We had a great time talking photography and watching numerous warblers and other songbirds move through the nearby trees. As a bonus, the cement pad at the hill's crest served as an attractant to hill-topping butterflies of many species.
The silken tents in which the animals live communally until their last instar serve several purposes. Foremost, the dense sticky silk offers superb protection from would-be predators, especially parasitoid flies and wasps. Both are prolific enemies of caterpillars. Also, most songbirds will not deal with the dense silk, so for the most part the caterpillars are also safe from the feathered crowd.
Come nightfall, and the temporary disappearance of most of the birds, flies, and wasps, the caterpillars emerge from the nest and radiate out into the tree to feed on cherry foliage. Come dawn, they crawl back into the shelter of the nest. The tent probably also serves as a sort of greenhouse, with an elevated internal temperature that speeds the digestive process of the caterpillars within. Note all of the little blackish flecks in the silk - that is all frass, or caterpillar poo.
Most birds do have trouble eating them, as the long stiffish bristles of the caterpillar will eventually clog up their digestive tracts. Most famous of the tent caterpillar-eating birds are the cuckoos, who seemingly eat them with impunity. This is because Black-billed and Yellow-billed Cuckoos can slough off and cast out their stomach linings if they become too spiked with caterpillar bristles. The bird is able to regrow its stomach lining and thus can regularly consume the bristly meals. For the most part, with at least one notable exception, it seems to be the cuckoos that are the primary avian predator of eastern tent caterpillars.
Dane, with his mega lens and skills at finding objects through blowing leaves and branches, managed a great series of shots, and he was kind enough to share them with us. In the photo above, the oriole has just alit and is inspecting the nest for victims.
We can see in the above photo that the oriole has apparently pierced the skin of the caterpillar, and is drawing out the prized innards.
Even the most reviled native animals, such as tent caterpillars, have value. Our superficial condemnation is often unjustified and all too frequently based on ignorance.
Thanks to Dane for sharing his great series of photos.