Voices of the Forest

Black-throated blue warblers rely on a dense understory of shrubs within mature forest to successfully nest. Photo: Emmanuel Soza Foias.

It’s a blustery day in April, and you’re a bird high above the Connecticut River. Perhaps you’re a great blue heron, and since the first warm wind hit the salt marshes of Long Island Sound you’ve been following the retreating ice upriver to your wetland rookery. Or maybe you’re a hermit thrush, newly returned from a fruit-filled Rhode Island thicket to cast your flutelike song into the hemlocks of Southern Vermont. You might even be a broad-winged hawk, nearing the end of a much longer journey that began crossing the Panama Canal and will soon end in a Northeast Kingdom maple sugarbush. All of these journeys are knit by the common thread of the Connecticut River: it is both a stark visual cue for navigation and an artery of critical habitat for rest and refueling en route to breeding grounds.

Bird enthusiasts have long appreciated the Connecticut River Valley’s value as a migratory corridor. Tens of millions of birds use it annually, often in such high densities that they appear in flight on weather radar. The unique value to migrant birds is how it connects spring staging grounds along the coast to the vast tracts of temperate and boreal forest in northern New England and Canada—a.k.a., the “fledgling factory” of Eastern North America. Riparian buffers, tributary mouths, and forest patches within the valley are the rest stops along this river highway, and thus where birdwatchers are likely to encounter the greatest diversity of species in spring and fall (See “Perspectives on Wildlife” in this issue). But this region does not only provide habitat during migration. In fact, a less-celebrated but equally valuable feature of the valley is its role as breeding habitat all its own.

In 2016 the North Atlantic Landscape Conservation Cooperative—a partnership of nonprofits, natural resource agencies, and academic institutions around the Connecticut River—published a report on the status of existing wildlife habitat within the watershed and laid out a conservation design for its future. The report, Connect the Connecticut, highlighted the importance of the watershed’s forests to birds and other wildlife populations in the Northeast as a whole. Positioned between major contiguous blocks of forest in the Berkshires, Green Mountains, and northern White Mountains, the Connecticut River Valley links wildlife populations that might otherwise be separated within these core mountainous areas. This helps keep small populations of mountain species from becoming isolated and makes room for species with wide home ranges, such as large mammals, to safely disperse across the landscape.

The Connecticut River Valley is 80 percent forested, and forests of all types and ages have roles to play. Two measures, however, are particularly important when considering the significance of a patch of forest: size and connectivity. Large patches contain more interior forest, which is generally a safer place for forest-nesting bird species to raise their young. Forest edges, especially within a mixed landscape of forests, fields, and development, are often where nest predators and parasites congregate, so many forest birds may avoid smaller patches where the edge is nearer. With this in mind, landscape-scale conservation planning like Connect the Connecticut prioritizes building large core areas of forest.

The next step is ensuring wildlife can reach them, and here is where connectivity comes in. Conserving linkages between core forest blocks provides travel corridors for wildlife to safely move and disperse. In a region like the Connecticut River Valley, where a majority of land is privately owned, individual landowners have the potential to play an outsized role in supporting wildlife movement. This is true even if your land isn’t part of a large core block of forest: riparian buffers, hedgerows, and patches of native shrubs can all function as corridors for breeding and migrating birds, along with a host of other wildlife.

Ensuring the healthy function and connectivity of our forests as breeding bird habitat has never been more important. In 2019 scientists at the Cornell Lab of Ornithology, armed with decades of community science data from eBird and the Breeding Bird Survey, found that within the past 50 years North America had lost nearly 3 billion individual birds. Among these unfathomable losses were eastern forest birds, with songbirds particularly hard-hit. The wood thrush, once a common denizen of hardwood stands and river bottoms throughout the Connecticut River watershed, has declined precipitously across its breeding range. Connect the Connecticut identified this as the key representative species of mature deciduous forest. In other words, the loss of wood thrushes may say something about the health of the watershed’s forests, too.

A Bird-Friendly Maple sugarbush in Northern VT. Sugarmakers in Audubon Vermont’s Bird-Friendly Maple Program manage their woods
to include a diversity of tree ages, dense understory shrubs, and abundant dead wood. Photo: Fen Levy-O’Malley, Audubon Vermont.

The causes of continent-scale bird declines are multifaceted, and in some cases beyond the scope of the region where birds breed. For instance, habitat degradation on migratory stopover sites and wintering grounds can be especially consequential for long-distance migrants, a group that includes the majority of our forest songbird species. However, change in habitat availability or quality on the breeding grounds has been one of the most widely identified drivers of decline across North America’s forest birds. This can look like conversion of forest to other uses, such as agricultural fields or development, but might also occur through existing forest becoming less “bird-friendly” or losing particular features that breeding birds seek out and need.

Within the Northeast’s “fledgling factory,” we still have immense opportunity to contribute to reversing bird declines by addressing both issues. To tackle the first, we can continue to apply lessons such as those already in motion thanks to Connect the Connecticut: identifying core forest blocks and the corridors that connect them and ensuring they are stewarded and protected. But tackling the second issue requires creativity and readiness to adapt how we think about forests. In this way, we need to be able to think like a bird.

Beneath a forest canopy, there are a myriad of puzzle pieces that make up a suitable bird habitat, and the pieces will differ for each species. Some birds may prioritize different tree species for foraging, as each supports a different community of insects. Others may forage or nest at varying heights within the forest canopy, so providing a variety of structural components—seedlings and saplings, dense patches of woody shrubs, leafy boughs in the midstory—improves the menu options available to these birds. Standing dead wood, though not always the most aesthetically appealing, plays an invaluable role in forest ecosystems as a buffet of insect food, a safe nesting site for numerous bird species, and a source of roost cavities for winter songbirds, owls, bats, and climbing mammals. Over time, standing snags become logs on the forest floor, passing on the same benefits to the ground-dwelling community of birds and other wildlife.

Shrubland patch within contiguous forest, Southern VT. Promoting unusual habitat types within a
broader landscape context can boost local biodiversity. Photo: Fen Levy-O’Malley, Audubon Vermont.

New England’s land-use history has created a distinct lack of many of these features. Aggressive clearing following colonization eliminated the vast majority of the original old growth forest from the landscape. Then, as farms were rapidly abandoned for more productive land further west around the turn of the 20th century, forests reclaimed the land. The result today is a heavily forested landscape, but one where many forests are relatively uniform, with a single older age class in the canopy and limited structural complexity beneath. These forests still provide habitat for some bird species but lack many of the features that would support a truly diverse, resilient bird community.

Fortunately, forest stewardship can help address some of these challenges, creating habitat conditions that support a greater diversity of birds. One particular example within New England’s land-use history is maple syrup and sugar production. Even during the height of land clearing, the sweet temptation of maple sugar meant that some small parcels of original forest were maintained on the landscape as working sugarbush, the colloquial name for the forest where maple sap is harvested. However, centuries of management tradition have left many sugarbushes lacking in species diversity and complex structure, as sugarmakers cut out other trees in favor of sugar maple and cleared the understory to make room for bucket-haulers and draft horses.

Though much has changed in how maple sap is harvested, management traditions persist across the sugar maple’s range. The silver lining is that this means working sugarbush is an area with a lot of room to grow in how we manage habitat for complexity to provide for birds. Towards this aim, in 2014 Audubon Vermont formed a partnership with the Vermont Maple Sugarmakers’ Association and Vermont Department of Forests, Parks, and Recreation to develop recommendations for managing bird habitat in the sugarbush. The result was the Bird-Friendly Maple Program, a free-to-enroll conservation initiative that provides management recommendations to maple producers for enhancing bird habitat. Participating producers are then recognized and promoted by Audubon for their efforts.

Since the program’s founding cohort of five Vermont producers, it has grown to include nearly 100 sugarbushes within Vermont and expanded to six more states, with producers the length of the Connecticut River Valley in Eastern Vermont, Connecticut, and Massachusetts. Collectively, these sugarmakers steward nearly 20,000 acres of mature forestland through intentional forest management.

Spring beauties in the Upper Valley, Caledonia County, VT. Abundant populations of spring ephemerals can be an indicator of healthy soil and leaf litter, both important components of an Audubon Vermont “Bird-Friendly” forest. Photo: Fen Levy-O’Malley, Audubon Vermont.

Depending on the current state of a given sugarbush, management can look a variety of ways. Sugarbushes with existing diversity in composition and structure might require a relatively light touch in the near term, while some may lack specific features that could be selectively recruited. For instance, a forester could promote standing deadwood by girdling certain trees, or create canopy gaps that mimic the natural disturbance of a windblown tree to promote dense regeneration into the understory. These management strategies are not just important for creating bird habitat, they also promote forest health and resilience in the face of threats like climate change and invasive species. For these reasons, Audubon utilizes similar recommendations for landowners stewarding the many other types of forest in the Northeast.

Thinking like a bird also means thinking at a landscape-scale; specifically, envisioning a given parcel of land in the broader context of what’s around it. This might reveal the value of what’s already there. A patch of older forest (a conservation priority within the Connecticut River Valley) surrounded by otherwise even-aged upland forest, for example, could have magnified importance for the species that live there. Many sensitive habitat types, such as forested wetlands, may have additional special considerations at a state level that enhance their protection.

In cases where a parcel exists within a landscape of broadly similar structure, there can be major benefits to creating something new. For instance, some Bird-Friendly Maple sugarmakers have created larger gaps in their forest in the manner of a winter storm event. As the forest recovers over the decades following this type of disturbance, a rotating cast of plant species moves in, creating a dynamic patch of early-successional forest, another conservation priority within the Connecticut River Valley. One such patch at Upper Valley Land Trust’s (UVLT’s) Cream Street Conservation Area currently supports a dense stand of regenerating hardwood trees, along with thick brambles and abundant herbaceous plants. This past April, the thicket reverberated with grouse drums and waited eagerly for the promise of May’s cheerful songbird community of white-throated sparrows, veeries, least flycatchers, and chestnut-sided and mourning warblers.

Taken together, the variety and context-specificity of options at our disposal can feel overwhelming. For this reason, it’s perhaps most important to remember that conservation is a collective project and that we are also surrounded by a diverse ecosystem of foresters, ecologists, land managers, and landowner peers upon which we can rely for support and guidance. Think like a bird, yes, but don’t think alone!

The Connecticut River Watershed Partnership (CRWP) draws a community of conservation organizations towards landscape-level planning, so the priorities developed here can be invaluable for informing what to do at smaller scales. Bird-Friendly Maple producers and land trusts like UVLT actively steward hundreds of forestland properties, offering closer connection points for landowners looking for inspiration. Audubon Vermont and Audubon Connecticut offer a Forester Training and Endorsement program, where foresters are trained to create management plans that specifically prioritize bird and wildlife habitat. Peer-to-peer communities like the Coverts network, a group of nonprofits that connect landowners and natural resource professionals, allow landowners of all experience levels to share successes and learn from each others’ work.

Blowdown in mature mixed-wood forest, Grafton County, NH. Natural disturbances like these are an integral part of the life cycle of northeastern forests, kick-starting tree regeneration. Bird-friendly forest managers can mimic blowdowns by creating canopy gaps through mechanical means. Photo: Fen Levy-O’Malley, Audubon Vermont.

As autumn approaches, the eager migrants of spring are confronted with a familiar feeling of restlessness and will soon begin their return journeys down the Connecticut River Valley. As they fly, they keep in constant communication with their neighbors in the air, maintaining contact for their collective safety. Nocturnal flight calls are much shorter and softer than the exuberant songs of spring, only audible to human ears on a clear night from a high vantage point, where the river of movement passes close overhead. Yet they still may contain a wealth of information: who’s leading the charge, where they’re flying in the air column, what species are their neighbors. The meaning of bird calls can be difficult to decipher, so we might even wish to imagine more complex messages such as lessons learned from a difficult nesting season, treasured locations of venerable old forest, plans for next year. While we can’t know everything they’re saying, there is still much we can learn from birds’ capacity for resilience, cross-species communication, and perseverance. For the good of the birds, our shared forests, and ourselves, let’s follow their example.

Fen Levy-O’Malley (they/she) is a Forest Conservation Senior Associate at Audubon Vermont primarily conducting forest assessments, engaging with producers, and surveying breeding birds as part of the Bird-Friendly Maple Program.