My beebath

Seems my birdbath has turned into a beebath. Or maybe a bee drinking well. Hopefully you can see the little critters here. They have been downright testy when the birds come to drink or splash around. In fact, I've seen several birds get chased away. Some birds, like the robins, will try to snap at them but they always lose out. This has been a problem since I put it out a couple years ago but only in summer. I'm assuming they're desperate for water but why? Am I the only one with a water source in the neighborhood??