Date of Award

January 2015

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Gary Ritchison

Department Affiliation

Biological Sciences

Second Advisor

David R. Brown

Department Affiliation

Biological Sciences

Third Advisor

Charles L. Elliott

Department Affiliation

Biological Sciences

Abstract

Anti-predator defense is an important adaptation in group-living organisms. Some species of flocking birds use referential calls to communicate predator presence and the level of threat posed by predators. Previous studies have revealed that two species in the corvid family, American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus), use referential calls to convey information about predator presence and level of threat. Because of their intelligence and flocking behavior, Blue Jays, like American Crows and Siberian Jays, may use referential calls to communicate raptor presence and threat. During the non-breeding seasons of 2014 and 2015, I recorded and subsequently analyzed the vocal responses of Blue Jays to study skins (N = 7) that varied in size and the level of threat they pose. Experiments were conducted at seven different locations in Madison County, Kentucky. The mean number of jays present was 2.6 (range = 1 – 6), and jays uttered five different vocalizations, with ditonal and monotonal jeers given most frequently. The rate at which jays uttered ditonal jeers differed significantly among trials (P < 0.001), with the highest rates during trials with an Eastern Screech-Owl (Megascops asio) and a Sharp-shinned Hawk (Accipiter striatus). I found no differences among trials in the characteristics (duration, low frequency, high frequency, and peak frequency) of either ditonal jeers or monotonal jeers. Assuming that calling rates vary relative to the degree of threat posed by aerial predators, my results suggest that Eastern Screech-Owls and Sharp-shinned Hawks represent the greatest potential threats to Blue Jays in my study area, and other raptors used in my experiments, including American Kestrels (Falco sparverius), Cooper’s Hawks (Accipiter cooperii), Red-tailed Hawks (Buteo jamaicensis), and Great Horned Owls (Bubo virginianus), pose lesser threats. Although Blue Jays in my study did respond differently to different predators, their vocal responses were not functionally referential, i.e., the same calls with the same characteristics were used when responding to different predators, only the calling rates differed among trials. Thus, rather than providing conspecifics with specific information about predation risk, Blue Jay calls, especially ditonal jeers, appear to be directed at predators and primarily serve to harass and provoke them into moving elsewhere.

Included in

Ornithology Commons

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