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Date of Award


Document Type

Thesis-ISU Access Only

Degree Name

Master of Science (MS)


School of Biological Sciences

First Advisor

Charles F. Thompson

Second Advisor

Scott K. Sakaluk


Predation is a significant cause of nest failure in passerine birds, and thus, natural selection is expected to favor behavioral plasticity to allow birds to respond to perceived changes in predation risk. However, behavioral plasticity in response to perceived predation risk, and its potential fitness-related costs, remain relatively understudied. In a wild population of breeding house wrens, I tested the hypotheses that (1) birds show behavioral plasticity in response to perceived predation risk to reduce self-risk or risk to offspring, but (2) this plasticity incurs fitness-related costs. I experimentally increased the perceived risk of predation by enlarging the diameter of the nestbox entrance from the standard 3.2 cm to 5.0 cm once incubation began. Unexpectedly, large-hole females spent significantly less time being vigilant than small-hole (control) females during late incubation. Both males and females also exhibited plasticity with respect to their provisioning behavior. Experimental males increased provisioning visits and experimental females decreased provisioning visits with increasing brood size, whereas control males and females behaved similarly and were unaffected by brood size. Females did not show plasticity in their incubation or brooding behavior. Notwithstanding the behavioral plasticity revealed by increasing perceived predation risk, treatment had no effect on hatching success or early hatchling survival, and nor did it affect nestling body condition or fledging success. We conclude, therefore, that house wrens show behavioral plasticity in response to perceived predation risk, but that the fitness-related costs associated with this flexibility appear negligible.


Imported from ProQuest Dorset_ilstu_0092N_10650.pdf


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