Forest Birds: The Spice of Life!
When you hear the phrase, “forest birds,” what comes to mind? Tall, mature oaks and pines spanning ridge tops? Riverbank guardians of sycamore and willows? Thick, young stands of aspen and birch? Low-lying bottomlands of red maple and black gum? The amazing assortment of plant communities in the Chesapeake Bay watershed sets the stage for the cast of birds that use these forests for nesting, brood-rearing, feeding and cover throughout the year. From the scarlet tanager to the ruffed grouse and from the blackburnian warbler to the wood duck, the spectrum of birds that call our Bay watershed home (for at least part of the year) depends on the quality and diversity of our woods and waters.
“Variety is the spice of life” is a saying that holds true for birds, too. When most folks imagine forest birds, they think of small birds living in large swaths of unbroken, mature woods. And that picture holds true for certain kinds of birds or at certain times of the year – such as Forest Interior Dependent Species, or FIDS, which require the climatic conditions and plant diversity found in larger acreages far from forest edges in order to successfully reproduce (50-100 acres of mature forest, 70-80% canopy closure, >300’ from the edge).1 However, even FIDS take advantage of plentiful food sources, such as protein-rich insects, other invertebrates and fruits that are found in canopy openings and nearby cutover areas, to feed their fledglings and then fuel up for migration.2 A more complete vision of healthy forest bird populations includes balanced, successional age classes.
Defining forest age classes and succession is not a perfect science, but there are a few guidelines that can help us form a mental picture. Most resources would consider a young forest to be a regenerating forest that is 0 to 10 years old. This early successional stage of grasses, shrubs and tree seedlings/saplings could last 15 to 20 years, depending on the growing conditions. An intermediate age class (think “teenage” trees!) would be approximately 10 to 50 years old. Sometimes this age class is called a “no man’s land” for wildlife – the multiple layers of vegetation that provide the food and cover found in a mature forest have not fully developed. Yet, birds and other wildlife will make use of these woods, especially with carefully planned patch cuts, thinning or invasive plant control. Eventually, after 50+ years, a mature forest takes shape. At some point, these older growth forests reach a “climax” point, give way and make room for new seedlings growing up through the understory. And the cycle continues…
Under natural conditions, forests of all ages are affected by periodic disturbances like severe weather (ice storms, high winds/tornados, flooding, lightning strikes), beaver activity, insect/disease infestations and wildfire that create openings, or gaps, in forest canopies. Under human influence, timber harvests serve as another source of disturbance. Wildfire suppression and habitat fragmentation caused by land development have negatively affected both the dynamic progression and the integral continuity of forest plant communities. When individual trees or stands of trees are removed or manipulated in a sustainable way with professional guidance or a management plan, they can provide wildlife benefits that replicate those of natural disturbances.
For more information about forest birds, preferred nesting habitats, habitats used post-fledging and special habitat considerations, take a peek at this easy-to-read-chart! 3
The “forest edge” is a transitional area from an area of woodland or forest to an area of fields or more open spaces. Typically, edge increases opportunities for all kinds of predators to feed on eggs, nestlings, as well as adult birds. Nest parasitism, when one bird species lays their eggs in the nest of another bird species (e.g. brown-headed cowbird), is also higher along the forest edge. However, several species of birds and other wildlife take advantage of this zone, which can act as a corridor between food and cover. Sound forest practices, such as softening or feathering the boundary between land management units, can help reduce some of the negative effects of a hard edge created by timber harvests and land development. Avoiding further forest fragmentation should also be considered, whenever possible.
In a nutshell, the term “forest birds” can include those that use very young forests, “teenage” forests and mature forests. There is even a place for the forest-edge specialists. Though these species may use one growth stage for the majority of the year, or for a specific purpose such as nesting, a mosaic of forest successional stages is crucial for healthy, reproductive bird populations. For more information about the forest successional stages, check out Forest Succession and Management from Cornell University or Forest Stewardship: Wildlife from Penn State Extension.
So what’s a landowner to do? Check out additional resources in the special edition of Forests for the Birds newsletter for management recommendations and programs that specialize in developing habitat for birds that inhabit young forests, mature forests and everything that grows in between!
- Stoleson, Scott H. 2013. Condition varies with habitat choice in postbreeding forest birds. The Auk. 130(3): 417-428. https://doi.org/10.1525/auk.2013.12214.
- Jones, Claudia J, J. McCann, S. McConville. June 2000. A Guide to the Conservation of Forest Interior Dwelling Birds in the Chesapeake Bay Critical Area. Maryland Department of Natural Resources. https://dnr.maryland.gov/criticalarea/Documents/forms_navbar/tweetyjune_2000.pdf
- Treyger, S.M. 2019. Managing Forests for Birds: A Forester’s Guide. Audubon New York. https://ny.audubon.org/sites/default/files/free_guide_forest_management_new_york_birds.pdf