A major factor controlling the population of pollinators (bees, bumblebees and hover flies) is the availability of nectar bearing flowers.  When and where nectar-bearing flowers are to be found is important.   A recent study  (Timberlake et al at Bristol Uni) looked at the availability of nectar and pollen supply and the colony density of buff tailed bumblebee [Bombus terrestris] colonies - by studying the different resources available on twelve farms in South West England.

The study found :

• The nectar supply in early autumn (September) was strongly correlated with colony density in the following Spring.
• The number of gardens in the area available to the bumblebees was also associated with colony success in the Spring.
• It was thought that improving the ‘quality’ of the semi-natural habitats would improve the availability of late summer / early autumn nectar supply.  

It is believed that a ‘resource bottleneck’ for bumblebees  / pollinators often develops in farmland areas in late summer. To overcome this ‘bottleneck’, a number of strategies might be used to support pollinators :

• Changing the ‘mowing regimes’ around the field margins so that wild flowers actually flower later.
• Planting or sowing late flowering species such as red clover or encouraging late flowering plants like Ivy.
• Encouraging rural gardens.