TESTOSTERONE AFFECTS THE ACOUSTIC STRUCTURE OF THE MALE CALL IN THE GREY PARTRIDGE (PERDIX PERDIX)

The effects of testosterone (T) on the acoustic features of the ''rusty-gate'' call of the grey partridge, a non-oscine bird, were studied in 24 males kept in semi-natural conditions. Half of them were implanted subcutaneously with T propionate in Silastic tubes at 10 weeks of age, the remaining were sham operated as controls. After one month implanted males showed significantly higher T levels than controls, while treatment did not affect body size. Individual recordings of calls were analysed and accurate measurements were taken by a digital spectrograph. The duration of calls was significantly greater in T-males than in controls. A similar lengthening has been described in nature in spring, when plasma levels of androgens rise. The frequencies of the most intense portion of the call ranged more widely and had a lower minimum in T-males than in controls, suggesting an hormonal control on call system at the peripheral/central level. In conclusion T affects specific temporal and frequency features of the male calls. The relationship between T and call structure could enable females to assess quality and sexual motivation of their potential mates.