Date of Award

January 2019

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Gary Ritchison

Second Advisor

Luke E. Dodd

Third Advisor

Charles L. Elliott

Abstract

Some species of birds have alarm calls that are functionally referential and provide their nestlings with information about the level of threat predators may pose. Although several investigators have examined the responses of nestlings of species with open-cup nests to the anti-predator calls of adults, few have conducted such studies with cavity-nesting species of birds. Therefore, the objectives of my study were to examine the vocal responses of cavity-nesting adult Tree Swallows (Tachycineta bicolor) to different nest predators, some able and others unable to enter nest cavities, and to examine the responses of nestlings to those vocalizations. My study was conducted from April to July 2016 at the Blue Grass Army Depot in Madison County, Kentucky. I conducted 68 trials at 22 nest boxes. Tree Swallows were exposed to models of four potential predators, including taxidermy mounts of a raccoon (Procyon lotor) and an eastern chipmunk (Tamias striatus), a study skin of an American Kestrel (Falco sparverius), and a rubber model of a black rat snake (Pantherophis obsoletus), as well as a study skin of an American Robin (Turdus migratorius) used as a control. Experiments began at nests when nestlings were 12 or 13 days old. To assess responses of adults and nestlings during trials, predators or the control were placed on or adjacent to nest boxes. The vocal responses of adults and the behavioral responses of the nestlings were simultaneously recorded. I found no differences in call rates or the characteristics of calls across trials, with the exception that rates at which alarm shriek (F4,33 = 3.4, P = 0.02) were uttered were greater during trials with the American Kestrels than during trials with the rat snake model (P < 0.05). In addition, I found no difference in the proportion of nestlings that crouched during trials across all predator models. These results suggest that adult Tree Swallows do not use a referential alarm call system, i.e., uttering different calls in response to different potential nest predators (F4,34 = 0.7, P = 0.60). Although the rate at which alarm calls were uttered differed among trials with different predator models, nestling responses did not differ. Such results suggest that adult Tree Swallows are also not encoding information about potential predators by varying call rate.

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