Sex-Specific Hypothalamic-Pituitary-Gonadal Axis Sensitivity In Migrating Songbirds

Authors

Kristen M. Covino, Canisius CollegeFollow
Jodie M. Jawor, Canisius CollegeFollow
Sara R. Morris, Canisius CollegeFollow
Frank R. Moore, University of Southern MississippiFollow

Document Type

Article

Publication Date

1-1-2018

Department

Biological Sciences

School

Biological, Environmental, and Earth Sciences

Abstract

In seasonally migratory species, the overlap between the migratory and breeding life history stages is a balance between the physiological and behavioral requirements of each stage. Previous studies investigating the degree to which songbirds prepare for breeding during spring migration have focused on either circulating hormone levels or direct measures of gonadal recrudescence. In this study, we evaluated the phenology of breeding preparation in a long-distance migratory songbird, the Swainson's Thrush (Catharus ustulatus), by assessing hypothalamic-pituitary-gonadal (HPG) axis sensitivity with gonadotropin-releasing hormone (GnRH) bioassays throughout the migratory period. During spring migration both males and females had a significant response to GnRH injections as reflected in elevated testosterone levels. The magnitude of response to GnRH injections, R_potential, in females stayed consistent throughout spring migration; however, R_potential in males increased as the migratory season progressed. It is clear that at least some degree of endocrinological breeding development occurs either before or during spring migration in both sexes, however the phenology appears to be sex specific. In males this breeding development continues at a relatively steady pace throughout the migratory period while in females, relatively little endocrine breeding development occurs during migration. These sex-specific differences in the phenology of the endocrine breeding development warrant future investigations for both male and female songbirds. Moreover, research focused on how physiological breeding development is balanced with the expression of migratory traits in long-distance songbird migrants is needed.

Publication Title

Hormones and Behavior

Volume

97

First Page

112

Last Page

120

Recommended Citation

Covino, K. M., Jawor, J. M., Morris, S. R., Moore, F. R. (2018). Sex-Specific Hypothalamic-Pituitary-Gonadal Axis Sensitivity In Migrating Songbirds. Hormones and Behavior, 97, 112-120.
Available at: https://aquila.usm.edu/fac_pubs/15044