Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Organismal Biology, Ecology, and Evolution

Department or School/College

Division of Biological Sciences

Committee Chair

Dr. Erick Greene

Commitee Members

Dr. Erick Greene, Dr. Brett Tobalske, Dr. Jon Graham


communication network, alarm call, microphone array, Poecile atricapillus, Sitta canadensis


University of Montana

Subject Categories

Behavior and Ethology


To avoid predation, many animals have evolved complex systems of anti-predator communication. Alarm calls are a key component of anti-predator behavior in many birds, and can provide detailed information about predators. Additionally, many birds and mammals produce and respond to each other’s alarm calls, creating a complex communication network. Furthermore, individuals may give alarm calls in response to the alarm calls of others nearby, without actually seeing a predator. This makes possible the spatial spread of alarm information, which can result in complex communication networks extending over a large area. However, this requires suitable habitat in which birds will be present to detect and produce alarm calls. Gaps in habitat may preclude the functioning of these networks if they do not contain birds.

To quantify the extent of alarm networks and assess the impact of forest gaps, I conducted a series of playback experiments wherein I broadcast alarm calls to forest bird communities and monitored alarm responses at a distance away, either across a gap or same-size tract of continuous forest. I predicted that alarm responses would be lower across gaps than through forest, and that regardless of the presence of a gap, response will also decrease with increasing distance from the site of alarm call playback. Birds did respond over large distances through continuous forest, but contrary to my predictions, responses across gaps were actually greater than through continuous forest. This implies that, rather than impeding communication through networks, gaps may actually facilitate the spatial spread of information. To my knowledge, this study is the first to explicitly investigate space or habitat structure as a component of communication networks. My results suggest that communication networks allow for a kind of indirect communication, whereby individuals are able to share information over great distances through intermediary signalers.



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