Graduation Date

Summer 2020

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Wildlife

Committee Chair Name

Jeff Black

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Barbara Clucas

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Mark Colwell

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Wildlife

Abstract

While the elaborate songs of male passerines are well documented for their role in intrasexual resource competition and mate attraction, vocalizations used in female competition are poorly understood. Research has suggested that the female-specific rattle call of Steller’s jays (Cyanocitta stelleri) is used in competition for access to a territory and mate. I describe structural properties of the rattle call, and compare life history traits of individual females to rattle call occurrence. I used two rates to quantify rattle call occurrence from 20 females: rattles per observation period (RPO), and proportion of observations with a rattle call (POR) from August 2017 – April 2018 in Arcata, California.

Based on spectral analyses, rattle calling consisted of rapid-fire call notes given at 37 – 98 notes per second (mean = 68 ± 17 SE, n = 16) for 0.80 – 2.14 seconds (mean = 1.55 s ± 0.39 SE, n = 16). Jays produced call notes at a peak frequency of 14,855 kHz (± 2,716 kHz SE, n = 16) and fundamental frequency of 3,850 kHz (± 205 kHz SE, n = 16). The rattle call was sometimes preceded by a series of guttural notes.

I observed 158 rattle calls from 18 of 20 females during 49 out of 162 focal animal observation periods. The likelihood of observing rattle calls depended on life history traits of the sender. I identified the receiver of the rattle call on 42 occasions; 18 rattle calls were directed at males (57%) and 24 were at other females (43%). When paired females rattled at a male, it was always at their mate. When unpaired, floater females rattled at a male, it was always at a territory owning male. Female Steller’s jays were not observed rattle calling in the absence of conspecifics. Overall, novice females (i.e. beginning their first breeding season) had a higher rattle rate than experienced females. Floater females rattled in more observations than territorial females.

During back and forth rattle contests between novice and territorial females, novice females rattled as much as, or more, than their territorial opponents in several instances. In the two dyads where the territorial female did not rattle more than the novice intruder, the novice females ended up usurping the territorial females, and nesting in their territories with their mates.

Investigation into female vocalizations, such as the rattle call, may bolster our understanding of factors limiting survival and reproduction in females. The characteristics associated with higher rates of calling may indicate drivers for evolutionary change. In this case, floater females limited by nesting experience, and paired females defending a territory apparently used the rattle call when competing for access to mate, territory, and nesting resources.

Citation Style

JWM

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