2.2 Bee behaviour and Visitation Rates
To test if robbing leads to altered behaviour of bumblebees, we recorded
several aspects of visitation. Firstly, we tested whether robbing would
cause a change in visitation rates, by quantifying the number of visits
per flower per hour on plants in both treatments when in full bloom. We
also recorded the identity of bumblebee species that visited when
conducting censuses. Plants were arranged in a line, separated by about
1 meter, with alternating treatments and the individuals within each
treatment had their positions randomised. We recorded counts of each
bumblebee species visiting flowers on control and robbed treatment
plants and used 644 3-minute censuses to quantify visitation rates in
3-hour periods that covered different times of the day when floral
visitors were active. Secondly, we also measured potential effects of
robbing on the duration of floral visits by bumblebees. We recorded with
a stopwatch the length of visits to individual flowers, defined as the
time between entering a flower to feed and appearing at the mouth of the
corolla to exit it.
Bumblebees typically visit several flowers on a foxglove inflorescence
in each foraging bout, so to test whether robbing had an effect on a
continuous foraging bout we measured the proportion of flowers on an
inflorescence that individual bumblebees visited per foraging bout.
Finally, we also recorded the number of times a plant in a treatment was
‘rejected’, defined as a bumblebee hovering near flowers and leaving
without landing, or landing on the flower and leaving without entering.