Term of Award

Spring 1999

Degree Name

Master of Science

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

C. Ray Chandler

Committee Member 1

Stephen P. Vives

Committee Member 2

Lorne M. Wolfe

Abstract

Migratory birds spend a significant part of each year in transition between their breeding and resting grounds. During this transitional period migrants rely on stopover sites to provide them with the necessary habitat to replenish lost energy stores, rest, and wait for favorable weather conditions before continuing migration. The majority of stopover work related to passerines in North America has occurred along coastal migration routes. Meanwhile, relatively little work has been conducted at inland stopover sites, areas which may be equally important to migrating birds. Kennesaw Mountain is an isolated geographically prominent peak located in the foothills of the southern Appalachian Mountain range that may provide important stopover habitat for migratory birds, as well as enable migrants to regain their desired migratory route during spring migration. The objectives of this research are to determine 1) if Kennesaw Mountain, a seemingly important inland stopover site in north Georgia, is being used disproportionately over the surrounding mountains, and 2) whether use of Kennesaw Mountain is attributable to its geographical prominence or specific features of its habitat.

During the spring months of 1997 and 1998, I used line transects to census migratory birds at Kennesaw, Lost, and Sweat Mountains to detect possible differences in the occurrence of migrants at each site. Censusing began 10 minutes before sunrise and was conducted every two hours thereafter until noon. In 1997,1 detected significantly more migratory birds (both the number of individuals and number of species) on Kennesaw and Lost Mountains than on Sweat Mountain. While during 1998, significant differences were detected only between Kennesaw Mountain and Sweat Mountain. In general, differences in the volume of migration among sites were greatest just after dawn and gradually decreased throughout the morning.

I did not find a significant difference in the overall volume of migrant individuals or migrant species among time periods within each site, however, the general trend for the number of individuals and species richness at Kennesaw Mountain and Lost Mountain was a peak shortly after sunrise followed by a gradual decline throughout the morning. Meanwhile, Sweat Mountain demonstrated little variation in the number of individuals or species richness throughout the morning during either year. However, the variation in weather among days within a site may act to confound these census data. Variable weather condidons had a significant effect on the occurrence of migrants on Kennesaw Mountain. During days with clement weather condidons (i.e., light winds and clear skies) there was a significant decrease in the number of migrant individuals occurring on the mountain throughout the morning. Meanwhile, during days with inclement weather conditions (i.e., heavy fog, strong winds, or rain) there was no temporally significant difference in the number of migrant individuals. Migrants were much more likely to remain on the mountain and continue foraging throughout the morning. These data suggest migrants are not initially attracted to Kennesaw Mountain due to its habitat.

In addition to censusing, I made observations from a small clearing on the southeastern side of Kennesaw Mountain to detect possible morning flight by largely nocturnal migrants. Data from morning flight observations and censusing on Kennesaw Mountain indicate that migrants typically began to approach the mountain shortly before sunrise, although most individuals did not arrive until shortly after sunrise. The peak arrival of migrants occurred within the first hour after sunrise and dramatically declined afterwards. While observations of morning flight were limited to areas between the east and south, migrants predominantly arrived from the SE and rarely from the east or south.

Observational and census data suggest that migrant birds approaching Kennesaw Mountain may be redetermining their desired migratory route following displacement by unfavorable winds. Moreover, these data suggest the initial attractiveness of Kennesaw Mountain to migrants is based upon its geographical prominence over the surrounding areas. Whereas the evaluation of habitat suitability upon approaching each mountain may be secondary and results in an individuals' decision to 1) perceive the habitat is suitable or necessary for stopover and land or 2) determine the habitat is unsuitable or unnecessary for stopover and continue flying until more suitable habitat is found. Results from this study emphasize the need for further investigation of these and other isolated prominent peaks in the southern Appalachian Mountain range to establish their significance to migratory birds.

Copyright

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