Extrapair fertilizations (EPFs) are an important component of many socially monogamous mating systems. However, information about the reproductive tactics used by male and female birds in extrapair mating systems is still rare. We used radiotelemetry to measure territory use, forays, and mate association in Wood Thrush (Hylocichla mustelina) when females were fertile and not fertile. We also conducted paternity analysis to determine the frequency of EPFs in our study population. Socially paired male and female Wood Thrush maintained a close physical association while on their own territory. Most of the off-territory forays observed during the fertile stage were conducted by social pairs. Lone males rarely engaged in off-territory forays during their mate's fertile period but made relatively frequent off-territory forays when their mates were not fertile. Male Wood Thrush may trade-off investment into paternity assurance and extrapair tactics by favoring a mate-guarding tactic when their within-pair paternity is most at risk. The overall rate of EPF (6%) exhibited by Wood Thrush is low compared with other synchronously breeding avian species. We suggest that extensive on- and off-territory mate association throughout the females' fertile period may limit female extrapair mating opportunities and also limit a male's ability to interact with any soliciting extrapair females.

Excursiones Hacia Afuera del Territorio y Sistema Genético de Apareamiento de Hylocichla mustelina