I have also noticed the bees in my girls feed. Had a bee guy come out and help me understand why they are there. He also said that since we have had tons of rainy days the bees need an alternate source of food. Since my girls are still eating and drinking I have decided to do nothing. Their numbers have also gone down but there are a few hangers on. Mine are wild honey bees and our neighborhood needs the help with gardens and such. I hope they make it through the winter.
Heavy rain will wash out the pollen and nectar from the flowers. Depending on the kind of flower it can take days to weeks to recover. The bees use the pollen as a source of protein.
Hi and welcome to BYC from northern Michigan It is good of you to leave the bees, they are having a hard enough time as it is with chemicals decimating their numbers. Most honeybees are very non-aggressive and are unlikely to hurt you or your birds.