PARENT SESSION
Poster Session 11: Disturbance Ecology
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Bird abundance and nesting success in experimentally manipulated long leaf pine understories.
Robinson, W. Douglas*,1, Rompré, Ghislain2, 1 Oregon State University, Corvallis2 University of Laval, Quebec
ABSTRACT- Longleaf pine ecosystems once dominated the southeastern United States, but few extensive natural forested areas remain. Many of the remaining stands have been degraded by fire suppression, which naturally occurred on a 2-5 year cycle. Bird community composition changes rapidly depending on time since the last fire, with specialist species appearing up to 4 years after fire and shrub-generalists persisting for much longer. Natural fires have been almost entirely eliminated from some regions and prescribed fire is difficult to conduct in regions near towns and cities. Several alternative methods for reducing understory vegetation have been proposed but their effects on biodiversity have not been measured. We evaluated bird responses to four understory removal methods: prescribed fire, mechanical clearing, herbicide, and a combination of herbicide and mechanical clearing. Our study sites were 10-ha longleaf pine plots (N=3 per treatment and 3 control plots) in southern Alabama. Burned plots had higher plant diversity but lower shrub cover than control plots. Mechanically cleared, herbicided, and mechanically cleared/herbicided plots had lower plant diversity and lower shrub cover than control plots. We monitored birds with point counts and spotmapping, and estimated breeding success by finding and monitoring nests in 3 years. Most understory bird species showed strong responses to the treatments while mid-story and canopy species rarely did. Avian abundance was significantly higher in burned stands one to three years after fire and was significantly greater than in mechanically cleared and control plots, but not greater than in herbicided stands. Community composition changed depending on treatments. The most sensitive species, Bachman's Sparrow Aimophila aestivalis, appeared only after fire. Patterns of nesting success varied in species-specific manners. We conclude that avian diversity is enhanced best when fire is used to control understory succession. Despite the drawbacks of using fire as a management tool, our experimental results show that fire creates situations which enhance avian diversity and productivity the best.
Key words: fire, habitat structure, nesting success, bird abundance