UK. This species has now become the focus of a reintroduction campaign managed by the Bumblebee Conservation Trust, and every spring, queen short-haired bumblebees are released at Dungeness with the hope that they will establish colonies.

 

With all this in mind, we hit the road early on a Wednesday morning, with a car boot full of nets, and the skies looking promising…

 

Bumblebees are often associated with gentle summer days, flowers in full bloom and a delicate buzz in the air as they go about their seemingly endless work. During the summer, bumblebee colonies are in full swing, and the flowers they forage on provide nectar and pollen to sustain and help the colony grow. However, bumblebee colonies begin under more modest circumstances. Each colony is initiated in the spring by a single queen who has overwintered underground. The queens are much larger than workers, and when they emerge from hibernation they require energy from nectar to power their flight to forage, but also to locate potential nesting sites and raise their first brood.

 

Some of the UK’s rarer species of bumblebee, such as the moss carder bee, have longer tongues and as such these bumblebees require flowers with deep flower tubes. However, during the spring in temperate zones there can be an obvious lack in both floral diversity and abundance. Flowers with deep flower tubes, such as white dead-nettle (Lamium album) and ground ivy (Glechoma hederacea) grow in patches and can be seen as weeds by humans, but these flowers can provide valuable forage for newly emerged bumblebee queens. Thankfully, charities and groups such as the Bumblebee Conservation Trust are recognising the importance of spring foraging resources and are trying to manage landscapes in a way to increase floral diversity to help support bumblebee queens on their road to monarchy .

 

Many of the hotspots for sighting bumblebee queens on our trip were in fact along roadside verges where

 dead nettle and ground ivy thrive. These verges, if managed appropriately, can support high floral diversity and be important refuges in an agricultural landscape. In the UK, there are over 390,000 km of roads, that’s a lot of potential habitat for preserving our wild plants and pollinators! However, these verges also have a dark side – in a recent bioblitz by the Bumblebee Conservation Trust alongside a busy A road over 30%  of the bees recorded were road kill. Very few studies investigate the impact of roads on invertebrates and of those even fewer look at bumblebees. However, from studies of other invertebrates, it seems that the amount of traffic on the road is one of the biggest determinants of the amount of roadkill; the more cars, the more roadkill.

 

This is partly the reason that the Bumblebee Conservation Trust is trying to find other refuges of spring forage for the bumblebee queens and other insects around the RSPB Dungeness reserve. By having safer foraging patches and especially by simply having more spring forage, it is hoped that the important populations of rare bumblebee species on the reserve can be supported further in face of global pollinator declines.

 

Nevertheless, roadside verges and hedgerows will still play a vital role in providing forage for our wild bees, particularly in the spring. This could not have been more clear as we walked down a quiet countryside lane, dubbed ‘ruderal lane’ by our guide Dr Nikki Gammans. Here the lane was tightly bordered by fields of wheat and oilseed rape, with just a metre or so of verge on each side of the lane, but it was in this patch, among many other bumblebee species, that we made our only sighting of the prized ruderal queen bumblebee amongst the white dead nettles  (a great spot by newly appointed Lucy Witter at the Bumblebee Conservation Trust).

 

All in all we had a very productive day, with many of us making our first sighting of some of the UK’s rarest bumblebees; the moss carder bee and ruderal bumblebee, along with the more common but still beautiful red-tailed cuckoo bee B. rupestris, who lays her eggs in red-tailed (B. lapidarius) bumblebee nests instead of making her own. A particular high point came from a last minute spot of the brown-banded carder bee as we stopped to check one last patch of forage before going home. There were plenty of solitary bees and other insects to keep us entertained, too. Dungeness hosts the only known nesting aggregation in the UK of the grey-backed Mining-bee (Andrena vaga) and there were many nomad (Nomada) bees waiting to parasitize nests of other solitary bees. We may have been slightly more excited about all the bee species we saw, but there were plenty of other interesting insects for the budding entomologist to see; bee-flies (obviously our second favourites following the true bees), damselflies, hoverflies, butterflies, true flies and shieldbugs to name just a few (all recorded on iRecord where possible)!

 

 

Photos by: Mark Brown, Emily Bailes, Dylan Hodgkiss and Lucy Witter.

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