This 2018 video says about itself:
African Emerald Cuckoo Eating Processionary Caterpillars
Female African Emerald Cuckoo in a Cross-berry Tree (Grewia occidentalis) eating Processionary Caterpillars, in a wildlife-friendly garden in KwaZulu-Natal, South Africa.
Translated from Dutch daily Trouw:
Brummen no longer fights oak processionary caterpillars with great tits: the money has run out
By Quirijn Visscher– 9:50, April 8, 2019
The oak processionary caterpillar is advancing. The municipality of Brummen also did not escape the dreaded caterpillar with stinging hairs that could cause serious health problems. The Veluwe village tried everything to dislodge the little tormentors. As environmentally friendly as possible. Last year, the municipality installed 60 great tit boxes in places with a lot of caterpillar nuisance, such as the stately oak lane at the De Engelenburg estate. It became a success.
The test nevertheless stops. The municipality of Brummen will not have the money in 2019 for it. That news hit hard with local nature lovers. The Brummen GroenLinks party branch decided to continue the campaign themselves, together with residents. “Some people were really angry that this trial was stopped by the municipality,” says GroenLinks party leader Hennie Beelen. The party managed to sell more than 140 nest boxes. “Surprisingly many.”
Brummen is not the only municipality that is experimenting with nest boxes. Throughout the country, municipalities are placing great tit boxes at strategic locations to give oak processionary caterpillars a natural enemy and to limit caterpillar nuisance. After all, sucking away caterpillars costs a lot of money. This method of control is similar to that of asbestos removal, with men in suits who must protect themselves against whirling stinging hairs.
Why did Brummen stop the trial? The simple answer: the municipality must make large-scale cuts in 2019.