The ability of eight species of birds to produce precipitins was studied. Two species which responded weakly or failed to respond to the precipitinogen, were further injected in an attempt to produce agglutinins or antihormones. The owl, pheasant and partridge were classified as good precipitin producers, but average and maximum titers were well below those given by the chicken which constantly yields excellent precipitating antisera. A few individual owl and pheasant antisera showed definite in vitro titer increases similar to those regularly shown by chicken antisera upon standing under refrigeration. The majority of the antisera, however, failed to show changes in their original titers. The ducks and turkeys yielded antisera with very low precipitin titers and several animals failed to respond at all. In addition, no antihormone activity could be shown in the turkeys injected with gonadotrophin hormone. No precipitins could be demonstrated in any of the guinea fowl and pigeon antisera, but slightly enhanced agglutinating reactions over that of normal guinea fowl were secured by injection. The implications of these results are discussed.