Graduation Term


Document Type


Degree Name

Master of Science (MS)


School of Biological Sciences

Committee Chair

Pirmin Nietlisbach


Some species produce two broods in a season to maximize reproductive success; however, in species such as the house wren (Troglodytes aedon), not all individuals produce a second brood. We completed a cross-fostering experiment and examined the effects of individual characteristics on the probability of producing a second brood using breeding records from a long-term dataset. There was little evidence that the individual traits we examined affected the production of a second brood. However, the production of a second brood was significantly repeatable, indicating that individual characteristics have a substantial effect on the likelihood of producing a second brood. Eggshell coloration may also be indicative of female oxidative balance because protoporphyrin, a pro-oxidant, is found in red-brown eggshell pigmentation. We tested whether there is an association between eggshell coloration caused by protoporphyrin and antioxidant gene expression, heat shock protein gene expression and protein oxidative damage. Females with high levels of eggshell protoporphyrin had low HSPA8 expression and high levels of protein oxidative damage, a result consistent with the ‘poor-quality’ hypothesis that high levels of eggshell protoporphyrin are associated with poor oxidative balance. A prior study on the same population showed females with higher eggshell protoporphyrin content were older and produced high-quality offspring. This seemly paradoxical outcome is, however, consistent with the terminal investment hypothesis, that individuals with low residual reproductive value should maximize their investment in current reproduction.


Page Count


Available for download on Sunday, May 31, 2026