Oaks to Caterpillars to Birds

The National Wildlife Foundation has a county-level guide, the Native Plant Finder, to native plants that support caterpillars. Why caterpillars? Because they are esentially the foundation of the food chain for song birds. Even the seedeaters that come to your feeders for seeds and suet in winter feed their young caterpillars. Caterpillars are relatively soft as insects go, and they are simply packed with fats, proteins and carotenoids, which are vital for avian development and feather pigmentation.

The stats on caterpillar consumption are mind-boggling: a single nesting pair of Carolina Chickadees will feed their young ones 6000-9000 caterpillars before fledgling, meaning over sixteen days on average. After fledgling, nobody has counted, but fledged Chickadees get feed for up to three more weeks. It’s rare to see Carolina Chickadees in Brooklyn.

Here’s another: a Wilson’s Warbler pair were closely observed. The male carried food to the nest 241 times a day, the female 571 times a day. For five days. That’s a minimum of 4060 caterpillars, if each trip was one caterpillar’s-worth. Often as not there are more than one caterpillar in the parent’s bill, at least in places un-assaulted by chemical warfare and invasive species.

Bobolinks: parents brought food to nest 840 times a day for ten days in a row.

A UK study of ten different passerines found an average of 259 food trips to nest per day.

Audubon’s Plants for Birds is another good source for information on plants to grow in your area. Many of the plants sold for yards and gardens are the WORSE thing you could do for local food webs. After all, they’re for sale so people can make money. Pretty and exotic is sterile. Ornaments and decorations, it turns out, are actively working AGAINST nature.

“Bird-friendly” shade grown coffee? Nope, not if the shade is being thrown by eucalyptus trees, which are often used because they grow fast… and provide shade. But they provide next to nothing for the birds because they provide nothing for local insects.

(In California, where they went crazy for eucalyptus a century ago, precisely one species of insect has adopted to living off these exotic and invasive trees in that time.)

It’s not just biodiversity. The kind of plant makes a lot of difference. Some keystone species are disproportionately productive for food webs. “A landscape without keystone genera will support 70 to 75 percent fewer caterpillar species than a landscape with keystone genera, even though the keystone-less landscape may contain 95% of the native plant genera in the area.”

The single best insect-friendly species to plant in 84% of U.S. counties are white oaks and their relatives. They support some 934 caterpillar (butterfly and moth) species nation-wide. Compare with tuliptree (21 caterpillar species), black gum (26), Sweetgum (35), persimmon (46), and hemlock (92). In the mid-Atlantic states, white oaks host nearly 600 species of Lepidoptera larvae.

Do you know how many species of butterfly in their larval state live on Buddleja, the famous “butterfly bush” much touted as food for butterflies, in North America? One out of the 725 species.

But wait! Of the 511 caterpillar species found on oaks in Chester Co., PA, 95% of them fall to the ground when they’re fully grown. They don’t pupate in the trees themselves, probably because they want to escape predators. Instead, they burrow into leaf litter, dig themselves into the ground, and even chew their way into rotten wood. So a stately oak in a patch of turf grass, well-mowed and sprayed, with hard-packed soil, tidied up every fall of all those rich leaves, is a desert. Put in native shrubs and/or flowers like wild ginger, foamflower, and woodland phlox. Or keep the leaf “litter.” (Change the name of litter to “natural fertilizer” and/or “habitat.”)

All data and quotations taken from Doug Tallamy’s new book, Nature’s Best Hope, to be discussed tomorrow. A book for your neighbors, I’m guessing.

Caterpillars at Backyard & Beyond.

2 Responses to “Oaks to Caterpillars to Birds”


  1. 1 Ewa Kozyra February 22, 2020 at 8:34 pm

    I have to say, this was my favorite post this year, thank you!

    I wish when replacing street trees, the city wouldn’t want to plant the neighborhood with ginkgos, but for some obscure reason it seems to be the tree of choice in our area


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