Estimation of gonadal and adrenal activities in birds by analyzing fecal steroid hormones

To estimate gonadal and adrenocortical endocrine activities of birds without disturbing them, we have devised methods for extracting and measuring steroid hormones in excreted feces. Methods needed for proper extraction of steroid hormones differed among species and included a simple extraction with water, an extraction with ethanol-acetone followed by an LH-20 column chromatography or an extraction with ether followed by a reverse phase HPLC. Samples thus prepared were analyzed for steroid hormones by radioimmunoassays. Preliminary experiments using Japanese quail showed that fecal steroid levels reflect plasma levels and hence the endocrine activity as well. Based on this experience, we proceeded to examine reproductive capacities of Japanese crested ibis, an endangered species with only one male and female were surviving in Japan in 1995, and also to study seasonal changes in gonadal and adrenocortical activities of wild rock ptarmigan. Clear changes in sex steroids and corticosterone were observed in the rock ptarmigan.