NORTH CAROLINA – For every stage of forest succession, there’s a bird species that needs it. The blue-gray gnatcatcher, eastern wood-pewee, great crested flycatcher, summer tanager and white-breasted nuthatch are all associated with mature forests.
USDA Forest Service scientist Roger Perry led a study published in Forest Ecology and Management on the long-term effects of different forest regeneration methods on mature forest birds. Coauthors include retired SRS scientist Ron Thill, Julianna Jenkins of the Pacific Northwest Research Station, and Frank Thompson of the Northern Research Station.
Populations of forest birds have been declining since 1970. In 1993, Perry and Thill began a long-term study on the Ouachita and Ozark-St. Francis National Forests to see how birds respond to timber harvests.
They planted plots in the Ouachita and Ozark National Forests that were treated with four types of timber harvest, ranging from more intensive to less intensive: clearcut, shelterwood, single-tree selection and group selection.
“If you can’t identify birds by calls, you really can’t do a bird survey – especially in forests,” says Perry. “It’s rare that you actually get to see the bird. They’re always calling and singing up in the trees.”
Over the course of 16 years, Perry and his colleagues returned to the plots 35 times to count the birds found in each plot. Each year, the scientists tallied and analyzed species counts. Very few other studies have examined responses of forest birds to timber harvest for such a long period of time.
Although five species benefited from all harvests, including the intensive harvests, less intensive harvests were better for the majority of the eighteen bird species studied.
Using a variety of methods to harvest timber produces varied habitats that maintain the full suite of forest birds. However, maintaining some mature forests with well-developed midstories is also important.
“Diversity of the landscape equals diversity of birds,” says Perry.
Forest managers often manage for early successional habitats, partly for the sake of birds and other wildlife. Timber harvesting creates favorable conditions for bird species that prefer early successional habitat, as Perry and Thill found in an earlier related study.
The current study is part of a suite of studies produced for the Ouachita National Forest. Besides forest birds, studies addressed small mammals, pine regeneration, hydrology and visual quality.