Providing evidence to improve practice

Individual study: Bumblebees Bombus spp. use forage plants sown on field margins as a pollen source, at Manor Farm, Eddletorpe, North Yorkshire, England

Published source details

Carvell C., Westrich P., Meek W.R., Pywell R.F. & Nowakowski M. (2006) Assessing the value of annual and perennial forage mixtures for bumblebees by direct observation and pollen analysis. Apidologie, 37, 326-340

Background

Some bumblebee species Bombus have dramatically declined in Europe, and modern intensive agricultural practices are a suspected cause. This study assesses the value of three seed mixtures, available as options under the UK Environmental Stewardship Scheme, in providing pollen resources for foraging bumblebees at Manor Farm, Eddlethorpe, North Yorkshire, England.

Action

Five 30 m x 6 m plots of each of three seed mixtures were sown on the margin of a large arable field, on 17 April 2001. The mixtures were: two perennial grass and wildflower mixes - ‘basic’ with three herbaceous species (black knapweed Centaurea nigra, bird’s-foot trefoil Lotus corniculatus and red clover Trifolium pratense) and ‘diverse’, with 18 herbaceous species - and a mix of annual cover crops including borage Borago officinalis, fodder radish Raphanus sativus and yellow-blossomed clover Melilotus officinalis.

The perennial mixes were cut three times in 2001 and twice (early April and late August) in 2002, to aid establishment. The annual mix was re-sown in March each year, after ploughing.
Foraging bumblebees were recorded in a 30 m x 4 m wide transect in the centre of each plot, on 12 dates between 28 May and 20 August 2002 and seven dates between 14 May and 11 August 2003, between 09:30 h and 17:00 h in dry weather with temperatures above 15°C.
Pollen loads were collected from 40 buff-tailed bumblebee Bombus terrestris and 105 common carder bee B. pascuorum workers foraging in the plots on 10, 11 and 12 July 2002. Their composition was determined to plant species or family.

Consequences

Total bumblebee abundance was highest on annually sown plots. Short-tongued bumblebee species B. terrestris, B. lucorum and B. pratorum strongly preferred the annual seed mixture. Long-tongued bumblebee species Bombus hortorum and B. pascuorum preferred the perennial seed mixtures, but were not more abundant on the ‘diverse’ than the ‘basic’ mix. Six common bumblebee species were recorded.

On average, 88% of B. pascuorum pollen loads and 73%of B. terrestris loads came from plant species sown in the plots. 75.6% of the pollen loads from B. pascuorum was red clover pollen, while 69.6% of pollen loads from B. terrestris was borage pollen.
Note: If using or referring to this published study, please read and quote the original paper, the abstract of which is can be viewed at: http://www.apidologie.org/