The National Bumblebee Nest Survey

Home page Report Bumblebee identification key at the Natural History Museum

Bumblebee (Bombus hypnorum) colony in a bird nest box in a Hertfordshire garden. Photo: J. Osborne.

Where Bumblebees live

Bumblebees are fascinating and important insects. They live in annual colonies, feeding on nectar and pollen, and they provide an important pollination service for many of our fruit and vegetable crops, as well as wild flowers. Most gardens are frequented by at least one species of bumblebee; and the public are becoming more aware of the need to conserve and encourage these busy animals. Over the last 100 years, many bumblebee species have declined in the UK, particularly in arable areas. The decline is thought to be linked to the impact of modern farming methods on bumblebees' food plants. But as well as food, bumblebees need nesting sites for queens to start new colonies in spring. It is therefore important to safeguard habitats where the bees nest, as well as providing floral resources for them. To find out how important different habitats are for bumblebee nesting we asked the public to take part in the National Bumblebee Nest Survey in 2004. The results have been published this summer in the British Ecological Society's Journal of Applied Ecology (Osborne et al., 2007) and show clearly that Britain's gardens are vital habitats for nesting bumblebees. The survey was developed as part of a project on bumblebees in the landscape, funded by the UK's Biotechnology and Biological Sciences Research Council.

More than 700 volunteers took part in the National Bumblebee Nest Survey to record the presence or absence of nests in defined areas of gardens, short grassland, long grassland and woodland, and along woodland edges, hedgerows and fencelines. The results show that gardens contain high densities of bumblebee nests (36 nests per ha), and so do hedgerows, fence lines and woodland edges (20-37 nests/ha). Nest densities were lower in woodland and grassland (11-15 nests/ha). This is the first estimate of bumblebee nest densities in different habitats in the UK, and will help guide management initiatives to promote their conservation.

Bumblebee entering her colony in a plastic compost bin in a Scottish garden. Photo: J. Alexander.

Gardens provide attractive nest sites for bumblebees for many reasons. The diversity of garden features and gardening styles provide a large variety of potential nesting sites compared to more uniform countryside habitats. Areas with gardens have a high concentration of boundary features, such as hedges, fences, and garden buildings, which are suitable for nesting. Bumblebees also like nesting in compost heaps, bird boxes and flower beds. Gardeners like to see flowers almost all year round, so this ensures continuity of nectar and pollen sources for the bees throughout spring and summer at a density rarely encountered in the countryside.

Bumblebees' penchant for nesting in linear habitats in the countryside is less easy to explain. It could simply be because bees are confined to these habitats in heavily cultivated areas, or relate to the fact that bees use landmarks like hedges for navigation. Bumblebees are known to use linear features such as hedgerows to guide their foraging activity and queen bumblebees may found more nests in or near linear features because they could act as conspicuous linear landmarks to help them get back home. Although in the countryside the total area occupied by field margins and hedgerows is relatively small, current farm stewardship schemes in the UK are likely to facilitate bumblebee nesting, because they provide clear guidance and support for sympathetic hedgerow management and field margin management.

The findings will help conservationists understand – and hopefully address – the factors responsible for declining bumblebee populations. As well as providing important information on which habitats are the most important for bumblebee nests, the study also shows what a valuable contribution members of the public can make to ecological research. The scientists were delighted that so many people volunteered to do the survey and the success of the survey shows that public participation is very useful for monitoring bumblebees. If people want to learn more about bumblebees, and encourage them into the garden, they can join the Bumblebee Conservation Trust at bumblebeeconservation.org, which provides lots of information and bee-friendly ideas. This site also has details of further surveys which the public can take part in to help build a clearer picture of bumblebee populations in the UK.

Links

• A more detailed Volunteer's Report in Adobe Acrobat PDF format. Download the PDF viewer from here
• BBC News Online article - "Gardens 'vital' for UK bumblebees "
• Guardian Unlimited - "Plea to gardeners: keep a little patch unclipped to help save bumblebees"
• bumblebeeconservation.org

Reference

J L Osborne et al. (2007)*. Quantifying and comparing bumblebee nest densities in gardens and countryside habitats. Journal of Applied Ecology, doi: 10.1111/j.1365-2664.2007.01359.x Published online on 23 July 2007.
Click here to view online

For further information contact juliet.osborne@bbsrc.ac.uk or andrew.martin@bbsrc.ac.uk