The concentration of plasma testosterone was studied in a number of territorial male Red-backed Shrikes, Lanius collurio, during a breeding season in the Italian Pre-AJps. Testosterone levels were highest at the time of the birds’ arrival and declined abruptly after a few days. This indicates that high levels of circulating testosterone are needed to sustain aggressive motivation while much lower levels may be sufficient for sexual behaviour in this species. Moreover, it also appears that males of Red-backed Shrikes have very high testosterone blood levels well before they gain their breeding sites.
- Breeding season
- Red-backed Shrike
ASJC Scopus subject areas
- Animal Science and Zoology
- Ecology, Evolution, Behavior and Systematics