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Columns::September 22, 2003
Root of the problem: Researchers plant trees that help clean up toxic waste site
UGA, MCG study long-term impact of schizophrenia drugs
Two new faculty members are named Eminent Scholars in molecular genetics, biochemistry
New digital library collection looks at architectural sites, landscapes
Law professor briefs his students on legal ethics, civil procedure
Retirees
Kudos
Primary messages: Political scientist studies campaign communication strategies of presidential candidates
Movers and shakers
Campus News
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| Because the prothonotary warbler is found virtually nowhere other than forested wetland, it serves as a good indicator of the ecological health of the area studied by UGA researchers. This prothonotary warbler is building a nest. |
Song sung blue
Proposed water projects are bigger threat to local songbirds than timber harvesting
By Kim Carlyle
kcarlyle@uga.edu
Bottomland forests in the lower Mississippi alluvial valley are threatened by agricultural conversion, and much of the remaining
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Robert Cooper
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forest is actively managed by timber harvest. Recent UGA research shows that a bigger threat to local songbirds, however, may come from proposed projects that threaten the water to the region.
Robert J. Cooper, professor in the wildlife program of the Warnell School of Forest Resources, and Jill Gannon, a wildlife graduate student, investigated the effects of timber harvesting options in bottomland forests by measuring the reproductive ecology of prothonotary warblers (Protonotaria citrea) in the White River National Wildlife Refuge in Arkansas. The results were presented this past month in Savannah at the annual meeting of the Ecological Society of America.
The refuge consists of 60,000-plus hectares, almost entirely bottomland hardwood forest--mostly Nuttall oak, overcup oak and bitter pecan trees. The timber is actively managed for habitat diversity and oak regeneration, among other objectives. Regular flooding occurs in late winter and early spring.
“Most of the songbird species in this kind of forest are neotropical migrants,” says Cooper. “As a group, those birds are declining. Additionally, the amount of original floodplain forest in the Mississippi Valley has been reduced by about 80 percent. However, very few of the 200 or so species of neotropical migrants are federally endangered yet. We wanted to see what effects various land management options had on the prothonotary warbler population, because we know the best way to manage endangered species is to help them before they reach that critical level.”
Cooper and Gannon chose the prothonotary warbler as an indicator because of its relationship to this kind of forest.
“Virtually every ecosystem has at least one bird species that is so intimately tied to that system that they could be seen as ecological indicators,” says Cooper. “The prothonotary warbler is found virtually nowhere other than forested wetlands, and that is the primary makeup of this area. That is also why it is so important to assess the full effects of our land management decisions before they are implemented.”
Timber harvesting in the study was designed to mimic natural disturbances. Using both single-tree selection and small patch cuts--clear cuts of no more than five acres--the study found that while treated plots temporarily had fewer birds on them (because nest trees were removed), success and productivity of remaining individual nests seemed to be unaffected.
“As the forest grows back, we expect densities of forest birds to recover as well,” Cooper says.
However, nest success seemed to correlate with water levels in the system. For that reason, Cooper and Gannon believe that the three proposed water management projects on the White River--which would alter flows in the river and its floodplain--are a significant threat to the system.
One of the major proposed projects, the Grand Prairie irrigation project, would draw water directly out of the White River to irrigate about 240,000 acres of cropland. Other projects proposed or under construction on the White River are a navigation improvement project and a lock-and-dam project to promote barge traffic.
“We believe that protection is afforded to nests built over water,” says Cooper, “and that alternative abundant prey like fish and crayfish are available to some nest predators like raccoons. In dry periods, nests are relatively unprotected and alternative [aquatic] prey is not as readily available.”
The major cause of nest failure in the study was nest depredation by a variety of forest-dwelling predators, such as raccoons, woodpeckers and rat snakes. Years with normal flooding resulted in higher nest success, and dry years, or dry periods within wet breeding seasons, resulted in increased nest depredation.
“Results of our study already have been used to modify forest management plans on the refuge,” says Cooper. “I only hope they will be taken into account when these water management projects are reviewed as well.”
Proponents of the Grand Prairie irrigation project say it is necessary to preserve the region’s farm-based economy. Opponents say the project threatens the river basin. “If we listen to what this indicator is telling us,” says Cooper, “then the threat to the river basin is real.” |
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