Managing Forests for Birds
The majority of OBCI’s priority species rely on forests, and the All-Bird Conservation Plan shows Southeast Ohio has the greatest potential for forest habitat restoration and protection. OBCI works with local and regional partners to educate land managers of public and private property about managing forests to improve bird habitat, especially for OBCI priority species such as the cerulean warbler.
OBCI has partnered with the Ohio Division of Wildlife, Ohio State University (School of Environment and Natural Resources, and Terrestrial Wildlife Ecology Lab), The Nature Conservancy in Ohio, Ohio Department of Natural Resources, OSU Extension, and the Ohio Biodiversity Conservation Partnership to design and illustrate a guide written by Amanda Rodewald entitled “Managing forest birds in Southeast Ohio: A Guide for Land Managers”. A full-length guide and a summary of management recommendations are both available. As a follow-up to the guide, OBCI & it’s partners produced a short video series that featured several Ohio landowners and focused on the importance of managing forests for birds. Additional information as well as the videos themselves can be found here.
Forest succession is the change in the structure and composition of forests over time. Understanding how succession influences avian communities is essential to effectively manage forests for birds and other wildlife. Because many bird species require specific habitat attributes, forests at different successional stages favor different bird species by virtue of the resources they provide. No matter how a forest is managed, whether actively or passively, certain species will be favored and others discouraged. The best strategy depends upon the management goal.
Early-successional Habitats for Shrubland Birds
- In harvests that are regenerating, encourage growth of native hardwood vegetation rather than planting conifers. Allow dense woody vegetation to regenerate in some areas, as density of shrubland birds increases with woody stems during the first several years of regeneration Although native and non-native plants both contribute to vegetative structure, native plants offer better food resources to birds and their insect prey. Because exotic plants can quickly invade following disturbance, managers should use species-specific recommended techniques to remove exotic plants both before and after harvest.
- For sites permanently managed as successional habitats, introduce disturbance at 6-8 year intervals. Abundance of shrubland specialists declines sharply after 6 years post-harvest.
- When possible, avoid creating small (<12 acres; 5 ha), narrow (<300 ft wide; 100 m), or irregularly-shaped shrubland patches. A better strategy is to manage for patches large enough to provide habitat >250 ft (75 m) from edges. Smooth or straight edges of harvests also will allow greater numbers of territories to be accommodated. Favoring square or circular patches rather than rectangular or irregular ones will increase the interior habitat of clearcuts without necessarily increasing harvest area (see box at right).
- When possible, cluster harvests and shrubland patches within particular management areas or zones. Providing multiple patches within 0.3-0.6 miles (0.5 -1.0 km) may promote landscape
connectivity for shrubland birds.
- Recognize that these recommended strategies (i.e., creating larger and more regularly shaped shrubland patches or clustering of patches) also have the potential to benefit mature forest dependent species in managed forest landscapes by reducing the amount of edge and fragmentation.
- Engage in landscape-scale and long-term planning to ensure that the needs of early and late successional wildlife are met.
Mature Forests for Late-successional Birds
- Efforts to manage local habitat features, such as forest structure, are an important piece of sustaining mature-forest breeders. In the forested landscapes (>70% forest cover) of southeast Ohio, structural attributes of forest (i.e., canopy structure, tree size, vertical complexity) had strong relationships with density and nest survival of sensitive species.
- Features generally associated with older forests may be important habitat components for mature forest breeders, such as cerulean warbler. These old-forest characteristics include a heterogeneous canopy, diverse understory vegetation, grapevines, and emergent large trees. Thus, using longer rotation ages (>100 years), as well as specific harvest prescriptions (e.g., single tree and group selection) and timber stand improvement practices (e.g., thinning and crop tree release) are likely to encourage the development of these features.
- As described in the section on “managing shelterwood harvests”, white oak should be emphasized in management because it is a favored nesting tree for cerulean warblers and other canopy-nesting birds. (see next chapter for additional details about floristic composition of stands).
- Several sensitive species breeding in mature forest would benefit from creating canopy gaps (>430 ft2, 40 m2) through single-tree or group selection cuts.
- Based on results from the cooperative Cerulean Warbler Forest Management Project (Boves 2011), recommendations for Appalachian forested landscapes specify that forests supporting >2 territories per 10 acres (>5 territories / 10 ha) of cerulean warbler should be managed without harvesting and in ways that minimize disturbance. On forest stands with fewer territories, management should reduce basal area to 56-78 ft2 / acre (13-18 m2 / ha) while retaining large overstory trees (>16 inches dbh; >40cm dbh), especially of white oak. Because identifying the best management course depends upon bird densities, coordination and cooperation with wildlife biologists may be necessary.
Shelterwood Harvests for Early and Late-successional Birds
A shelterwood harvest is a cut that retains an overstory of maturing trees. This technique allows new stems to grow under the cover of the remaining trees. In traditional shelterwood harvests, residual overstory trees are typically removed within 10-30 years.
- Partial harvesting (~50% stocking level), such as the shelterwood technique, can be used to provide habitat to both early-successional birds (e.g., prairie warbler, Eastern Towhee) and canopy-nesting species usually associated with mature forest (e.g., yellow-throated vireo, scarlet tanager). In southern Ohio, reducing basal area from 100-143 ft2 / acre to 39-70 ft2 / acre (23-33 m2 / ha to 9-16 m2 / ha) supported greater numbers of both shrubland and canopy-nesting species than unharvested mature forest.
- Recognizing that overstory is typically removed for oak regeneration within 5-10 years, shelterwood prescriptions need to ensure that nesting habitat is maintained across space and through time within the landscape.
- Favor white oaks rather than red oaks in shelterwood harvests, as white oaks (white and chestnut oaks) were strongly favored for nesting and foraging by most canopy nesting species. Red oaks (Northern red, Eastern black, and scarlet oaks) also may depress nesting success of canopy nesting birds.
- When possible, retain large diameter trees (>15 inches dbh; >38 cm dbh), which are most heavily used for nesting by canopy birds, including the Cerulean Warbler.
- In cases where there is wide latitude in choice of harvest location, avoid older forests with canopy gaps and/or those on northeast-facing slope, because these tend to be most heavily used by the declining cerulean warbler. Instead, shelterwood harvests are better implemented in areas that lack steep slopes (> approximately 15%) and/or have few canopy gaps, where they are more likely to create or improve habitat for species requiring heterogeneous canopies.
Landscape Mosaics and Structurally Complex Habitats for Post-fledging and Post-breeding Birds
- Manage mature forests in ways that promote structural complexity, which encourages microhabitats that provide dense understory vegetation. Examples include treefall gaps, riparian thickets, and natural patches of shrubs. Because some of these features are typical components in old, uneven-aged forests, consider allowing stands to reach ages greater than 100 years.
- Allow roadsides and other human-associated edges to develop the thick vegetation that is heavily used by post-breeding birds. There appear to be no strong size requirements for use by
- When consistent with other management goals (e.g., oak regeneration), consider using silvicultural techniques to create areas with dense vegetation. Group-selection harvests and shelterwood harvests may be good examples of this. Although use of these harvest types has not been specifically studied during this stage in the annual cycle, changes in habitat structure associated with those silvicultural techniques are consistent with features preferred by post-breeding and post-fledging birds.
- Regarding harvest size, be attentive to needs of other species and during other stages of the annual cycle. Post-fledging birds do not seem to require large patches of successional habitat and can use dense vegetation within mature forests. Consequently shrubland habitats are probably best managed according to recommendations for early-successional breeders.
- Engage in landscape-scale planning to ensure that sufficient forest is retained to permit movement through the landscape. Not only are independent juveniles known to make extensive movements, but numbers of post-breeding birds using harvests was positively related to forest cover within 0.62 miles (1 km).