Landscaping for the Birds, the Bees and the Bugs
“How about a little Joe-pye weed? They’ll give you some color, purple flowers in late summer. Butterflies love them,” Elmer Dengler suggested. Bowie City Green Team member Dengler was dispensing advice to a customer at the Bowie-Crofton Garden Club’s 30th annual native plants sale, one of the ways the team promotes its mission of Bringing Back Birds and Butterflies.
In a public lecture the night before, researchers Desiree Narango and Dr. Dara Satterfield had reported years-long research on how birds and insects, including butterflies, benefit from native plants and how even our small yards and gardens can create and restore healthy ecosystems, becoming refuges of biodiversity. Narango works with the University of Delaware’s well-known Entomology and Wildlife Ecology professor Doug Tallamy as well as the Smithsonian Migratory Bird Center. Satterfield works with the Smithsonian Migratory Bird Center, too, focusing on migratory insects.
From 2013 to 2016, Narango’s research took her to more than 200 metropolitan D.C. area homeowners’ yards, her study sites, including neighborhoods in Bowie, Annapolis, Crownsville and Millersville. She followed color-banded Carolina chickadees to document what they feed their young in the April-to-June breeding season and where they find food.
Chickadees enjoy sunflower seeds at bird feeders, but their broods require more high-protein diets. The larvae of moths and butterflies make perfect meals. For the 16 days between hatching and fledging, a clutch of five chickadee chicks will consume thousands of caterpillars found and delivered by their hard-working parents.
Those caterpillars are themselves picky eaters, known as specialists. And that’s a problem, Narango explained.
In Maryland, 30 percent of native caterpillars rely on one kind of native plant. Nearly 90 percent eat only five or fewer native plant types. For example, the monarch butterfly in the caterpillar stage feeds solely on milkweed.
Without those plants in the landscape, those specialist insects and caterpillars won’t be around. That means chickadees, for example, will have to spend more time hunting caterpillar prey farther away from their nest sites, or eat insects of lower nutritional quality.
Late last year Narango published her findings in the journal Biological Conservation. Chickadees in her neighborhood study sites, she found, preferred to forage on native plants because, as this scientist says, “those plants have much more bug food.”
Native oaks, which include Maryland’s state tree the white oak, host more than 500 different species of caterpillars. That’s at least one-fifth of the estimated 2,478 caterpillar species documented in Maryland. Native cherry, elm, hickory, willow and birch trees are also good caterpillar plants. By comparison, non-native gingko trees support only six caterpillar species, bamboo just one and many non-natives none.
Many different migratory birds also use neighborhoods as stopover or nesting sites. Predominantly insect-eaters, birds such as warblers and orioles need ready food supplies. A significant number will make long journeys to breeding grounds up north. One native oak can be a refuge for these birds in an otherwise built-up and paved-over environment.
Migratory insects, including monarch butterflies, are Dara Satterfield’s subjects. The monarch population that breeds here in the Chesapeake region and other parts of eastern North America overwinters in just over a dozen mountain forests of Oyamel firs in Central Mexico. Butterfly counts in Mexico report a shocking 80 percent drop since the 1970s. Habitat loss in both the U.S. and Mexico is a major culprit.
Despite studies showing worldwide insect declines over the past 20 years, including one documenting a 75 percent decrease in Germany, Satterfield remains hopeful. “Once native insects have the right plants and conditions, they can rebound quickly,” she says. For monarchs in the Bay area this spring, the right plants are native nectar plants, most of which are perennials: bee balm, aster, cardinal flower, black-eyed Susan, goldenrod, Joe-pye weed and more.
The message is clear, says Chris Eberly, director of the Maryland Bird Conservation Partnership. “Bird and insect recovery info is out there now. It’s simple. Plant native plants and trees. They attract the most insects, especially caterpillars that breeding birds need. We can all do this.”