As Kim says they are probably trying to get to their spawning pond.
We have loads of frogs and toads in the garden. A few newts as well. The pond is packed with spawn and they're still making an almighty racket at night so goodness knows how much more will be there by the time they've finished their shenangans.
They are about the only thing the cats won't kill so if the dragonfly lavae don't get them at tadpole stage they are free to take over the garden!