I agree with Chris. But a good indication as to whether or not they need rescuing..... are there any dead toads? I know that sounds morbid, but we used to have the same issue when we lived in the country. We'd find toads and salamanders in there. I also found a couple dried out toads, which obviously means they couldn't get out. Ultimately, if you're concerned about it, I think Chris' idea of stacking a few stones or bricks in there could help. If you want to go a step further, you could cover your window wells with some chicken wire or a clear plastic cover.