I watched a bumblebee 'work' multiple flowers of a rhododendron early this morning. The flowers were beautiful and freshly open. It was head deep in a flower at times, using its legs to collect pollen. Watching different kinds of bumblebees visit flowers is fascinating.
Here, the small claw is visible at the end of the extended leg, in an unusual position for a bumblebee!
Depending on the flower's shape and size, and whether they're collecting pollen or nectar, they can hang around individual flowers gleaning lots of pollen, shoving it into their pollen baskets, or rapidly collect nectar and move on.