What if I said we should landscape for the caterpillars and then everything would be all right? I would be mocked. There would be eye rolling. My Certified Nursery & Landscape Professional (CNLP) badge would be torn from my shirt and I would be banned from Plant WNY. But actually, from a chickadee’s perspective ...
There are very important reasons to support caterpillars, especially if you like birds. Doug Tallamy, entomologist and author of the breakthrough book “Bringing Nature Home” explains that 96 percent of terrestrial birds rear their young on insects – surprising to most people who hear it. And caterpillars are the form of insects that baby birds need. A baby’s esophagus needs soft material to swallow and digest and the caterpillars provide the right proteins, lipids and carotenoids for good nutrition.
Bird parents have a tough job. It takes a lot of caterpillars to raise a family. How many? In an ongoing research study at the Smithsonian Migratory Bird Center (SMBC), doctoral student Desiree Narango has been counting. The Carolina chickadee alone (our common chickadee) requires some 5,000 or more caterpillars for a clutch of three, served during about 16 days. One pair of chickadees was observed delivering a caterpillar to the nest every three minutes, including 17 different caterpillar species. Other counts showed 400 to 570 caterpillars per day flown in for other clutches.
But what if the caterpillars are not conveniently located? The birds that work the hardest, traveling the farthest, will reproduce less successfully. Baby birds will die. Last week at the University at Buffalo’s Center for the Arts, in a program hosted by the Western New York Land Conservancy, Tallamy showed us many fine pictures of birds delivering mouthfuls of caterpillars. But we also saw a picture of dead baby birds, their stomachs filled with seeds – indigestible for the very young. We need – they need – caterpillars.
Right plants, right caterpillars
A little problem crops up when you decide to help birds by serving up caterpillars: They won’t eat just anything. Most caterpillars are very specific about the plants they can eat. Narango explained in an SMBC article that chickadees go to native trees where the caterpillars are: “If you have a lot of trees that are not native, to the birds it’s almost as if there are no trees at all.” The birds somehow understand that native insects – caterpillars – require the native plants with which they co-evolved. The most familiar example is the monarch butterfly, which – now many people do understand – must have milkweed plants as larval (caterpillar) food. But that’s true of some 90 percent of moth and butterfly caterpillars: They must have the right trees, shrubs or herbaceous plants. That means native plants and lots of them – i.e. diversity.
Birds aren’t the only ones that benefit from a caterpillar-friendly yard. Plants need caterpillars too: Nearly 90 percent of plants depend upon pollinators – and butterflies and moths (that come from caterpillars) are pollinators. Bees and pollinating wasps are also pollinators and benefit from many of the same plants. Caterpillars also feed small and large mammals, spiders, amphibians and more. Even a fox, said Tallamy, gets 24 percent of its diet from insects.
Plants that host diversity
There is plenty of evidence supporting the value of native plants for the all-important native insect population. In a straightforward test, Tallamy and his team compared two 12-by-12-foot garden plots, one planted with all native and the other with non-natives. The result was dramatic: The native plant plot continually offered up hundreds of caterpillars. The non-native plot? About two (and they were probably lost). Obviously for all the mama chickadees and other birds, small plots are not enough. But what if we plant 25 percent native plants in millions of yards in thousands of suburbs and cities? What a better bird – and human – world it could be.
Inevitably worries creep in: Joe homeowner wants a pretty, well-tended looking yard – and with caterpillars eating everything it will be a mess, won’t it? Leaves full of holes! Yucky caterpillars dropping on the picnic table– can’t be good, right? Wrong. First, look at a forest, alive with birds and caterpillars and so much other life. Plants tolerate plenty of chomping. Or look at any oak tree – the tree that hosts the most caterpillars. (Typical counts show 410 caterpillars (19 different species) on one tree, 557 caterpillars on another.) Those oaks look gorgeous. No noticeable damage. They host whole communities of living things, while providing you with shade, oxygen, carbon sequestration and cooling in summer. We have to relax our expectation that every leaf should be intact on landscape plants. See some holes? You’re doing it right.
Besides oak trees, other native plants are crucial. Tallamy compared caterpillar counts on black cherry trees (249) and native viburnums (103) with counts on a non-native callery pear (1) or a gingko (2). He also mentioned American beech, white and green ashes, junipers, willows, pines, sweetgum, and poplars as crucial players. High caterpillar numbers aren’t the only goal of course. Certain butterflies must have certain larval food plants. Spicebush swallowtail butterflies rely on the spicebush (Lindera benzoin) or sassafras tree (Sassafras albidum) for caterpillar food. Like monarch butterflies requiring native milkweeds, many threatened or endangered species need us to plant very specific species for their survival.
Many lists can help you choose native plants. Tallamy’s most recent book with Rick Darke, “The Living Landscape” (Timber Press, 2014) offers thorough lists of plants with their ecological functions (bringingnaturehome.net). Find Buffalo Niagara Riverkeeper’s terrific new Native Plant Guide for WNY (bnriverkeeper.org). The National Wildlife Federation, with U.S. Forest Service and Tallamy, will soon provide the Native Plant Finder for searching by ZIP code. Meanwhile urge our garden centers and nurseries to carry native plants – and buy some.
At UB last week Nancy Smith, executive director of the WNY Land Conservancy, said it best: “In Western New York we are poised to surge forward in our commitment to native plants.” Indeed, we are, and we must. Our ecosystems and mama chickadees are counting on us. And as Smith said, “There is no time to dilly-dally.”
Sally Cunningham is a garden writer, lecturer and consultant.