Shrubland Species

Tim Duclos, MSc. - Conservation Manager, January 2020

In the Winter issue of the Ridgeline, I reported out on our recent efforts to benefit our feathered friends through a newly forged partnership with Audubon Vermont’s Bird-Friendly Maple program. As a second component of this bird-related series, I would like to tell you about our efforts to help another cohort of birds, shrubland obligates, through recent forest management efforts.

Among bird species groups, shrubland obligates (i.e. those that depend upon young, regenerating, forests) are in rapid decline, in part because the availability of their requisite habitat is at a modern low. The natural regeneration of much of the forested landscape, post agricultural decline beginning in the 1800’s, has led to shrublands becoming a relatively rare component of the Vermont landscape. Merck Forest shares the history of this working landscape and as such, the situation is much the same here. Among the nearly 3200 acres of land managed by Merck Forest, a mere 35 acres, or about 1%, is currently classifiable as ‘shrubland’. Moreover, many of these areas are nearing, or past, the age at which prime conditions exist for these birds, based on current science supported by data from the Green Mountain National Forest (Smetzer, King, & Schlossberg, 2014).

Yet, bird surveys conducted in 2019 at Merck Forest confirm that these areas are still occupied by shrubland obligate species. Mourning warblers (Oporornis philadelphia), chestnut-sided warblers (Dendroica pensylvanica), Eastern towhees (Pipilo erythrophthalmus), common yellowthroats (Geothlypis trichas), gray catbirds (Dumetella carolinensis), ruffed grouse (Bonasa umbellus; not a songbird, but notable) and other associated species can still be heard in many of these areas, from the oldest and largest current shrubland (25 acres/12 years old patch cut) off of the Lookout trail, to some of our newest and smallest (ex: 2.5 acres/4 years old patch cut) at Viewpoint Cabin. An additional fraction of these 35 acres have been freshly cleared in the last two years and are set to soon regenerate into young forest suitable for shrubland species. The harvest off of the Silviculture trail and that completed along the southern portion of the Stone Lot road are our most recent examples. Our most ‘prime’ shrubland, in terms of current age and condition, is an 8-year-old/6.6 acre cut, running along the northern edge of the westerly portion of Stone Lot road (Image 1). This area is just beyond the eastern border of the farm and an easy walk from the visitor center, making it ideal for visitors to experience. Just look left as you follow the road and enter the woods. I have also encountered some of these species in forest gaps deep in the interior of the forest, such as those created within the Foresters for the Birds demonstration site off of the Hatch trail - although I would posit that these are more likely transient individuals and do not necessarily represent evidence of an established breeding population.

It is important to keep in mind that shrublands are temporary habitats, climaxing in suitability for obligate species, generally, around 8 years of age (Smetzer et al., 2014). Thus, they must be created at a regular frequency on the landscape in order to sustain a population of shrubland birds. This happens naturally through disturbance (wind, fire, ice, disease outbreak, etc.) or prescriptively, through forest management (i.e. a patch cut). Furthermore, there is a growing body of research capturing the relationship between size, shape, and assembly of these habitats to occupancy, abundance, and species composition (Roberts & King, 2017). As applied ecologists, we use this body of knowledge as a means to optimally design and prescribe the creation of these habitats in place of natural disturbance.

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With this in mind, over the past year we have continued to set the stage for the next generation of young forest on the Merck Forest landscape. Between four sessions of Game of Logging and the work of Merck Forest staff and volunteers, we have started clearing mature forests abutting the current shrubland habitat along the Stone Lot road. This work will contribute toward a more substantial gradient of regenerating forest stands of varying age and formation. As one area grows to become unsuitable for shrubland species, there will be a connected area for these species disperse into. It also complements patch cuts completed in close proximity beyond the northern border of the property of Wind Gap Farm. Such a gradient is much more desirable than a hard transition between habitat types produced with disjointed patch cuts, and at a larger scale, achieves a diverse mosaic of habitat types that lends directly to biodiversity and long-term resiliency. It sounds complex, but the intent is simple: as forests ebb and flow over space and time, shrubland species will be better able to adapt to these natural changes and persist on the landscape.

Notably, 2.2 acres of this work is being funded by the Natural Resources Conservation Service EQUIP program, which covers a small, much appreciated, portion of the costs (fuel, equipment, staff time) associated with planning and completing the work. And all of this work, from soup to nuts, from scientific inquiry to sawing and skidding the trees, is being completed ‘in house’, with the same staff, wearing all hats. This is no small feat. While we are operating at capacity now, given limited staff time and resources, we continue working towards refining our approach and leveraging the means to scale this work in the coming years. Being resourceful and true to mission, we have engaged volunteers and students in the work along the way. These folks have helped to create habitat features and to control invasive bush honeysuckle (Lonicera sp.) that stand to benefit from the newly opened canopy. As such, this is a collective effort and students have an opportunity to both participate in, and more importantly, learn firsthand about the conservation efforts underway. An additional benefit of this habitat work is that it also provides the requisite fuelwood for our rec cabins, staff housing, visitor center, maintenance building, and sugaring operation. A whopping 60 cord are consumed annually and must be sourced from the property on a near continual basis. Anytime we undertake a forest management activity, we must maximize the benefits of the work so as to meet our needs on many fronts.

Shrubland habitats benefit many other taxa in addition to birds; there are too many to go into here. Small and large mammals, from herbivores to carnivores, as well as amphibians, insects, plants and fungi benefit from, if not depend upon, shrubland habitat. Here, again, is another layer of added benefits of this work.

Finally, I am dreaming of establishing a dedicated birding trail on property. Given the close proximity of the Stone Lot area to the visitor center and diverse array of other bird habitats: grassland habitat on the farm, the mature northern hardwoods (including Merck Forest’s sugarbush) south of the farm, and old fields on the periphery of the farm and the Discovery trail, we have a prime opportunity to share our avian diversity and our conservation work with a wide audience. The idea is entering into the planning phase now while we accrue the funds to cover staff time and material necessary to implement the work.

Literature Cited

Roberts, H. P., & King, D. I. (2017). Area requirements and landscape-level factors influencing shrubland birds. Journal of Wildlife Management, 81(7), 1298–1307. https://doi.org/10.1002/jwmg.21286

Smetzer, J. R., King, D. I., & Schlossberg, S. (2014). Management regime influences shrubland birds and habitat conditions in the Northern Appalachians, USA. The Journal of Wildlife Management, 78(2), 314–324. https://doi.org/10.1002/jwmg.658