This blog was written by Defenders of Wildlife Southeast Interns, Hannah Naehring and Shannon Junco.
This summer we set out early to carry out field work in remote sections of the Pisgah National Forest. Our mission: deploy Autonomous Recording Units (ARUs) within stands of mature hardwood forests to find out which birds are in the region. ARUs are attached to trees and programmed to capture the songs of birds at dawn and dusk, periods when they are the most active. Once retrieved, the audio is analyzed to identify which types of birds are present.
But this year’s field season was anything but typical. The devastation wrought by Hurricane Helene had transformed the forest habitat, making it difficult to access our sites.
These songbird studies — which started in spring of 2024 and involve several partners — are part of a multi-year project to survey cerulean warblers and other neotropical migratory songbirds that breed in the Craggy Mountains and Big Ivy area of the Pisgah. The project initially set out to assess declining breeding populations and their presence in mature oak-hickory forests. Hurricane Helene, however introduced a new variable into the study that could give insights into the impact of natural disasters and large-scale disturbances on breeding habitat for these birds.
How did Helene affect cerulean warbler breeding habitat?
Many areas surveyed last spring are now littered with downed trees or disrupted by landslides and altered river systems. Although this new landscape was difficult for us humans to navigate, it did result in the creation of numerous openings in the forest known as “canopy gaps.” These gaps, created by the loss of standing trees, are part of the ecological dynamics of our Southern forests. The size and distribution of these gaps impact the use of the habitat by migratory songbirds. This year’s surveys provide an important snapshot on the impacts of this major event.
Ceruleans are known canopy-dwellers, in the spring males will perch in the tops of canopies singing their song to attract females. Gaps in the canopy within mature forests increase the complexity of the forest structure and may initially increase the amount of breeding and foraging habitat for Ceruleans.
How have debris removal and salvage logging impacted cerulean warbler breeding habitats?
In addition to the natural disturbance caused by Hurricane Helene, salvage logging and debris removal efforts were underway at several survey sites, including areas where Cerulean warblers and other vulnerable species were detected last year. While naturally occurring canopy gaps may prove to be beneficial to these resilient forest interior birds, salvage logging and debris removal may pose a threat to breeding habitat. These additional management actions can compound the impacts of the initial disturbance causing erosion, soil compaction and the introduction of non-native invasive plants.
These activities can also disrupt the natural successional processes that typically follow a disturbance. For example, downed trees provide cover for fledglings and support insect and spider communities, an important food source for many birds. By removing too many downed trees, both breeding and foraging habitat is negatively impacted.
How did this year’s survey differ from last year?
In 2024, before Helene, 62 sites were surveyed and cerulean warblers were found at six of them, along with many other focal birds throughout the study area. Hiking to these sites under normal conditions is rigorous. This year, we climbed the same steep mountains and crossed streams but with the added challenge of climbing over, or around, acres and acres of huge fallen trees. Though the data from 2025 has not yet been fully analyzed, we were able to access and re-survey 34 of the 62 sites from 2024 and survey 48 new sites.
What does the future of the cerulean warbler breeding habitat look like?
Sites where cerulean warbler presence has been confirmed should be given priority when considering land protections to preserve suitable habitat and wildlife connectivity. Additionally, incorporating climate-resilience strategies into forest management projects will be invaluable for species like the cerulean warbler. It has been suggested to the U.S. Forest Service that preservation of remaining mature oak-hickory forests in the study area will be highly favorable for ensuring the protection of breeding bird populations.
Defenders along with project lead National Parks Conservation Association and other partners, meanwhile, plan to continue these surveys into the future. There is also a desire to expand surveys to other regions adjacent to the Blue Ridge Parkway where breeding cerulean warbler populations are known to be established during peak months.
What can you do to help cerulean warblers and other migratory birds?
Do the songs of migratory birds call to you? Contribute to community science on your next outside adventure! Phone apps like Merlin and eBird can help you identify and learn about the birds you see and hear while contributing valuable data to science. Learning how to bird can help our feathered friends from wherever you are, including your backyard, local trail and vacation exploration. If you would like to get more involved in North Carolina, consider volunteering with Defenders’ Southeast field team! Email Defenders staff at southeastoffice@defenders.org.
