It's really the sound of Spring, to hear the cuckoo - cuckoo - cuckoo from across the valley or somewhere through the trees. There are a lot of Cuckoos in Provence, but usually only to hear them, as they are very hard to see. If you do see a Cuckoo, it might be just a streak of bluish-grey flying low through the trees. Seen higher, the Cuckoo is similar to a Sparrowhawk, but has more pointed wings and a graduated tail with rounded end.
Just about anywhere in France (and western Europe), but especially in forests, fields and farmlands.