The aim of this thesis is to show the direct changes in the physiology, morphology, and behavior of Japanese quail when administered with Testosterone-filled polymer microspheres. 36 experimental male quail were injected with either dispersion medium, testosterone microsphere resomer 1 (PLGA RG502 H; 4.4μg testosterone/100μl), or testosterone microsphere resomer 2 (PLGA RG503H; 4.4μg testosterone/100μl). Blood samples, behavior, food consumption, body mass, and cloacal gland sizes were collected from the birds throughout the next 12 experimental days that passed. The results indicate that the exogenous testosterone administered to Japanese quail did not elevate circulating hormone levels.