Creating a Bird-Friendly Yard
New research shows that small habitats can add up to a big difference.
On the properties most closely resembling the arid desert surroundings, she found Gila woodpeckers nesting in saguaro cactuses, Anna's hummingbirds sipping nectar from mesquite, and curve-billed thrashers nesting in cholla cactuses. She also discovered that the birds frequenting those xeriscaped properties were staying longer and eating until they were full. "They didn't have to keep moving around, which takes a lot of energy," she says. "They could stay in one patch and do all of their activities. If you're a bird that doesn't have to fly from yard to yard desperately trying to find food, you can go off and do other important things, like attracting a mate or feeding your young."
Lerman worries about one potential hazard of creating a bird retreat in a desert of grass and pavement. In the right set of circumstances it could become a Bates Motel. "We have to be really careful that when we do create these habitats we don't create ecological traps." (This refers to the inadvertent bait and switch that can happen when wildlife is drawn to an area that ultimately jeopardizes its safety.) "If you create a wildlife habitat, and then you have a cat outside, it's completely unproductive. You're attracting all these birds to your yard with beautiful plants, and your cat is waiting to kill them."
It doesn't have to be your cat either. It could be a neighbor's or a feral one. In fact, a recent study by scientists at the Smithsonian Conservation Biology Institute reported that between 1.4 billion and 3.7 billion birds are killed each year by cats roaming outdoors. "This is a huge and complicated issue," Lerman says, "because you can't control other people's behavior."
While cutting-edge research is expanding scientists' understanding of how people can support birds and other wildlife--one garden, schoolyard, and urban park at a time--there is still a lot to learn. "Prior to this research, it was largely suspected that backyard habitats could be helpful in providing sanctuary to birds during nesting and migration," says Steve Kress, Audubon's vice president for bird conservation and author of The Audubon Society Guide to Attracting Birds. "Their research gives us solid information that shows how important the native plants are."
But he emphasizes that selecting plants that host the insects birds eat is only part of the equation. Fruiting plants and seeds fuel birds during migration, and are thus equally essential in any habitat. "Of course, plants should also be selected for other features than food, such as shelter during extreme weather and usefulness for nesting structure. Just as some plants sustain diverse caterpillar populations, others provide good options for nesting structure and safety from predators."
Nest boxes hung on posts or standing trees are another key feature, he says, because people tend to remove downed trees and other structures with cavities that birds would use naturally. In addition, birds need sitting perches where they can keep an eye out for predators; a place to get out of the sun on a hot day or to weather a winter storm; water for drinking and bathing; and even some thorny shrubs like hawthorns that can provide a fortress against prowling animals, including cats.
At the same time scientists are taking a hard look at nonnative invasive species that provide birds with food but also harm the ecosystem. Porcelainberry is firmly on the National Park Service's "least wanted list" for its habit of forcefully twining through woodlands and smothering native plants. But apparently the birds aren't too picky. "[They] eat porcelainberries up the wazoo," says Michelle Frankel, a conservation biologist who is leading Audubon's Bird-Friendly Communities initiative in the Atlantic Flyway. Some people think: Why make such a fuss. Just leave it. But Frankel says you have to also consider the plants that porcelainberry displaces. What's more, not all plants are created equal. A recent study revealed that the highest fat content and energy densities in fruits that migrant birds ate at two field sites in Rochester, New York, came from native shrubs--not the aliens. The birds were choosing the higher-octane fuel and eating it more voraciously.
More and more, citizen science projects continue to deepen our understanding. Two such programs were launched this spring. "These initiatives are designed to look more closely at bird and plant associations and answer some of the questions, particularly having to do with backyard habitats," says Frankel.
YardMap is a Cornell Laboratory of Ornithology project that encourages people to gather data about the habitats that they are most familiar with--their yard, their favorite birding spot, a schoolyard, even a cemetery--to provide insights about how they can aid wildlife. The program is like Google Earth, allowing users to zoom in on their place and mark the types of plants that exist there. "It's connected to eBird [a real-time online checklist program that collects and broadcasts bird data], so they can also keep track of the birds they see," says Frankel. "It's a very cool tool."