What Can Birds Tell Us About Forest Health?

A new model uses bird surveys to gauge forest health at Wild Rivers Legacy Forest.

“You have to get out in the woods early to do a bird survey,” said Ron Eichhorn. “You rarely see the birds, you have to listen for them, and they are most vocal in the early morning. So you’re driving the logging roads in the dark, keeping an eye out for downed logs, to get to your survey site before sunrise.”

Ron and his wife Joan Berkopec are birders who have volunteered at Wild Rivers Legacy Forest in northeast Wisconsin for the past two years. They are helping The Nature Conservancy and Erin Giese, Biodiversity Research Specialist at the Cofrin Center for Biodiversity at the University of Wisconsin-Green Bay, survey the bird life in this 64,000-acre forest, which the Conservancy worked with the State of Wisconsin and two timber investment management organizations (TIMOs) to protect in 2006.

Erin, Dr. Robert Howe, Dr. Amy Wolf and Nicholas Walton at the Cofrin Center for Biodiversity and Nick Miller, Nature Conservancy conservation science director in Wisconsin, have developed a model that uses the absence and presence of a suite of bird species to gauge forest health. The model is based on an earlier one developed by Dr. Howe and other researchers in 2007. The Conservancy is using this model to determine whether its methods for conserving forests in northern Wisconsin are protecting forest health and diversity.

“Up to this point, we haven’t had a rigorous, cost effective and meaningful way to assess forest health,” said Miller. “This model is providing a tool we can use to do that here in Wisconsin and at other hardwood-hemlock forests in the western Great Lakes region.”

Wild Rivers Legacy Forest was a departure from the Conservancy’s traditional approach to protecting land by buying it. While 5,629 acres in Florence County were purchased by the state, the other 59,000 acres were protected using a working forest conservation easement held jointly by the state and the Conservancy. The TIMOs own the land and manage it for timber production, and the easement is designed to ensure that forestry activities are conducted in ways that protect wildlife habitat, water quality, public access for recreation and forest health and diversity.

“Using Erin’s model, we can compare forest health on the state-owned land, the TIMO-owned land covered by the easement and on other lands in the area that are not protected in any way to see if we are meeting our conservation goals,” Miller commented.

So what can birds tell us about the health of a forest? Quite a bit, according to Miller. Take the Blackburnian warbler, for example, a signature species of Wild Rivers Legacy Forest.

“During the bird surveys, when I came across a big, old hemlock in my survey area, I would find a Blackburnian hanging out up in the treetops,” said Miller. “Blackburnian warblers only occur in areas where you have big conifers and a lot of contiguous forest. Once you slice and dice the woods up with roads and big clearcuts, they’ll be gone.”

Birds are a useful tool for determining forest health. They are diverse and very vocal, singing boldly to stake claim to their preferred forest territories. And they require different types of habitat to survive. Some birds need a dense, intact layer of vegetation on the forest floor, others need the presence of large conifer trees like hemlocks, and others require a closed canopy with no gaps in the forest. Birds, especially in spring when they are breeding, are also sensitive to disturbances in their forest habitat including unsustainable logging, development, invasive species and climate change.

Over time, bird surveys at Wild Rivers Legacy Forest will help the Conservancy and other forest managers track forest condition and assess the impact that different types of management are having on forest health and diversity.

“It’s too early to say anything conclusive about the impact our various protection strategies are having on forest health at Wild Rivers,” Miller said. “We will need to look at long-term trends over time. But with just two years of data under our belts, it appears that the state-owned and TIMO-owned lands covered by the easement are faring well in terms of forest health, while the unprotected lands are showing more degradation.

Ron and Joan have also helped Dr. Howe with bird surveys in the Nicolet National Forest for 25 years, and can attest to the valuable information bird surveys can provide.

“The knowledge we’ve gained over time at the Nicolet is amazing,” Ron said. “Forests are maturing and changing, and the birds are changing right along with them and, best of all, because of the surveys, that information is all being recorded.”

“Joan and I like knowing that, in the future, the information we’re gathering at places like the Nicolet National Forest and Wild Rivers Legacy Forest will be useful to the Conservancy and other state and private managers to keep the forests healthy, especially in the face of climate change.”

Click here find the Cofrin Center for Biodiversity web site and learn more about how birds are helping researchers measure forest health in the western Great lakes region.