Taking in the beautiful purple blossoms as the scent of lilac floats on the air seems like a pretty idyllic backyard setting, but new research shows that not all plants are equal. That pretty lilac, porcelain berry, fragrant bush honeysuckle, and ruby red Japanese maple in your yard might look nice, but non-native plants like these consistently have fewer caterpillars than native plants, according to new research published in July in Biological Conservation. And that means less food for birds.
And while fewer insects may seem like a good thing to some, Desiree Narango, a graduate student at the University of Delaware and lead author of the study, found that where there are more non-native plants, one of our common backyard birds, the Carolina Chickadee, stays away. Non-native plants don’t have enough caterpillars, the chickadee’s primary source of food during the summer months, to feed them.
Narango and colleagues from the University of Delaware and the Smithsonian Migratory Bird Center studied Carolina Chickadee foraging behavior, monitored chickadee nest success, and counted caterpillars in the backyards of homeowners in the Washington, D.C., metropolitan area participating in Neighborhood Nestwatch during the summer months in 2013 and 2014.
Their research also showed that Carolina Chickadees raise more baby chickadees in yards with lots of native plants. But in yards with more non-native plants, the chickadees didn’t fare so well. In yards mostly consisting of non-native plants, baby birds didn’t survive because there wasn’t enough for them to eat.
“The plants that you put in your property matter and they are not all the same,” says Tallamy, an entomologist at the University of Delaware and coauthor of the research.
“Native oaks, elms, and cherries are phenomenal food producers for birds,” says Narango. But some native plants are better than others. Tulip trees for example, are native, but researchers found that they support about 8 caterpillar species whereas an oak tree can support over 530 different species of caterpillars. If you were a bird, where would you go to get your next meal?
Urban and suburban habitats are increasing around the globe, but that doesn’t mean they can’t also provide homes for wildlife. In fact, Tallamy, says, “Now more than ever we need to create functional ecosystems in our neighborhood. It’s no longer an option.”
Tips for Turning Your Yard Into a Native Haven
What can you do to create better habitat for wildlife in your yard? Tallamy says “Cut your lawn in half, pull out the non-native species, and don’t buy new ones.”
But don’t worry, says Rhiannon Crain, “You don’t have to get rid of all your lawn.” Crain was the project leader for Habitat Network, a joint citizen-science project of the Cornell Lab of Ornithology and Nature Conservancy that ran through 2018.
“If your kids play on the lawn you should keep that lawn,” says Crain. “Focus on the spaces that you are just keeping as lawn that no one uses. If no one walks there, no one plays baseball on that lawn, consider taking that part and turning it into something else, something more useful.”
Tallamy suggests that homeowners can start by looking at the kinds of trees on their property, the kinds of trees on their neighbor’s property, and then filling in the blanks with other native plants that support a lot of insects or provide fruit. But Tallamy also suggests making a three-dimensional landscape that also includes shrubs and wildflowers.
What should you plant? Narango suggests choosing native species such as oaks, elms, and cherries. “If your local nursery doesn’t carry the plants you want, demand that they carry them,” Narango says. If you have the option between buying a cultivar or a pure native, go native, she says. Japanese cherry is a popular tree in the Washington, D.C., area, but Narango found that those trees supported fewer insects than a native cherry—only 40% as many, on average.
If you don’t have much time or are renting a property, but still want to help birds and other wildlife in your area, Narango suggests calling your local forester or arborist and telling them what species you’d like to see planted along your street or in your neighborhood. Every little bit can help, says Narango, “even a handful of native trees can function as a really important food hub for breeding and migratory birds.”
Crain also suggests that doing nothing, in some cases, can help out birds, too.
“A little thing like leaving a dead tree standing, if it’s not threatening your house, can help wildlife,” she says, noting that dead trees offer great feeding and nesting habitat for woodpeckers and other insect-eating birds.
And even if you aren’t a fan of bugs and worry that those native plants could support more insects that make your skin crawl, or itch—again the scientists say, ‘Don’t worry.’
“It’s a win-win situation,” says Narango. “The more insects you have the less you actually see them, because the birds are eating them. And besides, according to Narango, “gardening for wildlife is really the easiest kind of gardening there is.”
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