Barely Hanging On

Does anyone know why frogs would be attracted to our old single pane windows? I've never seen this before in previous homes, but this is the third frog in about as many days to suction himself to the outside of our wavy glass windows in the late evening.

It looks like the little guy is inside the house,

but that's just a reflection of the dining room. 

Our only guess is that the lights on inside the house are inviting to insects and the little amphibians are helping themselves to an easy dinner. But we can't substantiate our theory as we've never seen them eat anything. In fact, they barely move. They're just parked there for the night and gone in the morning. It's very curious!