Scaled quail (Callipepla squamata) were fed several dietary sources of estrogenic compounds to determine their effects on reproductive systems. In 1 experiment diethylstilbestrol (DES) (a potent synthetic estrogen) at daily doses of 0.5, 1.0, or 5.0 mg/bird/day dramatically increased (P 0.05) effects were observed with doses up to 10-fold greater of phytoestrogens (plantsource estrogens). Neither coumestrol (COUM) (the most potent reported phytoestrogen) nor Biochanin-A (Bio-A) (the most common phytoestrogen) resulted in any changes in ovary or oviduct weight in an avian bioassay system shown to be sensitive to a variety of estrogenic compounds. In a 2nd experiment 200 pairs of scaled quail were fed the phytoestrogens, morin (a flavone) and Bio-A (an isoflavone), as well as DES, for 8 weeks. Egg laying and fertility were depressed by 1.0 mg/bird/day DES. Fertility also was depressed by 10x that dosage of Bio-A, but egg laying was unaffected; morin had no effect on reproductive parameters. Since a dose of 10 mg/bird/day phytoestrogen is about 2 x the dose possible with maximum reported daily consumption of green vegetation, at maximum phytoestrogen concentrations reported in plants, it was concluded that dietary phytoestrogens played no significant role (either inhibitory or stimulatory) in reproductive success of scaled quail. J. WILDL. MANAGE. 51(1):198-201 For decades, biologists have observed that quail populations in the arid southwest vary radically from year to year due to fluctuations in their reproduction. Reproductive success has been shown to be primarily dependent upon the amount of rainfall during the late winter and spring (Lehmann 1953, Rosene 1969, Leopold 1977). Although variation in reproduction may be attributed directly to rainfall, it is usually indirectly attributed to the effect of rainfall on vegetation (MacGregor and Inlay 1951, Francis 1970). Estrogenic compounds (phytoestrogens) in moisture-stressed plants have been shown to affect the reproductive capabilities of some mammals (Labov 1977). Phytoestrogens contained in the green forage of annual plants were postulated to act as inhibitors of reproduction in California quail (Callipepla californica) during dry years (Leopold et al. 1976). The concentrations of these plant compounds were elevated in the contents of crop samples taken from quail collected during drought conditions. The principal phytoestrogens reported to cause reproductive difficulties in animals are the isoflavones, which are chemically related to flavonoid plant pigments, and coumestrol, a coumestan chemically more similar to animal estrogenic steroids. Four of the isoflavones (genistein, formononetin, Bio-A, and diadzein) have been isolated from pasture legumes and shown to have estrogenic activity (Shutt 1976). The responses of different animal species to various phytoestrogens may differ markedly due to differences in digestion; therefore, relative estrogenic potencies found in 1 study may not apply to all species (Bickoff et al. 1961). The physiological effects of phytoestrogens on avian reproduction has received little attention. Leopold (1977) concluded that his preliminary findings on the effects of phytoestrogens on quail reproduction were more suggestive than definitive and that a great deal of additional study would be required to fully understand these relationships. The objective of this paper is to determine the role, if any, of 3 dietary phytoestr gens on the reproductive success of scaled quail. The authors wish to thank the U.S. For. Serv., Rocky Mtn. For. and Range Exp. Stn. for providing partial funding for this study. We sincerely appreciate the gift of purified coumestrol from B. E. Knuckles, Proj. Leader, Nutr. Res. Unit, U.S. Agric. Res. Serv. West. Regional Res. Cent. The technical assistance of R. W. IPresent address: P.O. Box 3105, Sherman, TX 75090. 2 Present address: Poultry Science Department, North Carolina State University, Raleigh, NC 27695.