David Eyre mentioned the fun of watching bees
take pollen.  I have used one of the small
bird feeders that attaches directly to a window
with suction cups to feed pollen substitute in the winter.
On good flying days, one can watch all the
behavior close at hand.  It helps if its
mounted on a south facing window.  Mine is
colored yellow to attract the first scouts.
Re filling is simple, best done at night.
Wayne Esaias
Highland, MD.