Reprinted from Mongabay on a CC 4.0. License. Original writing by Nina Foster.

As the sun rises, the ethereal song of a wood thrush echoes through Bourdon Maple Farm's 55-hectare (135-acre) forest in Woodstock. A bright scarlet tanager wings about the canopy as hungry yellow-bellied sapsuckers drill into tree bark.

At the height of maple sugaring season, birds provide a comforting soundtrack for the farm's head of operations, sales, and marketing, Meg Emmons.

"A lot of times, the birds are my only company out here in the woods," she said, smiling at a nearby black-capped chickadee. But the forest's most vocal residents are also some of its most vulnerable.

Forest birds thrive in diverse habitats that consist of young, middle-aged, and old-growth trees. Most trees in New England, however, are uniformly middle-aged after regrowth following widespread clearing for agriculture in the 1800s. Modern development pressure continues to convert woodlands into residential areas, parking lots, and other unforested landscapes, further reducing the amount of habitat available.

As a result, many forest bird populations have plummeted. Wood thrush populations, for instance, more than halved in 50 years due to forest loss that increased nest exposure to predators and parasites. Vermont's Wildlife Action Plan identifies it as a high-priority "species of greatest conservation need."

Recent technological advances have resulted in an explosion of the maple syrup industry over the past 15 years in the United States and Canada. But with the growth of production comes the temptation to favor sugar maple (Acer saccharum) trees at the expense of other tree species in the "sugarbush," as a stand of tapped sugar maples is called.

Some maple producers operate with an "I tend to the trees I tap" mentality, prioritizing maples and minimizing competition among maple trees and other vegetation. But removing too many non-maple trees puts the health of the entire forest, and hence the sugar maples themselves, at risk. In extreme cases, producers remove all non-maples growing beneath the forest canopy.

The eponymous owner of Bourdon Maple Farm, Don Bourdon, once met a producer who regularly cleared his woods with a lawn mower, cutting any species seemingly getting in the way of his maples' success. But when maples surpass 90% of the sugarbush composition, producers have effectively created a monoculture, experts say.

Calling a sugarbush a monoculture may sound strange, as the term is usually reserved for industrial agriculture, such as giant fields of corn, soy or wheat that now occupy what used to be diversified forests or prairies. By comparison, monocultures in the maple industry are less common and less harmful — sugarbushes tend to keep the forest intact, which is far better than clearing it to plant annual crops — but growing trees in a monoculture still limits the forest's ability to support wildlife and withstand ecological disturbances.

Encouraging a diversity of species in tended fields or forests is a major tenet of agroecology, which treats agriculture more like a functioning ecosystem than a food factory. Encompassing an array of techniques from organic farming to integrated pest management and agroforestry, agroecology is also a top climate solution since it sequesters carbon from the atmosphere, as the Intergovernmental Panel on Climate Change stated in 2022.

Along with a decline in crop or tree diversity, the diversity and abundance of birds decrease when, as in the case of maple monocultures, sugar maple trees exceed 75% of a forest. So, the conservation nonprofit Audubon Vermont focused on developing a solution and worked with the Vermont Maple Sugar Makers' Association and the Vermont Department of Forests, Parks and Recreation to launch the Bird-Friendly Maple Project in 2014. The program celebrates producers who safeguard and enhance forest bird habitats and provides a label that customers can look for when buying syrup.

For a maple producer to earn the bird-friendly label, they must commit to a management plan that ensures a future sugarbush composition of no more than 75% sugar maples. In addition to enriching tree species diversity, bird-friendly producers must improve the structural complexity of their sugarbush with management objectives that aim to have vegetation covering at least 25% of the forest's understory (the zone comprising the first 5 feet above the forest floor, where flowers, ferns, and shrubs are likely to grow) and its midstory (trees and shrubs standing between 5 and 30 feet in height). Eventually, participating farms' sugarbushes should look like a wall of green in summer, with vegetation providing optimal nesting and foraging opportunities from the ground to the forest canopy.

"A messy forest is a little harder to work in. As a sugar maker, it can be difficult to walk out and tap your trees if you're working through brambles and snags — but it's good for the wildlife," said Aaron Wightman, lifelong maple producer and co-director of the Cornell Maple Program, where researchers also explore additional sugarbush diversification efforts such as growing nutrient-rich forest products like berries and nuts under the forest canopy, and the harvesting of alternative tree syrups. "Retaining at least 25% non-maple species and creating structural diversity in a sugarbush are powerful strategies for bolstering the populations of birds and other forest species," Wightman told Mongabay.

With diversity comes resilience. In addition to better supporting wildlife, a bird-friendly forest is less susceptible to threats including pests, disease and extreme weather events, owing to a diverse community of trees and because birds are voracious predators that eat many bugs that may damage trees or spread tree diseases.

Audubon Vermont conservation biologist Steve Hagenbuch compares diversifying a sugarbush to navigating the stock market. "If you put all of your funds in one account, and something bad happens to that account, you're in trouble. But if you diversify your portfolio and you have it spread out, then you can handle something negative hitting one part of your investment," he said.

In August, Audubon Vermont, along with the Vermont Center for Ecostudies and the University of Vermont (UVM), wrapped up a study launched in 2020 to quantify how forest bird communities respond to different habitat characteristics in actively managed sugarbushes. The data will be used to update and refine the Bird-Friendly Maple Project's sugarbush management guidelines.

Preliminary results gathered in 2020 and 2021 from field surveys of breeding birds, foliage- and litter-dwelling arthropods, and vegetation across 14 active sugarbushes in Vermont—nine of which were enrolled in the Bird-Friendly Maple Project—suggest that the program's current management guidelines need little modification. Cultivating diverse vegetation and structure in a sugarbush allows the landscape to better meet the needs of a wider range of forest birds, supporting bird diversity and abundance. For example, increases in low woody vegetation and sapling richness were linked to a significant increase in the abundance of three species that prefer to nest in saplings and shrubs: mourning warblers (Geothlypis philadelphia), chestnut-sided warblers (Setophaga pensylvanica) and black-throated blue warblers (Setophaga caerulescens).

Leaf litter depth proved to be one of a few especially important habitat features that benefit all forest birds. Many bird species rely on this rich carpet of organic material, whether for searching out insects and seeds, snagging twigs and leaves to build nests or camouflaging themselves among the debris to avoid nearby predators. Nonnative earthworms, however, can deplete this valuable leaf litter layer. Audubon Vermont will likely incorporate additional requirements into their bird-friendly management guidelines based on the study's findings, such as paying attention to the presence and distribution of earthworms in the sugarbush.

UVM researchers gathered additional field data in 2022 and 2023 and continue to build upon the study's evaluation of bird-friendly management practices. Liza Morse, a UVM Ph.D. candidate whose dissertation investigates the link between maple sugaring and sugarbush biodiversity and resilience, assisted with all four years of data collection and plans to interview participating sugar makers about their specific management approaches.

"Current bird-friendly targets are based on best practices for forest management in general, but the hope is that we can drill down on the drivers of change in a sugarbush and what they mean for birds," Morse said. "Programs like the Bird-Friendly Maple Project are only going to improve as they are evaluated by research and continue to self-reflect."

Bourdon Maple Farm's Meg Emmons first reached out to Hagenbuch in late 2021 when she noticed the Bird-Friendly Maple Project logo on other producers' websites. After conducting a thorough analysis of their 10,000-tap operation the following spring, Hagenbuch concluded that to be recognized by the program, they simply needed to add a bird-friendly focus to the forest management plan they had already been following for four decades.

Their forest is a work in progress — sugar maples still account for about 90% of the larger trees in the sugarbush — but their commitment to diversification earned their bird-friendly title. After all, maple producers work in "forest time," meaning it takes years, even decades, to achieve change.

Emmons and Bourdon support birds and the rest of their forest ecosystem by thinning sugar maple density in their woods, fighting invasive plants like honeysuckle to encourage growth of native species, and leaving dead trees on the ground or standing upright for hole-nesting birds like woodpeckers to use. Between May and mid-July, they avoid thinning trees and other practices that could disturb birds during their nesting season.

While walking through the sugarbush, Emmons spotted a long, thick tree branch that had fallen on some tapping equipment. "We'll leave that for the birds," she said as she tossed it aside.

Mr. Bourdon is just one of 90 Vermont maple producers who enthusiastically joined the Bird-Friendly Maple Project, which is now being replicated in New York, Massachusetts, and Maine. Across all participating sugarbushes, there are now approximately 7,284 hectares (18,000 acres) of forest managed with birds in mind, thanks to the program.

And birds aren't the only winners. Bird-friendly producers can brand their products with the program's label showcasing the scarlet tanager (Piranga olivacea), a species that's one of the effort's big beneficiaries. This attractive logo is a visual recognition of their sustainable maple operations and attracts new customers and business opportunities.

For Bourdon and Emmons, the label presents an exciting opportunity to keep up with the resurgence of interest in local, sustainable food products and to educate their customers about conservation efforts in maple production. On sugarbush tours, they distribute a maple bingo game with a prompt that encourages kids (and adults) to look and listen for birds. Emmons has met birders who are thrilled to learn that maple syrup producers like them are playing an active role in supporting wild bird populations.

"People really value it," said Emmons. "They're supporting environmentally friendly products and causes through socially conscious shopping."

Bourdon summed up the value and necessity of harvesting products from healthy forest ecosystems in one simple phrase.

"Although boiling happens in the sugarhouse, maple syrup is really made in the woods."

SHARE This Sweet Conservation Action With Your Friends…