Meeting Abstract
P1.153 Tuesday, Jan. 4 Testosterone, plumage coloration and extra-pair paternity in North American barn swallows EIKENAAR, C*; WHITHAM, M; KOMDEUR, J; VAN DER VELDE, M; MOORE, I.T.; Virginia Tech, Blacksburg; Virginia Tech, Blacksburg; Rijks Universiteit Groningen; Rijks Universiteit Groningen; Virginia Tech, Blacksburg eikenaar@vt.edu
In most monogamous bird species in which males care for young, circulating testosterone concentration in males peaks during territory establishment and around the social female’s fertile period. The variation in the height of peak testosterone concentration between males may have a considerable impact on individual fitness. For example, exogenous testosterone has been shown to enhance behaviors important for social and extra-pair mate choice. However, little is known about the relationship between natural male testosterone concentrations, sexual signals, and individual reproductive success. To investigate these relationships we measured sexual signals and male testosterone concentration, and determined within and extra-pair fertilization success in North American barn swallows (Hirundo rustica erythrogaster). Dark rusty colored males had higher testosterone concentrations than drab males. Extra-pair paternity was common (42% of young), but neither within- nor extra-pair fertilization success was related to male testosterone concentration. Within-pair fertilization success was positively related to male ventral plumage color, with dark rusty colored males being less often cuckolded than drab males. Dark males did not, however, have higher extra-pair fertilization success than drab males. Our study is the first to relate natural male testosterone concentration to within and extra-pair fertilization success. Our findings suggest that in North American barn swallows, male testosterone concentration does not play a significant direct role in female mate choice and sexual selection. We provide a potential explanation for the relationships among male testosterone concentration, ventral plumage coloration, and within- and extra-pair fertilization success.
