A study supported by the Game & Wildlife Conservation Trust (GWCT) has identified the most desirable nesting sites for the UK’s declining population of solitary bees and recommended simple measures to support them.
As their name suggests, solitary bees do not live in colonies like bumblebees and honey bees, with some species preferring to nest in the ground. While their foraging behaviour and preferences have been studied, little has been known about the type of sites they prefer to nest in, until now.
Britain has almost 250 species of solitary bee, but population numbers have declined over the past decade. Many of them are important pollinators for crops like apples, pears and strawberries. The study, by University of Sussex PhD student Rachel Nichols, supported by the GWCT, set out to determine whether nesting habitats for ground-nesting solitary bees could be created as small plots on the edge of farmland to aid the declining population, and whether or not the bees would move in.
Across Europe, agri-environment schemes (AES) have been developed to encourage wildlife friendly farming by providing landowners with financial support for conservation. Creating suitable habitats on farmland has not yet been included in any AES but could be introduced to help support the number and diversity of ground-nesting solitary bees.
At 19 locations across four Hampshire farms, Rachel compared small plots scraped bare using machinery, sprayed with herbicide, or left undisturbed. The locations were chosen by finding compacted ground (such as vehicle routes at the edges of fields) with a slight slope and on the south side of hedgerows or trees. The plots were surveyed once a month from April to July 2019. The greatest number of bee nests were found on the scraped plots.
Professor John Holland, Head of Farmland Ecology at the GWCT, said: “The study found that the bees preferred to nest in the plots that had been scraped bare. These scrapes can be quickly and cheaply made with farming machinery on the uncropped strips at the edges of field. Being simple and low cost to create, they could easily be included in any country’s agri-environment scheme to increase potential nesting sites for solitary bees and wasps and help support these useful pollinators.”
A summary of the report is available at: www.gwct.org.uk/farming/research/pollinators/bare-ground-on-farmland-provides-nesting-habitat-for-ground-nesting-solitary-bees