More than maple: How sugarbush structure supports forest birds

The U.S. bird population has been declining by the millions for several decades. Thankfully, there is a growing interest in managing sugarbushes as an ecological support for our diverse bird populations.

Steve Hagenbuch, the lead on the national Audubon Bird-Friendly Maple program, shared ideas of how maple producers can support their local bird populations in a recent webinar.

Hagenbuch explained that most maple syrup production coincides with core breeding habitats for dozens of forest bird species, especially forests in high maple-yielding states like Vermont, New York, Maine, Wisconsin, Pennsylvania, Ohio, Massachusetts, Minnesota, Indiana, Connecticut, Michigan and West Virginia. When you overlay a map of the highest maple producing regions of the Northeast and a breeding ground concentration map of 72 species of forest birds, they are almost an exact match.

Sadly, the U.S. has lost a staggering 2.9 billion birds since 1970 – 170 million birds fewer in our eastern forests alone. The entire forest bird population is replaced every few years in these forests. To “Protect birds and the places they need, today and tomorrow” is the mission of the Audubon Society. With a little wisdom from Audubon, sugarbushes can be managed in ways that set birds up for success.

Sugarbushes (and forests in general) have three distinct layers: the forest floor (ground level to six feet), the understory or middlestory (six to 30 feet) and the canopy (higher than 30 feet). Different species of birds rely on all three layers for survival and it’s important for producers to understand all three and why best management practices are important. Hagenbuch used nesting and foraging profiles of four species to illustrate this point:

• The program’s mascot, the scarlet tanager, prefers to nest high in the canopy in maple, beech, oak and hemlock trees. They love to eat the sorts of bugs that congregate around yellow birch but largely avoid sugar maple and beech trees for foraging.
• The black-throated blue warbler has nests concealed by vegetation about three to five feet above the ground in saplings and shrubs like hobblebush, rhododendron and spruce. They forage for insects and spiders in the same undergrowth, especially on the underside of vegetation.
• The wood thrush nests from 10 to 20 feet above the ground in the middlestory, where a fork of a branch will give good support and provide cover. But they forage for invertebrates in leaf litter and on the ground as well as for berries and black cherries.
• Yellow-bellied sapsuckers excavate dead or rotting trees to build their nests. Making little holes called wells in the sides of trees, they literally suck sap and eat the bugs that come for their leftovers as well as ants, spiders and bugs that hide under tree bark.

It’s almost as if every part of the forest has a bird that relies on it for survival – hence the program’s “more than maple” emphasis on species diversity in the sugarbush.

Hagenbuch summarized the program’s goals as education, technical assistance and producer recognition:

• Educate maple producers and consumers on the importance of healthy forests to birds and how they can be partners in conservation efforts.
• Provide technical assistance to maple producers on managing sugarbushes with birds in mind.
• Recognize maple producers for their efforts to incorporate bird habitat into their forest management.

Sometimes humans get a little too neat in the sugarbush and make them look like parks. It’s aesthetically pleasing and it makes us feel like we are restoring order, but is it in the best interest of our local bird population? Not at all.

Common birds like the wood thrush have lost six out of 10 members due to habitat changes largely caused by humans, creating a downward curve in population. One of Audubon’s central questions is how they can help “rebend the bird curve.”

Bird‑friendly management focuses on structure, diversity and dead wood to support the species mentioned above and more. These percentages are to be calculated by visual estimation.

• “More than maple” – More than 75% of the trees in the sugarbush can be sugar maples. Where maples are the dominant species, consider planting some diverse understory species, including berry bushes, to support different birds.
• “Layer cake” – At least 25% understory and 25% middlestory woody stemmed vegetation cover must be in place, excluding herbaceous and fern cover.
• “Dead wood is good wood” – The program requires dead tree snags, hollow logs for grouses and even dead wood on the forest floor, since rotting wood attracts insects birds like to eat. Whole tree harvesting is prohibited.

So far, the voluntary program has 149 producers and 19,700 acres of sugarbush participating across the Northeast and Midwest. You don’t need to meet all of the requirements in order to join the program. Meeting the standards is a process and Audubon will help you work through it. Producers can request habitat assessments or assistance to begin developing management plans. Many states provide funding to aid producers in the plan writing process.

The Audubon Society provides a Bird‑Friendly Maple label and associated marketing materials that help producers communicate their stewardship and draw consumers. Even if you aren’t a producer, you can still get involved by training with Audubon to become an assessor.

Our forests provide birds with homes and food sources that humans can either ruin or cultivate. Hagenbuch underscored the project’s goals with their slogan: “Healthy forest, healthy habitat.”

To start making a difference through their program, reach out to Hagenbuch at steve.hagenbuch@audubon.org or visit audubon.org/our-work/grasslands-aridlands-forests/bird-friendly-maple for more information.

by Joseph Armstrong