Once it gets dark it would nothing to see 20-30 toads siting in front of the hives. Given half a chance they somehow jump up and get their foot into the entrance and then just sit there picking bee by bee from within the entrance.
I'm going to setup a new bee stand over the weekend for my growing collection of hives. This time I am going to have the cinder blocks on their sides to keep the hives lower. I'm going to try using a plastic barrier/fence around the hive stand to stop the toads getting in. I don't know this will work, but worth trying.