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Audubon Vermont is looking at how to improve forest bird habitat in a way that also enhances the ability of forests to adapt to climate change.

Audubon Vermont and the Vermont Department of Forests, Parks, and Recreation developed the innovative Foresters for the Birds project, which works to maintain working forests and bird habitat by integrating the practices of timber and songbird habitat management. More recently, Audubon Vermont has been looking at how its efforts to promote "Silviculture with Birds in Mind" can also help forests adapt to changing conditions.

Project Area

Northern hardwoods stand in the fall
Audubon Vermont is using two demonstration locations to implement practices drawn from Audubon Vermont’s "Silviculture with Birds in Mind" in a way that not only improves breeding bird habitat but also address expected climate change impacts. The demonstration locations include Vermont Land Trust's (VLT) Mud Pond Forest in Greensboro and the Cold Hollow to Canada Woodlots region which spans seven towns in northern Vermont: Fletcher, Waterville, Belvidere, Bakersfield, Enosburg, Montgomery, and Richford. These locations are representative of common northern hardwood forest conditions in Vermont and regionally, in that past management has resulted in forests that are largely young (50-80 years old), and even-aged. Throughout Vermont, these forest conditions on small parcels usually means that pre-commercial timber improvement treatments do not happen due to the costs involved; leaving large swathes of Vermont’s forest vulnerable.

Management Goals

These silvicultural treatments are aimed at enhancing species and structural diversity to affect the following near term (0-15 year) habitat and timber quality as well as and long-term (50+ year) adaptation:

  1. Maintain or improve the ability of forest to resist pests and pathogens be retaining and releasing the most vigorous trees, and developing a more complex structural and species diversity. Research has shown that maintaining biodiversity buffers against pests and pathogens. Diversity of structure and enhanced vigor also enables the forest to resist and respond to disturbances by pests and pathogens.
  2. Prevent the establishment of invasive plants with pretreatment removal and post treatment monitoring.
  3. Manage herbivory by keeping tops unlopped and retaining coarse woody material
  4. Protect forest from severe disturbance and prepare for these disturbances by enhancing residual vigor and growth using crop tree release and promoting regeneration throughout the treatment area.
  5. Maintain and enhance species and structural diversity by implementing a variety of silvicultural treatments across the harvest area and by retaining biological legacies such as large trees, hard and soft mast, cavity trees, and snags.

Climate Change Impacts

Vermont and the Atlantic Northern Forest region is considered North America’s nursery for neo-tropical migratory birds; in fact this region has some of the highest diversity of breeding birds in the United States. However, a number of studies project changes to both bird populations and forests due to climate change. The National Audubon Society’s 2019 "Survival by Degrees" report predicts that roughly half of Vermont’s birds will see their ranges shift or contract by 50% or more. Climate Change Bird Atlas results also indicate that climate change will alter breeding habitat conditions for priority bird species in Vermont and regionally. Some more specific impacts on forest birds include:
Increased winter minimum temperatures may lead to range expansion of damaging non-native insects such as hemlock wooly adelgid, resulting in decreases in native tree species diversity.
Increases in non-native invasive plant species may decrease the abundance of the high-quality food resources (i.e., insects) and increase the abundance of low-quality food resources available during the nesting season.
Increased frequency and intensity of extreme weather events may result in more young, early-successional forest habitats to become more abundant across the landscape.
Reduced habitat suitability for many common tree species is likely to result in changes to the bird species community, their nesting success, and overall incidence of birds that are currently characteristic of the region.

Challenges and Opportunities

Despite the potential impacts and challenges to forests and forest nesting birds as a result of climate change, there is a significant opportunity for bird conservation in Vermont and regionally. Northern New England is at the core breeding range many bird species. For example, the black-throated blue warbler has nearly one-third of its global breeding population in the region. Although climate change models show decreasing habitat in the southern part of its breeding range, the Northeast is likely to continue to provide suitable habitat, increasing the region’s importance to the global conservation of many bird species.

Climate change will present other challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Deer populations are low but growing in the region due to increasing winter temperatures and may add additional stress to regenerating tree species.
Warmer winter temperatures and inconsistent frozen ground make the harvest operating window shorter, with more frequent stopping and starting mid-harvest.

Opportunities

Northern New England may be partially buffered by increases in temperature and may continue to provide suitable habitat for many bird species.
Mud Pond Forest currently does not have many non-native invasive species and deer populations are low.
Dry summer conditions may provide a potential alternative window for harvest operations. If possible, operations would be done outside of the bird nesting season (May to mid-July).

Adaptation Actions

The demonstration utilizes non-commercial treatments (Cold Hollow to Canada Woodlots) and commercial  treatments (Mud Pond Forest) that will have an immediate effect of improving the overall resilience of the forest (i.e., the ability of the system to maintain its ecological state given increased disturbance and change) to changing conditions, while simultaneously beginning a longer-term transition toward future-adapted forests.  These silvicultural treatments aim to create distinctly different stand structures and shift species composition toward species that will fare better under future conditions, while serving important habitat functions. Additionally, although tree planting is a rare practice in Vermont’s forests, some sites include planting future climate-adapted tree seedlings (e.g., red oak) to facilitate the movement of more southern, native species which are likely to have suitable habitat under future climate conditions.

  • VLT's Mud Pond Forest also serves as a research demonstration site which is testing the outcomes of Resilience and Transition treatments compared to a no-management control. Experimental harvests were implemented in fall 2022- winter 2023.
  • In the Cold Hollow to Canada Woodlots region, the integration of multiple forest landowners in cross-boundary management also allows for facilitating change at the landscape-level.

Specific adaptation approaches and tactics used at the demonstration sites include:

Area/Topic
Approach
Tactics
Mud Pond Forest (Vermont Land Trust)
Conduct group selection with 1/10 to 1/4 -acre canopy gaps across 20% of the stand and thinning/crop-tree release across 80% of the stand (Resilience treatment).
Implement continuous cover irregular shelterwood with larger canopy openings (1/3 to 1/2-acre) across 20-25% of the stand (Transition treatment).
Plant climate-adapted species in gaps including bitternut hickory, red oak, basswood, American chestnut, white oak, black birch, black cherry, red spruce, and white pine (Transition treatment).
Designate a no-management area (experimental control).
Cut and leave tops and deadwood in gaps and across the slope after harvest.
Use tree tubes on a subset of planted seedlings to protect from herbivory.
Cold Hollow to Canada Woodlots
Create canopy gaps to increase regeneration of native species and increase structural diversity.
Partner with the Vermont Youth Conservation Corps forestry program to conduct timber stand improvement (e.g., crop tree release, gap formation) and invasive species control on private lands.
Underplant mast species (chestnut, oak) and shrub species that provide wildlife habitat and food sources.
Use cut-and-drop to increase the amount of downed woody material on the forest floor.
Shift to using low-impact harvesting equipment to reduce impact when harvesting on non-frozen ground.
Improve forest road infrastructure (e.g., install larger culverts) to be more resilient to flooding events.

Monitoring

The Mud Pond Forest has ongoing monitoring to test the outcomes of Resilience and Transition treatments compared to a no-management control. Items being measured include: Vegetation (overstory, understory, regeneration), deadwood, and annual breeding bird surveys (since 2012).

At the Cold Hollow Woodlots, some landowners are monitoring for presence of bird species post-treatment.

Project Videos

Next Steps

Preliminary outcomes: At Mud Pond Forest, there has been an increase in gap-foraging bird species that were targeted by the treatments (i.e., eastern wood pewee), indicating success so far for the target suite of birds species. The regeneration response was positive, however, staff learned that at other sites with less- enriched soils (i.e., Audubon Vermont's Green Mountain Audubon Center), canopy gaps for regeneration may need to be larger than the 1/10-acre gaps (aim for 1/4 to 1/2-acre), especially if deer pressure or past land use has degraded the site.

Keywords

Wildlife habitat

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