May 13 2021

What’s the buzz on bees?

Our orchard volunteers at Hucking, Kent, have received some fantastic advice from the Bumblebee Conservation Trust when undertaking activities to increase biodiversity at the site. We thought we would share some of it here for interest. Perhaps if you are part of a Woodland Working Group you could look at how we can do more to attract our fuzzy, buzzy friends.

Thank you to Assistant Site Manager, Claire Inglis, and the BCT for sharing with us.

 

What do bumblebees need? 

 

Habitat 

Bumblebees, especially our rare and scarce species, are species of open, well-connected, flower-rich grassland and grassland-scrub habitat mosaics. These habitats have significantly declined and become increasingly fragmented over recent decadesShrill carder bees and Brown-banded bumblebees are particularly sensitive to inappropriate management of these habitats. As late-emerging species with colonies that persist into early autumn, their nest cycle coincides with operations such as hay-cutting, hedge trimming and road verge management. In addition, suitable nesting and forage habitat must be in close proximity as studies have shown that these species prefer to forage within 100-250m of nest sites.  

 

Nesting sites should be warm, sheltered and undisturbed. Many of our common and widespread bumblebee species nest in disused small mammal burrows underground. Many of our rare and scarce bumblebees are ‘carder’ bumblebees. These nest on or close to the surface of the ground in undisturbed long vegetation or in grass tussocks in sunny areasIdeally nesting habitat should be cut on a 2-3 year cycle to allow a denser sward to develop or managed by light grazing. 

 

Forage

Bumblebees need sugary nectar for energy and pollen for proteinUnlike honeybees, they only store a few days food at a time, so they need continuous flowers through the entire flight season (February to October)Our rare and scarce species are late emerging (May onwards). Abundant forage is critical throughout the colony cycle.  As new queens emerge from hibernation they must build up reserves lost over winter and establish a new colony. In late summer/early autumn the colony needs abundant forage available for development of new queens and for those new queens to build up fat reserves before hibernation. See table 2 for some key forage plants. 

 

Hibernation sites are often cool and north-facing with loose soft soil, e.g. hedge banks, woodlands, ditch banks, dead wood, or under stones. Bumblebees burrow down a few inches and excavate a small chamber in which to spend the winter. 

 

Look for further opportunities to increase coverage of wildflowers and to extend the flowering season. Identify areas to be managed as wildflower meadows which can be managed by an annual cut and collect and removal of cuttings. Introductions of yellow rattle seed to the proposed meadow areas may assist with the suppression of grasses to create an open sward of finer grasses and allow opportunities for other wildflowers to set seed and germinate. Yellow rattle introduction may need to be repeated in successive years until successful and well-established. 

 

Consider introduction of plugs or seed of plants with long-flowering seasons to help fill the gaps in forage provision. Suggestions for plants to introduce include red clover, white-dead nettle, red dead-nettle and black horehound. 

If growing long vegetation is not desirable, there are numerous options for increasing abundance of flowers in shorter swards. Low-growing species such as bird’s foot trefoil, red and white clover and selfheal would be ideal for sowing eg: between fruit trees in an orchard where vegetation needs to be managed.

 

Table 1 – A selection of key forage plant species for bumblebees 

Common Name 

Species 

Key Flowering Period 

Notes 

Comfrey 

Symphytum sp. 

EARLY SEASON 

March – June 

Excellent spring forage for queens. Grows well in many places including brownfield.  

White dead-nettle 

Red dead-nettle 

Lamium album 

Lamium purpureum 

EARLY– LATE SEASON 

May – December  

Excellent early & late forage for queens. Both plants have a long flowering season 

Birds-foot trefoil 

Lotus corniculatus 

MID-SEASON 

June – September 

Important source of nectar for workers.  

Bramble 

Rubus fruticosus 

MID SEASON 

June – August 

Mid-season forage source for workers & males.   

Hedge woundwort 

Stachys sylvatica 

MID– SEASON 

July – September 

Great for long tongued species such as Shrill carder bee 

Red clover 

Trifolium pratense 

MID– SEASON 

May – September 

Important high-quality pollen source 

Viper’s bugloss 

Echium vulgare 

MID-LATE SEASON 

May – September 

Excellent nectar source for medium and long tongued bumblebees including SCB 

Black Horehound 

Ballota nigra 

MID-LATE SEASON 

June – September 

Great for long tongued species such as Shrill carder bee. 

Common / Greater Knapweed 

Centaurea nigra / Centaurea scabiosa 

MID-LATE SEASON 

June – September  

Important source of nectar and pollen for workers.  

Common Fleabane 

Pulicaria dysenterica 

LATE SEASON 

July- September 

Important nectar source for males in particular 

Red Bartsia 

Odentites vernus 

LATE SEASON 

June – September 

Very important late forage source for workers, males and daughter queens.   

Nesting habitat recomendations:

Areas of vegetation left to grow long and kept undisturbed from trampling and mowing from April-September at the base of hedgerows and in field corners can provide opportunities for bumblebee nesting. Many bumblebees nest underground or in cavities in places where small mammals have previously nested. Bumblebees make use of the materials collected to create the insulation for their brood.  

 

Leaving areas of vegetation to grow longer and left undisturbed can encourage small mammals such as voles and mice and in turn create nesting opportunities for bumblebees. A mosaic of areas of longer and shorter vegetation will also help to create beneficial habitat for the reptiles present at the orchard.  

 

Consider creating a composting area or habitat piles of rocks and logs in warm, sheltered areas of the orchard to provide nesting locations for bumblebees and shelter and basking opportunities for reptiles and rodents. Having a location on site to place vegetation cuttings can provide flexibility for managing smaller areas of grassland. Bumblebees often find nest sites within these habitat piles and they are also commonly used by reptiles such as slow-worms and lizards for shelter and feeding sites. If loose habitat piles are considered untidy, wooden structures can look attractive and still provide the same benefits. Place a crisscross network of sticks and timber in the base of the heap to allow air to circulate and provide structure to the pile. The western end of the orchard at the bottom of the slope might be one ideal area for these habitats as these piles of can introduce nutrients into a concentrated area. Allow some nettles and other longer vegetation to grow up around the habitat piles 

 

Create nesting opportunities for cavity-nesting solitary bees by retaining dead wood in sunny locations and consider the addition of solitary bee nest boxes. These can be simple blocks of drilled wood (depth of holes at least 15cm and a variety of diameters from 2 – 10mm) or containers filed with hollow stems such as bamboo or reed stems.

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