I'm a newbee beekeeper, (one month and counting!). I have a screened bottom board, and have noticed lots of pollen pellets on the ground underneath. I have two hives and the other one has a regular bottom board. I don't notice any pollen pellets on the bottom of the board, so I'm assumming if they drop pollen, they can easily pick it back up off the board. Is it normal for bees to drop their pollen that much? Here is a pic of the ground underneath the screened board.
