Date of Award

January 2019

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Gary Ritchison

Department Affiliation

Biological Sciences

Second Advisor

Charles L. Elliott

Department Affiliation

Biological Sciences

Third Advisor

David R. Brown

Department Affiliation

Biological Sciences

Abstract

American Kestrels (Falco sparverius) are small falcons with a vocal repertoire known to consist of three different vocalizations: whine, chitter, and klee calls. However, the characteristics and contextual use of these calls have not been quantified. To determine the characteristics of these calls and better understand possible functions, I conducted a combined observational and experimental study of American Kestrels in Madison County, Kentucky, from February to July 2013. I observed kestrels and recorded all vocalizations uttered by males and females during different breeding stages and different behavioral contexts. In addition, I conducted playback experiments using the whine, chitter, and klee calls, and presentation experiments with models (study skins) of conspecifics and potential nest predators (human). I found that the characteristics of vocalizations of males and females were similar, but the chitter calls of males were at a higher frequency than those of females. Sex and call context had significant effects on the use of calls and number of calls per bout, with klee calls used significantly more often and with more calls per bout during heterospecific contexts than during either close or distant intersexual interactions. Whine calls were used more during close and distant intersexual interactions than during heterospecific interactions. All chitter calls uttered by males and females were in either close or distant intersexual contexts. Use of klee calls during encounters with other species near nests, particularly humans and Red-tailed Hawks (Buteo jamaicensis), suggests that they serve an aggressive function. Whine calls appear to be important for communication among male, female, and fledgling American Kestrels and appear to serve in soliciting the approach of a mate or, for fledglings, an adult. Chitter calls appear to play a role in pair formation and communication between mates before and after females begin incubating eggs, possibly informing mates of their approach or, as with whine calls, soliciting the approach of a mate. Analysis of how American Kestrels use and vary the characteristics of calls based on sex, behavioral context, and breeding stage improves our understanding of their function and how kestrels might vary call characteristics to convey information to conspecifics.

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