For context, this happens regularly.

In Slovenia we have something similar with pine trees and caterpillars. Not that severe, though.

https://en.wikipedia.org/wiki/Oak_processionary

An experiment with bird houses for the great tit began in 2016. It has been observed that great tits like to eat the young, not yet hairy caterpillars in April.

That link leads to an article with the headline:

Germany battles aggressive outbreak of poisonous caterpillars