Responses in honeybee and bumblebee activity to changes in weather conditions

Abstract

Insect pollination by both managed and unmanaged bees is a highly valued ecosystem service that ensures plant reproduction and the production of high-quality crops. Bee activity is known to be influenced by the weather, and as the global climate continues to change, the flying frequency and foraging behaviour of bees may also change. To maximize the benefits of pollination in a changing world we must first understand how current weather conditions influence the activity of both unmanaged and managed bees. This is of particular interest in a country such as Ireland where inclement weather conditions are nominally sub-optimal for foraging. We observed honeybee (Apis mellifera; largely managed) and buff-tailed bumblebee (Bombus terrestris; largely unmanaged) colonies across a variety of weather conditions within seven apple orchards to determine how four weather variables (temperature, relative humidity, solar radiation, wind) influence the flight activity of each species. Our results indicate bumblebees could compensate for low honeybee activity in inclement conditions, which supports the theory that pollinator diversity provides resilience. This may be particularly important in management of pollinators in crops that flower in the spring when weather is more variable. We found pollen-foraging individuals in both species increase with temperature, but this rate decreases with humidity. On the whole honeybees are more sensitive to changes in weather than bumblebees and could be more predisposed to changes in future within-day weather conditions.