Crofting and bumblebee conservation: the impact of land management practices on bumblebee populations in northwest Scotland

Published source details Redpath N., Osgathorpe L.M., Park K. & Goulson D. (2010) Crofting and bumblebee conservation: the impact of land management practices on bumblebee populations in northwest Scotland. Biological Conservation, 143, 492-500.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Plant wild bird seed or cover mixture Action Link
	Provide or retain set-aside areas in farmland Action Link
	Plant nectar flower mixture/wildflower strips Action Link

Plant wild bird seed or cover mixture

A replicated controlled study in summer 2008 in northwest Scotland (Redpath et al. 2010) found that croft sections (an agricultural system specific to Scotland, consisting of small agricultural units with rotational cropping regimes and livestock production) sown with a brassica-rich ‘bird and bumblebee’ conservation seed mix had 47 times more foraging bumblebees than sheep-grazed sections and 16 times more bumblebees Bombus spp. than winter-grazed pastures in June. In July the ‘bird and bumblebee’ mix sections had 248 and 65 times more bumblebees than sections grazed by sheep or both sheep and cattle respectively. The number of bumblebees in July was also significantly higher (4-16 times) in ‘bird and bumblebee’ sections than in arable, fallow, silage, and winter-grazed pasture sections. The availability of bumblebee forage plant flowers was lower in ‘bird and bumblebee’ sections than in silage sections in June, but no other significant differences involving the conservation mix were detected. Plant species in the legume (Fabaceae) family were the most frequently visited by foraging bumblebees. Tufted vetch Vicia cracca was one of a few plant species favoured by bumblebees and was predominantly found in ‘bird and bumblebee’ sections in July-August, although it was not part of the seed mixture. Thirty-one crofts located on Lewis, Harris, the Uists and at Durness were included in the study. The ‘bird and bumblebee’ conservation mix was sown for several bird species and foraging bumblebees, species sown included kale Brassica oleracea, mustard Brassica spp., phacelia Phacelia spp., fodder radish Raphanus sativus, linseed Linum usitatissimum and red clover Trifolium pratense. In addition to the seven management types mentioned, unmanaged pastures were surveyed for foraging bumblebees and bumblebee forage plants along zigzag or L-shaped transects in each croft section once in June, July and August 2008. Foraging bumblebees 2 m either side of transects were identified to species and recorded together with the plant species on which they were foraging. Flowers of all plant species were counted in 0.25 m² quadrats at 20 or 50 m intervals along the transects.
Provide or retain set-aside areas in farmland

A replicated controlled site comparison in summer 2008 in northwest Scotland (Redpath et al. 2010) found that croft sections in fallow had nine times more foraging bumblebees than croft sections grazed by sheep and cattle in July. In August there were more foraging bumblebees in fallow sections than sections with a silage crop, but fewer than in sections sown with a bird and bumblebee conservation seed mix. Red clover Trifolium pratense and greater knapweed Centaurea nigra were two of few plant species favoured by bumblebees and were predominantly found in the fallow sections July-August. Thirty-one crofts located on Lewis, Harris, the Uists and at Durness were included in the study. In addition to the four management types mentioned, arable crops, unmanaged, sheep-grazed and winter-grazed pastures were surveyed for foraging bumblebees and bumblebee forage plants along zigzag or L-shaped transects in each croft section in June, July and August 2008. Foraging bumblebees 2 m on either side of transects were identified to species and recorded together with the plant species on which they were foraging. Inflorescences of all plant species were counted in 0.25 m² quadrats placed at 20 or 50 m intervals along the transects.
Plant nectar flower mixture/wildflower strips

A replicated controlled site comparison study in summer 2008 in northwest Scotland (Redpath et al. 2010) found that croft sections (an agricultural system specific to Scotland, consisting of small agricultural units with rotational cropping regimes and livestock production) sown with a brassica-rich ‘bird and bumblebee’ conservation seed mix had 47 times more foraging bumblebees Bombus spp. than sheep-grazed sections and 16 times more bumblebees than winter-grazed pastures in June. In July the ‘bird and bumblebee’ mix sections had 248 and 65 times more bumblebees than sections grazed by sheep or both sheep and cattle respectively. The number of bumblebees in July was also significantly higher (4-16 times) in ‘bird and bumblebee’ sections than in arable, fallow, silage, and winter-grazed pasture sections. The availability of bumblebee forage plant flowers was lower in ‘bird and bumblebee’ sections than in silage sections in June, but no other significant differences involving the conservation mix were detected. Foraging bumblebees most frequently visited plant species in the legume (Fabaceae) family. Tufted vetch Vicia cracca was one of a few plant species favoured by bumblebees and was predominantly found in ‘bird and bumblebee’ sections in July-August, although it was not part of the seed mixture. Thirty-one crofts located on Lewis, Harris, the Uists and at Durness were studied. Species sown in the bird and bumblebee mix included kale Brassica oleracea, mustard Brassica spp., phacelia Phacelia spp. and red clover Trifolium pratense. In addition to the seven management types mentioned, unmanaged pastures were surveyed for foraging bumblebees and bumblebee forage plants along zigzag or L-shaped transects in each croft section once in June, July and August 2008. Foraging bumblebees 2 m either side of transects were identified to species level and recorded together with the plant species on which they were foraging. Flowers of all plant species were counted in 0.25 m² quadrats at 20 or 50 m intervals along the transects.