Efforts to preserve our native wildlife, whether by governmental agencies or nongovernmental organizations, have increasingly been shifting toward conserving habitat by protecting and growing native plants.
This evolution came from the growing realization that, without suitable habitat, no species could be preserved in the wild. This shift in thought was apparent in the “Habitat Conservation Forum: Practices that Sustain Virginia’s Wildlife and Native Plant Communities,” which I attended in Culpeper last month (Feb. 23).
The forum was co-sponsored by the Habitat Partners Program of the Virginia Department of Game and Inland Fisheries (VDGIF) and the Virginia Coastal Zone Management Program, Virginia Department of Environmental Quality. These two programs have allied to form the Virginia Native Plants Marketing Partnership.
The forum presentations got deep into the weeds, so to speak, of habitat conservation — from planting for pollinators to creative landscape design that focuses on native plants, to the limits of habitat restoration. It also included an update on the Virginia Wildlife Action Plan. I found the content so interesting, important and densely packed that I’m splitting my take on it into more than one column, starting with the keynote presentation, by entomology professor Doug Tallamy.
In 2007 Tallamy wrote a fascinating book, “Bringing Nature Home,” about how important suburban (“backyard”) habitat is to pollinators and other wildlife. Because we humans “are everywhere now,” he said at the forum, we need to consider the habitat within built landscapes, such as the suburbs.
His presentation, “A Chickadee’s Guide to Gardening” dug deeper into that theme, focusing on an aspect of wildlife habitat he said is often overlooked: food. The kind of food birds need changes depending on the time of year, such as when some are migrating or when birds are raising their young.
Using chickadees, Tallamy deftly tied the survival of native birds to that of native plants through their mutual link to the food web — caterpillars, which 96 percent of North American land birds raise their young on, he said. As he explained, although many birds, including chickadees, are seedeaters, the larvae (of butterflies, moths, flies and other insects) are much easier for the birds’ young to swallow. Chickadees feed their young “almost exclusively” caterpillars, which are also packed with essential nutrients, such as protein, lipids and carotenoids.
In studying Carolina chickadees, Tallamy found that, to raise a brood, they needed 6,000-9,000 caterpillars, depending on the size of the brood’s size. That means about one every three minutes until the young fledged, or, as another researcher found, about 390-570 caterpillars a day. The pair he studied brought species of 17 caterpillars to their young, and the parents go on feeding their young caterpillars even after they fledge.
Chickadees are “tiny birds,” he said, so think about how many caterpillars a pair of woodpeckers, or other large species common to backyards, would need. And to be efficient, bird parents need to hunt close to the nest.
Sadly, most yards are 90 percent grass and 10 percent trees, Tallamy said, with nonnative plants making up 80 percent of the total. He cited John Pickering, a researcher at the University of Georgia, who has estimated that “a reasonably landscaped suburban lot ought to produce over a thousand species” of caterpillars.
But not any plant will do for a particular species. Most insects have adapted over many years, even millennia, to the toxins that just one or two plant species produce to ward off insects that want to eat them.
While most nurseries and landscapers may promote plants that provide seeds and berries to birds, they don’t tend to promote plants that feed caterpillars, Tallamy said, such as oaks, which are “the most important plants we can put in our yard.” In 2014 he counted the caterpillars on a white oak in his backyard, finding a total of 410, representing 19 species. He also found 456 caterpillars on a native black cherry tree. Native trees are “foraging hubs,” he stressed — if they are taken out, bird populations will collapse.
In showing slides of landscaping in the Delaware suburb where he lives, he pointed to one nonnative tree that is ubiquitous in such developments (including here in Virginia) — the Asian Callery pear. Popular with developers, landscapers and residents of suburban tracts, they are fast-growing, uniform and tidy in shape (conical), and are covered with white blossoms in the spring.
Tallamy also counted caterpillars on a Callery pear tree and burning bush (another nonnative popular in suburban landscapes) and his examination yielded only four caterpillars in total, he said. He ran through a list of other nonnative trees and other plants, including Asian cherry trees and gingko, that are popular in the suburban landscaping but pretty much worthless to wildlife.
By planting such nonnatives, “we are creating sterile landscapes that are literally starving our birds, Tallamy said. “There’s almost nothing on these plants.”
But doesn’t the fact that we see native wildlife consuming the fruits and other products of nonnative plants, such as autumn olive, mean the wildlife are benefiting from eating them?
The short answer is “no,” according to Tallamy. Again pointing to birds, he said adult birds need certain nutrients from berries (such as fat or sugar) at particular times of the year, and the timing of the fruits produced by nonnatives generally does not match up with our native birds’ needs. Native birds will actually throw up the seeds of common buckthorn, a shrub often planted to form hedges, Tallamy noted.
Although native birds may feed on a nonnative plant, it really serves as a biological sink, distracting the birds from the native foods they need while they help the plant by dispersing its seeds in their excrement.
Native plants are special, Tallamy said, because “they’re the only ones that our native animals have adapted to.” We need to raise the bar when it comes to landscaping, he concluded, and plant — or even better, leave in place —more natives because they support life, sequester carbon, clean and manage water, enrich soil and support pollinators.
© 2016 Pam Owen
To learn more about supporting backyard wildlife
Visit the “Bringing Nature Home” website and also check out a video being produced, “Hometown Habitat,” that is based on the book, at Meadow Project website. Tallamy also wrote a second book, with co-author Rick Darke, on the backyard habitat in 2014: “The Living Landscape: Designing for Beauty and Biodiversity in the Home Garden.”