The Birds and the (Carder) Bees

I was in the garden trying to spot a sparrowhawk that had flown into one of our trees when my attention was drawn to a frenetic high pitched buzzing sound coming from the potentillas.  A male Carder Bee had landed on the thorax of a female and was buzzing loudly against her as a stimulation. The male then repositioned over her abdomen and proceeded to mate with her.  This was a first for me as I have never before seen bees mating.