I saw the same thing today at my hives. I figured they may be feeding on the dead bees in front of the hive or picking at what they can get off the bottom. If the bees don't seem worried, I wouldn't be either
Flies? Problem?
Our first warm, sunny, calm day!!! 
I have one 3 year old hive in the back yard that is awake and flying. During February and March when we had some warmer days I had seen bees coming out to "freshen" up a bit, so all seems well.
However, today there are also lots of flies around the hive opening, sitting on the landing board, and clinging to the cement blocks I use as a hive stand. Lots of bees coming and going (loaded with yellow pollen too!) and they seem to be ignoring the flies. Should I worry about these visitors? There is still sugar on top of the hive from mountain camp feeding, could that be the attractant? I've not seen flies before in or around the hive.
I have one 3 year old hive in the back yard that is awake and flying. During February and March when we had some warmer days I had seen bees coming out to "freshen" up a bit, so all seems well. However, today there are also lots of flies around the hive opening, sitting on the landing board, and clinging to the cement blocks I use as a hive stand. Lots of bees coming and going (loaded with yellow pollen too!) and they seem to be ignoring the flies. Should I worry about these visitors? There is still sugar on top of the hive from mountain camp feeding, could that be the attractant? I've not seen flies before in or around the hive.
