Prescribed burning could be a good way to restore oak forests in the eastern U.S. -- but it might also have some unwanted ecological effects. The first study of bird recovery after prescribed burning shows that it can reduce populations of ground-nesting birds.
This work is presented in the October issue of Conservation Biology by Vanessa Artman, who did this work while at Ohio State University in Columbus and is now at Kenyon College in Gambier, Ohio, and her co-authors.
Decades of fire suppression in eastern U.S. deciduous forests have shifted the dominant tree from fire-tolerant oaks to fire-intolerant species such as red maples. Experimental prescribed burns are being assessed to see how well they restore and maintain oak-dominated forests. Biologists are particularly concerned about the effects on the Neotropical migrant songbirds that breed in U.S. forests, some of which have declined over the last 25 years.
Artman and her colleagues investigated the effects of prescribed burns on forest birds in four study sites: two in the Wayne National Forest and two in the Vinton Furnace Experimental Forest in southcentral Ohio. The researchers burned 50-75-acre areas either frequently (yearly for four years) or infrequently (at the beginning and end of the study period); the historical fire frequency was about once every five years. The researcher then monitored 30 bird species in both burned and unburned areas.
Artman and her colleagues found that after four years of repeated burning, three ground-nesting bird species declined by more than 80%: ovenbirds, worm-eating warblers and hooded warblers. The researchers attribute these declines to the fact that burning decreased the leaf litter, shrubs and saplings that the birds depend on.
Ovenbirds nest on the ground and use leaf litter to build and conceal their nests. Worm-eating warblers nest on the ground in high moisture areas, and the burns presumably dried them out and made them less suitable for nest sites. Hooded warblers typically nest within a few feet of the ground in dense shrub thickets, and the burns eliminated most of these.
The researchers also found that two bird species increased: American robins and eastern wood-pewees (the former went from being rare to being common, and the latter nearly doubled). The researchers frequently observed these birds feeding in burned areas, suggesting that fire improved their foraging habitat.
Artman and her colleagues conclude that long-term or large- scale prescribed burning could change the songbird community in eastern deciduous forests.
Artman's co-authors are: Elaine Sutherland of the U.S. Forest Service in Missoula, Montana, and Jerry Downhower of Ohio State University in Columbus.
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