This is my distinct memory too but I'm never sure how to separate it from the confounding factors of moving across the country and changing economic levels.

My childhood in the South was spent in a cacophany of frogs, birds, and cicadas. We'd have to yell at each other on the back porch to be heard over the treefrogs. Everywhere you looked was a reptile, bug, or other critter. Throw a hook in the water with a piece of bread or worm on it, and you'd have a bite nearly instantly.

Today, here in the Pacific Northwest, the forests are beautiful but almost entirely silent aside from a bird here and there. The last time I went camping, I didn't see a living thing larger than a banana slug. Much of that is surely the temperature difference, but I'm never sure if that explains all of it.