The great yellow bumblebee is Scotland’s rarest bee. Once widespread in the UK its distribution has declined by 80% in the last century, which is believed to be linked to the intensification of farming. As farming practices moved away from low intensity crofting, flower rich meadows reduced in number. The tussocky overgrown areas which great yellow bumblebees favour for their nests also reduced as more land was improved. Great yellow bumblebees are now usually found in areas where crofting practices have continued, such as the Inner and Outer Hebrides, parts of Caithness and Sutherland and Orkney. 

Croft, Scotland - Andy Hay

We’ve been working hard to increase numbers of great yellow bumblebee across our reserves and understanding the lifecycle is essential to this work. Great yellow bumblebee queens emerge from hibernation in late May to late June. Once they have fed and found a suitable nest site they will then lay eggs, which develop in to workers who provision the nest from then on. These emerge in July. The queen will then lay more eggs, these are males and queens. Males emerge in August followed by the new queens mid to late August. The timings of the lifecycle can vary substantially depending on the weather. The new queens will mate with the males and then find somewhere to hibernate, only these queens will survive the winter.

 

Great yellow bumblebee queen and male mating – Christine Hall

To provide for great yellow bumblebees we need to ensure they have a source of food (nectar) throughout the whole lifecycle, from May – September. Great yellow bumblebees use their long tongues to feed on the nectar of plants like knapweed, clover and vetch. In Orkney we have been managing several areas of our reserves as species-rich grassland. To do this we strip the fields of nutrients by cutting and removing vegetation each year in late summer or early autumn. Nutrient stripping is important as it reduces the competition from grasses, thistles and nettles which prefer high nutrient soils. The cuttings from the sites can also be used as green hay. This is where we cut an area which has high flower abundance and transport some of the cuttings to a field with lower abundance. The cuttings will then drop seeds in this area, potentially increasing the flower abundance the following year. Whenever we cut the fields we leave a margin at the field edge, this allows this vegetation to provide potential nesting and hibernating habitat for the great yellow bumblebee queens.

 

Cutting at Brodgar – Tim Lill

2018 is the fourth year of great yellow bumblebee surveys on RSPB Scotland reserves in Orkney. The surveys involve walking several lines through fields where we are managing for great yellow bumblebees. The trickiest part, at least in Orkney, is getting a day when the weather is nice enough for you to survey. It needs to be bright and warm (over 12oC) with little wind (under 12mph). Once you’ve got the right conditions you are set for a gorgeous day, walking through a sea of colour, identifying bumblebees. The great yellow bumblebee is a large bee, as the name suggests. It is usually yellow or yellow-brown in colour and has an obvious black band between the wings. Identifying bumblebees is slightly easier in Orkney as we only have eight species present - there are a total of 24 species in the United Kingdom, with 19 of these being found in Scotland.

 

Great Yellow Bumblebee Survey – Becky Austin

Over the past four years we have monitored the great yellow bumblebees and the results look positive, although it is too early to say what has triggered these results. At Brodgar, five times as many bees were recorded in 2017 than in 2015 and Copinsay and Onziebust have more than doubled their records in the same time. This year’s exceptional weather has resulted in more bees being recorded this year than in the previous three years put together. This doesn’t mean that we can relax our conservation work and the great yellow bumblebee will remain a high priority species for the RSPB in Orkney and elsewhere.

 

Give nature a home – Becky Austin

Are you a landowner or land manager who is interested in helping the UK’s rarest bumblebee? Do you have an area of land that you would like to manage as a species-rich grassland? Or have you noticed that somewhere on your land is already really good for great yellow bumblebees? We'd love to hear from you, please contact Christine Skene on Christine.skene@rspb.org.uk to discuss management further or to report an area where you already have great yellow bumblebees.

If you have a garden there is still plenty you can do for bumblebees. To find out more follow the link below:

https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/other-garden-wildlife/insects-and-other-invertebrates/bees-wasps-ants/bumblebee/

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