Where were bumblebee nests most densely found in the UK?

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Bumblebees provide important pollination services to crops and wild plants. Many species have declined in the UK, particularly in arable regions. Their forage requirements have been widely studied, but whether the availability of nesting sites is limiting has received less attention. Knowing which habitats have the most nests per unit area can guide conservation and management, especially given the emphasis on environmental stewardship schemes for farmed landscapes. Yet mapping bumblebee nest distribution is extremely difficult.

The National Bumblebee Nest Survey was a structured survey carried out by 719 volunteers in the UK during early summer 2004. Using a defined protocol, surveyors recorded the presence or absence of nests in prescribed areas of gardens, short grassland, long grassland and woodland, as well as along woodland edges, hedgerows and fence lines. These records enabled the first estimates of nest density in each of these habitats.

Estimated densities were high in gardens, at 36 nests per hectare, and in linear countryside habitats—fence lines, hedgerows and woodland edges—at 20–37 nests per hectare. They were lower in non-linear countryside habitats, woodland and grassland, at 11–15 nests per hectare. Findings about nest location characteristics corroborated an earlier UK survey by Fussell and Corbet in 1992.

Conclusions and applications: Gardens provide an important nesting habitat for bumblebees in the UK. In the countryside, linear features occupy less area than non-linear features. But because linear features have high nest densities, management affecting them may have a disproportionately large effect on bumblebee nesting opportunities. The authors concluded that current UK farm stewardship schemes are likely to facilitate nesting because they provide clear guidance and support for sympathetic management of hedgerows and field margins.