A Quantitative Analysis of the Geomorphic Agency of the Mud-Nesting Swallows in Central Texas
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This dissertation provides a quantitative analysis of sediment erosion, transportation, and deposition conducted by the three mud-nesting swallows of Central Texas, namely the barn swallow (Hirundo rustica), the cave swallow (Petrochelidon fulva), and the cliff swallow (Petrochelidon pyrrhonota). The study area for this research is within the city limits of San Marcos, Texas, which straddles the Balcones Escarpment separating the Edwards Plateau from the Blackland Prairies. Swallows were investigated for their geomorphic role on the landscape, specifically, how much sediment is existing at the colonies positioned under fifteen bridges and one parking garage, what is the annual sediment transport per site, and is there a significant difference between cup-shaped and gourd-shaped swallow mud-nests. This dissertation is a contribution to the growing subdiscipline of zoogeomorphology, the study of animals as geomorphic agents. Little research has directly investigated any form of avian zoogeomorphology. Swallows, although commonly found in academic literature, have yet to be analyzed for their role in mud and clast transport for use in nesting. This dissertation aims at quantifying this geomorphic process.