The sensory ecology of yellow warbler referential alarm calls

Lawson, Shelby Louise

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https://hdl.handle.net/2142/116193 Copy

Description

Title

The sensory ecology of yellow warbler referential alarm calls

Author(s)

Lawson, Shelby Louise

Issue Date

2022-07-08

Director of Research (if dissertation) or Advisor (if thesis)

Hauber, Mark E

Doctoral Committee Chair(s)

Hauber, Mark E

Committee Member(s)

• Bell, Alison M
• Ward, Michael P
• Gill, Sharon A

Department of Study

Evolution Ecology Behavior

Discipline

Biology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• brood parasitism
• referential alarm calling
• playback study
• yellow warbler
• frontline defense
• anti-parasitic defenses
• mental time travel, heterospecific eavesdropping

Abstract

Diverse animal lineages communicate using complex vocalizations, which can have structural and functional parallels with human language. One such set of communication signals is the functional reference call, which is a form of symbolic communication that has evolved repeatedly in vertebrates, including several times amongst birds. These calls denote specific objects in the environment, generally predators, and elicit behavioral responses from animals that hear these calls that are specific for the threat being referenced (e.g. hiding under cover from flying predators). Understanding the sensory ecology and developmental mechanisms that allow animals to process and respond to complex vocalizations can inform us about the evolutionary forces that drive the formation of intricate communication systems and, ultimately, language. Yellow warblers (Setophaga petechia), a small North American passerine species, produce referential “seet” calls to warn of a different type of danger – obligate brood parasitic brown-headed cowbirds (Molothrus ater). Brown-headed cowbirds lay their eggs in the nests of other species, leaving these hosts to care for the parasitic young. Yellow warblers produce seet calls in response to brood parasitic signals (cowbirds, their vocalizations, and conspecific seet calls) to warn nearby individuals of this specific danger. Female warblers that hear the seet call return to sit tightly on their nest to presumably prevent cowbirds from inspecting and parasitizing it. Previous work on seet calls in yellow warblers has shown temporal specificity in production of the calls, particularly during the egg-laying stage when cowbirds are most likely to parasitize nests. The majority of literature on yellow warbler seet calling has focused on the production and behaviors associated with seet calls in response to model presentations. However, the sensory-perceptual abilities of birds to discriminate and respond adaptively to vocalizations signaling different threats (e.g. parasite vs predator) and the ecological contexts that promote these abilities, have hardly been explored. I explored these questions by presenting playbacks of cowbird chatters, seet calls, chip (general alarm) calls, predator calls, and controls, to yellow warblers varying in sex and breeding stage, and measuring behavioral responses including latency to respond, alarm calling, and approach, and nest sitting defenses both at the time of playbacks and the subsequent morning. I also explored whether and how heterospecific eavesdroppers utilize and respond to neighboring yellow warbler seet calls as a defense against cowbirds at their own nests. Through the studies of my dissertation, I found that latency to respond, alarm calling, approach, and nest sitting defenses were affected by acoustic stimuli signaling brood parasitism (cowbird chatters and seet calls). Furthermore, similar to model presentations, yellow warblers used seet calls and chip calls towards acoustic stimuli of brood parasites and predators, respectively, with seet call production being mediated by the temporal risk of brood parasitism. Additionally, I found that red-winged blackbirds (Agelaius phoeniceus), a heterospecific species that often nests near yellow warblers, eavesdrop on seet calls of yellow warbler neighbors. Red-winged blackbirds also varied in the same behavioral response measures as yellow warblers towards signals for brood parasitism depending on their current risk of parasitism. Thus, the studies in my dissertation further our understanding of the sensory ecology of yellow warbler referential calling, and the functional contexts that both conspecific warblers and heterospecific eavesdroppers use when responding to anti-parasitic referential alarm calls.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Shelby Lawson

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