Meeting Abstract

27.3  Friday, Jan. 4  Polyandrous female house wrens increase the size, but not immunocompetence, of their extra-pair young FORSMAN, AM*; VOGEL, LA; SAKALUK, SK; JOHNSON, LS; MASTERS, BS; JOHNSON, BG; THOMPSON, CF; Cornell University; Illinois State University; Illinois State University; Towson University; Towson University; Towson University; Illinois State University amf226@cornell.edu

Extra-pair fertilizations (EPFs) occur in many socially monogamous birds, but it is unclear how females benefit in cases where they receive no direct material benefits from extra-pair mates. We tested the hypothesis that female house wrens (Troglodytes aedon) seek EPFs to secure indirect genetic benefits for their young. We predicted that extra-pair young (EPY) would have higher body condition and greater immunocompetence than their half-sibling brood mates, within-pair young (WPY). We assessed three components of nestling immunocompetence: cutaneous immune activity, humoral immunity, and plasma bactericidal activity (i.e., innate immunity). WPY had higher cutaneous immune activity than their EPY brood-mates in two of the three years of our study. EPY and WPY did not differ in measures of innate and humoral immunity. WPY also had higher albumin/gamma-globulin than EPY, but, they were not in better condition based on other measures. EPY had consistently longer tarsi than their WPY half-siblings. These results are inconsistent with the hypothesis that females gain indirect genetic benefits by engaging in extra-pair matings, at least in the form of enhanced immunocompetence or condition of EPY. Females may, however, benefit indirectly through the increased structural size of EPY, but this hypothesis awaits further study.