Sexually selected vigilance behaviour of the grey partridge is affected by plasma androgen levels

In the grey partridge, Perdix perdix, vigilance and calling activity are two sex-dimorphic behaviours that are critical for mate choice. To ascertain whether circulating levels of testosterone directly affect vigilance (i.e. the occurrence of upright alert posture), we compared vigilance scores of testosterone-implanted versus control males both during the normal activity of the flock and after the passage of a raptor silhouette; in the latter case, the calling activity was also recorded. Hormone-treated males were more vigilant than controls in both experimental situations. Vigilance was correlated with calling rate. Testosterone seems to act as a link, relating conspicuous behaviours involved in sexual selection to male quality and physical condition, because of the costs of having high levels of both signalling and androgens. (C) 1997 The Association for the Study of Animal Behaviour.