Fire is for the birds: Bird abundance doubled in severely burned areas of Southern Appalachia
In 2016, drought, a history of fire exclusion, and human activity collided in the southern Appalachians. More than 30 wildfires burned at least 80,000 acres, and fourteen people lost their lives because of the wildfires.
Indigo buntings are among the species that depend on early successional habitat, such as that created by fire or other disturbances, including timber harvest.
However, the aftermath provided researchers a unique opportunity to explore the effects of fire on Appalachian ecosystems. A study in Forest Ecology and Management shows that the number of birds and bird species doubled in severely burned areas. Katie Greenberg, a USDA Forest Service research ecologist, led the study.
The Camp Branch and Tellico wildfires burned in and around the Nantahala National Forest in western North Carolina. As they roared up steep, south-facing slopes and crept through coves, they left a mosaic of burn severities behind.
Greenberg and collaborators monitored birds and vegetation in both unburned and burned forests, studying areas of low, moderate, and high severity fires. In the high severity burn patches, 70% of trees died within five years, creating a pulse of light on the forest floor. Shrubs that thrive in high-light, disturbed forests – such as blackberries – re-sprouted swiftly, creating dense cover for birds.
After the fire, indigo buntings quickly came to the patches that had burned at high severity. Within two or three breeding seasons, chestnut-sided warblers, and eastern towhees had joined them. These three species are associated with a forest structure created by heavy disturbances.
Within five years of the wildfires, bird diversity in moderate- and high-severity burn patches was double that of unburned forest. Many other bird species – even those that are not considered disturbance-dependent – were also more abundant in higher severity burn areas. In contrast, low-severity fire had no detectable effect on bird communities.
To a human, this bird-friendly landscape is unfriendly. Imagine blackened snags poking up through a thorny thicket of interlocking blackberry canes and stump sprouts of trees. Any attempt to walk through this space will be rewarded with thorn pricks that can be felt through most clothing. But the birds love it.
“The lush, new vegetation growth – shrubs and an abundance of sprouts from dead or injured trees – likely attracts insects that in turn attract birds,” says Greenberg. Other studies show that adult birds bring their young fledglings into young forests where they can learn to forage under the dense cover of shrubs and tree sprouts.
Greenberg has contributed to several long-term, highly collaborative studies on fire and wildlife in the southern Appalachians. Some of them, like the Fire and Fire Surrogates research, were conducted nationally and funded by the Joint Fire Science Program.
In the Southern Appalachians, fires that do not kill a lot of mature trees do not create habitat for disturbance-dependent birds. “Study after study shows that, including this recent one,” says Greenberg.
An earlier study on the season of burn showed that low intensity burns – like most prescribed fires – don’t have much impact on forest structure, whether they occur during the winter or early spring. That’s likely because they don’t usually kill mature trees. In the southern Appalachians, fires do not have much effect on wildlife habitat unless they are severe enough to kill large trees and substantially reduce the canopy cover.
In the southern Appalachians, fires that do not kill mature trees do not create habitat for birds that depend on young forests and early successional habitat.
“Other research shows that timber harvests benefit birds in similar ways, if they substantially reduce the tree canopy cover,” says Greenberg. “In western North Carolina, we have a lot of mature upland hardwood forests – most trees are more than 100 years old. There are far fewer young forests today because of reduced timber harvesting over the past several decades.”
In the past, Indigenous people, and then Euro-American settlers, intensively managed the landscape, creating woodlands, open forests, and young forests.
“Without human influence, there wouldn’t be a huge amount of young forest in the Southern Appalachians,” says Greenberg. “Lightning-caused wildfires are rare in this area because our forests are moist and productive, and we tend to get so much rain during the summer thunderstorm season, when lightning most often occurs. Landslides, windstorms, and southern pine beetle outbreaks happen occasionally. They kill trees which creates that young forest habitat that many wildlife species depend on.”
The National Forests of North Carolina provided funding for monitoring birds on the Nantahala National Forest.
For more information, email Katie Greenberg at katie.greenberg@usda.gov.