"To explore how early and under which light levels colonies of buff-tailed bumblebees initiate their foraging activity, the researchers tracked foragers of different body sizes using RFID — similar technology to contactless card payments — over 5 consecutive days during warm periods of the flowering season.
They found that most foragers left at higher light levels when they could see well and fly faster.
Nevertheless, a small proportion of foragers left the colony shortly after the onset of dawn when light levels were below 10 lux.
According to the team, bumblebee vision is poor in low light, so flying at dawn or dusk raises the risk of getting lost or being eaten by a predator.
However, the bees benefit from extra foraging time and fewer competitors for pollen in the early morning.
“Larger bumblebees have bigger eyes than their smaller-sized nest mates and many other bees, and can therefore see better in dim light,” Hall said."