The Hawk-Snake Game: Responses of Female House Wrens (Troglodytes aedon) to Simulated Nest Predators

Josephina Fornara ’23

Student: Josephina Fornara ’23
Research Mentor: Dustin Reichard (OWU Department of Biological Sciences)

I spent my summer studying how mother house wrens — a common backyard songbird — respond to two different nest predators. I compared how the wrens defended their nests against a model of a black rat snake versus a taxidermied Cooper’s hawk, both of which frequently prey on young wrens. Hawks also pose a significant threat to adult wrens, whereas snakes do not. The female house wrens frequently dove at and hit the snake model but never demonstrated these defense behaviors against the hawk model, suggesting that house wrens change their behavior to match the perceived level of risk to themselves and to their nestlings.

Surviving encounters with predators is a problem faced by most — if not all — animals, including humans. Here, we compared the anti-predator responses of female house wrens (Troglodytes aedon) to two different simulated nest predators: a black rat snake (Pantherophis obsoletus) and a Cooper’s hawk (Accipiter cooperii). Both predators pose a significant threat to house wren nestlings; however, unlike snakes, hawks also pose a significant threat to adult house wrens. We predicted that mother house wrens would defend their nests less aggressively against a hawk than against a snake in order to ensure their own survival and to maximize their lifetime reproductive success. To observe anti-predator behaviors, female house wrens with 3-6 day old nestlings were presented with a predator model for seven minutes. We recorded the defense behavior of each female, including the amount of time she spent responding to the predator model and how many times she hit or dove at the model. Female house wrens frequently hit or dove at the snake model, but never demonstrated those defense behaviors against the hawk model. These results suggest that female house wrens modulate their anti-predator behavior to match the perceived level of risk from different predators, which is the strategy that should maximize lifetime fitness.