 And after they leave the nest, the parents continue to feed them caterpillars for another 21 days. And after they're independent from the parents, they continue to eat caterpillars. They don't eat seeds until the wintertime. And that's one bird. 96% of our terrestrial birds rear their young on insects, and most of those insects are caterpillars. So if you simply look at birds, caterpillars become essential.