What is this noise?

I’m in Spain right now (around Valencia) on a campus with a lot of trees, and there’s this noise that starts around dusk and goes on through nightful. It sounds like a dying cat, but people are insisting that its some sort of bird.

I thought that it was a catbird, but I don’t think they live in Spain, and it doesn’t really sound like one anyway.

Any ideas?

It’s not really like a “mew”, like this site has as a sample of the sound of what I previously thought it was.

It’s more like a meeeeee-owwwww, meeeeee-owwwwwww. meeeeee-owwwwwwwwwwwwwwww. And it keeps going up in pitch – it’s giving me a headache, honestly.