A light buzz year

As part of the Back from the Brink  (BftB) Shrill Carder Bee Project, I was recently invited to a Shrill Carder Bee Working Group meeting by the Bumblebee Conservation Trust. Those that know me will know that this species is a passion of mine and formed a key part of my PhD studies. The Working Group is carrying out a critical review of current understanding in relation to the conservation of the species in the UK. The aim being to identify gaps in understanding and develop a Species Recovery Plan. Following a few chats and requests related to this project, I have now made it a bit easier to track down my PhD thesis.

My PhD studies were funded by the Veolia North Thames Trust (formerly the Cleanaway Pitsea and Canvey Marshes Trust) and were an investigation of two species of bumblebee: the brown-banded carder bee (Bombus humilis) and the shrill carder bee (Bombus sylvarum). Both species were designated as UK Biodiversity Action Plan Priority Species having suffered significant historic declines in the UK. At the time of my studies, both species were limited to a handful of metapopulations across the country. One of these metapopulations was in the East Thames Corridor (South Essex and North Kent) and the project was an investigation of why the populations were able to persist in these areas. Studying their habitat use, and spatial movements within the landscape is critical to developing the understanding needed to restore habitat for these species on a landscape scale.

Brown-banded carder bee (Bombus humilis) by Stuart Connop

Maps were produced of the South Essex distributions of the bees and a combination of field surveys, pollen sampling, habitat manipulation and microsatellite DNA analysis were used to investigate the forage requirements, nesting preferences and spatial dynamics of the bees. Bombus humilis and B. sylvarum queens were recorded as the latest emerging of the Bombus species observed, not appearing until late May. Fabaceae, Scrophulariaceae and Lamiaceae were recorded as being the floral families most frequently and consistently visited by the bees with pollen being most commonly collected from Fabaceae and Scrophulariaceae.

Rarefaction analysis of dietary preference data revealed that the mean number of plant species B. sylvarum workers would be expected to visit during 20 flower visits was significantly fewer than for B. humilis and B. pascuorum (p=0.009 and p=0.004 respectively). The mean number of plant species B. humilis would be expected to visit during 20 flower visits was similar to that of the nationally ubiquitous species B. pascuorum and B. lapidarius but was consistently lower than another ubiquitous species B. terrestris/lucorum, although not significantly so (p=0.182).

Shrill carder bee (Bombus sylvarum) by Stuart Connop

Forage patches sown with favoured forage species of the bees (Lotus glaber, Odontites verna, Ballota nigra, Lotus corniculatus and Trifolium pratense) successfully attracted B. humilis and B. sylvarum workers. No technique was found for reliably locating nests, and only three nests were located in the study. Those that were found were situated in relatively undisturbed tall rough grassland with a sunny exposure.

A field full of perfect forage for the brown-banded and shrill carder bees. Created at Hadleigh Park by green haying. By Stuart Connop

For the first time, microsatellite DNA analysis was used to assess foraging

distances of rare bumblebees. Mean minimum foraging distances estimated from distances separating sister bees were calculated as 756 m for B. humilis and 232 m for B. sylvarum. These distances were considered to be appropriate spatial scales for nesting and foraging habitat management. Results from this study were fed into a 10-year habitat management program for the bees at Hadleigh Park, South Benfleet, Essex.

Trying to unravel the mysteries of bumblebee movements in the landscape using mark-recapture. Part of the Roscommon Way Study. By Stuart Connop

Whilst my research focus now has expanded to take a more holistic approach to habitat creation for biodiversity, particularly in an urban context, I still take a keen interest in the plight of these two species. That includes remaining involved in research projects in South Essex investigating best practice for habitat creation for the bees, including a long-term monitoring project at Hadleigh Park. All of the papers and reports from these projects can be found on the UEL research repository along with all of the other publications from the UELSRI team.

With declines in both of these species ongoing in the UK, particularly so for the shrill carder bee, such research is more important than ever. We are hoping that the work of the Bumblebee Conservation Trust and Buglife, as part of the BftB Shrill Carder Bee Project, combined with the input of all of the other partners that attended the Shrill Carder Bee Working Group meeting, will lead to a strong Species Recovery Plan being developed. This will bring together and consolidate current understanding, and identify gaps in understanding as foci for future research efforts. Such collaborative initiatives are vital if we are to ensure that we continue to experience this beautiful species across our landscapes for a long time to come.

By Stuart Connop