Article

Journal of Chemical Ecology

, Volume 37, Issue 12, pp 1349-1357

Role of Testosterone in Stimulating Seasonal Changes in a Potential Avian Chemosignal

  • Danielle J. WhittakerAffiliated withBEACON Center for the Study of Evolution in Action, Michigan State UniversityDepartment of Biology, Indiana University Email author 
  • , Helena A. SoiniAffiliated withInstitute for Pheromone Research and Department of Chemistry, Indiana University
  • , Nicole M. GerlachAffiliated withDepartment of Biology, Indiana University
  • , Amanda L. PostoAffiliated withInstitute for Pheromone Research and Department of Chemistry, Indiana University
  • , Milos V. NovotnyAffiliated withInstitute for Pheromone Research and Department of Chemistry, Indiana University
  • , Ellen D. KettersonAffiliated withDepartment of Biology, Indiana University

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Abstract

Songbird preen oil contains volatile and semivolatile compounds that may contain information about species, sex, individual identity, and season. We examined the relationship between testosterone (T) and the amounts of preen oil volatile and semivolatile compounds in wild and captive dark-eyed juncos (Junco hyemalis). In wild males and females, we observed an increase in volatile compound relative concentration early in the breeding season. This increase mirrored previously described seasonal elevation in T levels in wild males and females, suggesting a positive relationship between hormone levels and preen gland secretions, and a possible role for these secretions in signaling receptivity. In females, the greatest relative concentrations of most compounds were observed close to egg laying, a time when steroid hormones are high and also the only time that females respond to an injection of gonadotropin-releasing hormone with a short-term increase in T. In a study of captive juncos held on short days, we asked whether the seasonal increases observed in the wild could be induced with experimental elevation of T alone. We found that exogenous T stimulated the production of some volatile compounds in non-breeding individuals of both sexes. However, of the 15 compounds known to increase during the breeding season, only four showed an increase in relative concentration in birds that received T implants. Our results suggest that testosterone levels likely interact with other seasonally induced physiological changes to affect volatile compound amounts in preen oil.

Key Words

Testosterone Chemical communication Chemical signals Birds Dark-eyed junco Passerine Steroid hormones Preen gland