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Unformatted text preview: - Castration of young males eliminated sexual behaviors- Implantation of testes from same male or other males into the peritoneal cavity restored sexual behavior In later experiments, it became clear that testosterone is one of the primary hormones involved in this control of reproductive behavior.-When looking at a model of average testosterone levels in males over the course of the year, there are seasonal differences. Low during overwintering/migration and molt, high during the breeding season. If we focus on breeding season levels, we see a within-season pattern as well. Testosterone concentrations increase dramatically at the onset of the breeding season, and this is followed by increases in courtship and related aggressive activities. The same cycle can happen several times within the same breeding season, particularly when birds have more than one reproductive cycle per season. EUROPEAN STARLING EXAMPLE SONG SPARROW EXAMPLE...
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- Spring '09