@datarama
i dont really hike, but I wouldn't associate frogs with trees.
The list page listed "european tree frog".
I thought amfibs like that lived in Amazon delta or north Aus jungles or something .
@channelOwen The only continent that doesn't have tree frogs of some kind is Antarctica. :-)
They do require humidity (like all frogs, they drink through their skin and can dry to death), and they have to find a freshwater pool to reproduce, but they often live in light woodland areas near ponds and lakes. They generally avoid dark forests because they need sunlight to stay warm.
The European ones (at least the North European ones; I'm less familiar with the others) don't usually climb tall trees, but usually stick to low trees, bushes and the like. They are preyed on by birds and grass snakes.
This is what they sound like:
https://www.youtube.com/watch?v=CYxBEhl_VPw
I don't know if I'd call it warbling, but they do mainly call out in the spring - that's their mating season. Usually the males show off their vocalization skills both to serenade females (who seem to mostly be attracted to males by their voices, rather than their looks!), and to upstage each other. (They do sometimes fight, but a lot of frog disputes are settled by croaking contests.)