Of all the bumblebees in Scotland – and at the last count there were around 22 species – the Great Yellow is the one that gives greatest cause for concern. One hundred years ago the Great Yellow Bumblebee was found in many places across Britain, today it is confined to Scotland. Even then it is only found in parts of the Western Isles, Orkney, Coll & Tiree, and lowland Caithness, with a very small presence on the coastal fringes of Sutherland.
The decline of the Great Yellow is not a new story. Its decline has been noted since the 1960s and appears to coincide with changes in land use and fewer of the flowers it depends on being present. There is a clear correlation between its presence today and low intensity crofting, and that type of farming is intimately associated with knapweeds, clovers and vetches. It is the kind of habitat and farming practice we associate with machair.
The bees love the flower-rich machair grasslands in the Western Isles, which in turn benefit from the traditional farming practices for survival. By limiting grazing and avoiding cutting flowers in summer the agricultural practices of the areas undoubtedly help the Great Yellow Bumblebee.
As part of Scotland’s commitment to protecting biodiversity, machair habitat is eligible for special agricultural funding. The great yellow bumblebee was indeed one of the species which received additional attention through the Species Action Framework.
Our largest bumblebee, the plight of the Great Yellow struck a chord in Caithness where the northerly region took the insect to its heart. This was clear when the town of Thurso championed the Great Yellow and by a mixture of education, and wide-ranging practical actions set about creating and managing habitats that would help it survive.
The most southerly populations of Great Yellow that we are aware of in Scotland are found in Coll and Tiree. Coll can be a wildflower haven in summer and is home to some fabulous species. Birds in particular draw visitors like a magnet. The secretive corncrake, noisy lapwings and powerful sea eagle can all be spotted in this area. On Tiree, the Community Development Trust, together with RSPB, crofters and local volunteers have been working hard to create a haven for ‘the great yellow’. This has taken many forms with recording sightings and issuing wild flower seed packs amongst the successful approaches.
There was good news recently with a funding bid for Tiree’s great yellow bumblebee project being awarded £2,000 from Tesco Bags of Help fund. The money will support the community to monitor and record this very rare bumblebee and to increase and improve habitat to help ensure the survival of Great Yellow Bumblebees on Tiree. Indeed the project was shortlisted for the prestigious Nature of Scotland Awards 2018.
It isn’t usually until mid to late-May that the queen Great Yellow emerges from hibernation, in a cool summer it may even be June. This arrival will likely coincide with the availability of bird’s-foot trefoil, vetches and thistles. She will stock up on reserves then move to an underground nest fairly soon afterwards (this is often an abandoned mammal nesting hole, which in some cases may have nesting material already in situ) but even at the peak her nest will likely only contain tens of workers.
These workers are likely to be on the wing from mid-July onwards and their likely food supply will feature knapweed and red clover. At the end of the season, around September, the old queen and the workers die with the new young queens heading off to hibernate underground.
A spectacular bee, it is entirely yellow except for a black band on the top of the thorax between the wing bases and black patches below the wing bases. Queens are large and have a fairly distinctive long face rather like a carder bee.
So what can be done to halt the decline in numbers of the Great Yellow Bumblebee in Scotland? Habitat is crucial, which points to maintaining the distinctive flower-rich machair habitat. This will give food, nesting and wintering sites. A visit to the Balranald Nature Reserve run by the RSPB offers an insight into this low intensity form of farming which is sympathetic to the survival of machair pasture. Allied to this, it is likely that the area will continue with low pesticide usage and the avoidance of exposure to managed bees or the large-scale introduction of honey bees.