Abstract
Summary
1. Adolescent female ring doves (Streptopelia risoria) were injected with progesterone, estrogen or a combination of the two. Progesterone did not increase oviduct weights over the controls. Estrogen caused moderate increase, while the maximum increase was caused by synergism between estrogen and progesterone. 2. Eight-day priming with estrogen, followed by 2-day treatment with the estrogen-progesterone combination, caused oviduct growth as great as that caused by the 10-day treatment with the combined dose. On the other hand, priming with progesterone did not significantly augment the effect of 2-day treatment with the combination. 3. On the basis of these data and of a discussion of the mechanisms of nest-building and incubation behavior, it is suggested that the normal cycle includes a period of estrogen secretion (concurrent with nest-building) followed by progesterone secretion (associated with egg-laying maximal oviduct growth, and incubation behavior).
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