Testosterone, reproductive stage, and territorial behavior of male and female European stonechats Saxicola torquata.
We investigated territorial behavior and circulating testosterone (T) levels in a multiple-brooded population of the European stonechat, a socially monogamous passerine bird with biparental care. Between arrival at and departure from the breeding territories, we (1) quantified behavior of both sexes in response to a simulated territorial intrusion (STI) of a male conspecific and (2) measured plasma T concentrations in males and females. Male response scores to a STI and male T concentrations varied with phase, but there was no temporal association between plasma T levels and the intensity of territorial behavior. During both two sexual and two parental phases, at least half of the tested males showed aggressive responses. About 20% of the tested males responded with courtship prior to laying of the first clutch, but none of the males courted during later phases. Age had a positive overall effect on male plasma T. Females also reacted to the STI of a male, but their responses did not vary with breeding phase. Female plasma T varied with phase, being elevated during production of the first but not of the second clutch. As with males, female responses to the STI were not correlated with T levels. Responses of pair partners were positively correlated with each other. We conclude that modulation of male territorial aggression with breeding phase is not regulated by changes of plasma T concentrations. In light of other studies showing reduced male aggression by pharmacological inhibition of cellular actions of T, we propose that T is permissive for male territorial aggression, but does not mediate short-term changes associated with breeding phase. The function of the high female plasma T concentrations during formation of first clutches could be related to the production of eggs with high concentrations of androgens.
Schwabl
Hubert
H
Center for Reproductive Biology, School of Biological Sciences, Washington State University, Pullman, WA 99164, USA. huschwabl@wsu.edu
Flinks
Heiner
H
Gwinner
Eberhard
E
D000367:Age Factors; D000818:Animals; D005260:Female; D008297:Male; D008425:Maternal Behavior / Q000502:physiology; D010152:Pair Bond; D010332:Paternal Behavior; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D012737:Sex Factors; D020308:Songbirds / Q000502:physiology*; D013731:Territoriality; D013739:Testosterone / Q000097:blood*
D013739:Testosterone