Honeybees Push and Chase Other Pollinators Away From Flowers

Honeybees do more than reach a flower first. Researchers in England have recorded them pushing and chasing other insects off blooms so they can keep the nectar and pollen for themselves. It is the first detailed evidence of how often honeybees interfere with other species' food.

Ninety-three hours of watching flowers

The study was carried out by researchers at Anglia Ruskin University and published in the journal Ecological Entomology. Over two years the team watched insects at five locations in and around Cambridge, England. Every site sat within 300 metres of an established honeybee colony, so honeybees were always nearby.

The flowers chosen were bramble and ivy, two plants that produce plenty of nectar and pollen and draw large numbers of insects while they are in bloom. Visitors were sorted into five groups: honeybees, which live in colonies; bumblebees; solitary bees, which nest alone instead of in hives; hoverflies, flower-visiting flies that are often mistaken for bees; and an other group covering butterflies, beetles and wasps. Across more than 93 hours of observation, the scientists logged every encounter in which one insect interrupted another's feeding or blocked its way to a flower, and marked each one as a win, a loss or a share.

Who won, and who was pushed aside

Places with more honeybees generally had fewer other pollinators, and more squabbling over flowers. On bramble, doubling the number of honeybees went together with a 14% drop in bumblebees. On ivy, higher honeybee numbers were linked to fewer solitary bees and hoverflies.

The honeybees were not merely early. Other pollinators actively avoided them in 28% of the encounters recorded on bramble and 36% of those on ivy. In at least one in five of the encounters that honeybees won, on either plant, they physically shoved or chased the other insect away. Aggression started by other species was rare.

There was one exception. The ivy bee, a solitary species that is not native to Britain and was first recorded in the country in 2001, was the only pollinator seen actively taking on honeybees. It sometimes chased or displaced them and reached the flowers anyway.

Warmer weather, more hives

Competitive encounters became more frequent when conditions were warmer. One possible reason is that plants suffering heat stress, meaning they get too hot, can make less nectar, leaving more insects to compete over a smaller supply of food. Temperature also affects pollinators differently: bumblebees and hoverflies are sensitive to high temperatures and may feed better in cooler weather, while honeybees generally become more active as it warms. Earlier research found that raising the temperature by 12 degrees Celsius produced a tenfold increase in the number of honeybees leaving their nests.

Meanwhile, beekeeping in the UK has grown. The number of registered beekeepers rose from 19,000 in 2010 to 47,000 last year.

Lead author Victoria Buckle, a PhD student at Anglia Ruskin University in Cambridge, said the aim of the study was not to discourage beekeeping but to understand how competition between wild and managed pollinators happens, so that wild pollinators, which play an important ecological role, can be conserved.