STUDIES ON THE PHYSIOLOGY OF REPRODUCTION IN BIRDS

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Abstract
Serum Ca was used as a measure of the relation of the parathyroids to reproduction. Male and female doves and pigeons were studied in 13 stages of the reproductive cycle. In these stages no measurable changes were found in the males (9.1 mgm. per 100 cc). Females, however, regularly show a great increase of Ca (to 20 mgm.) at each ovulation period. This increase begins about 123 hours before the beginning of deposition of shell and is coincident with changes in ovary, oviduct, adrenals and blood sugar earlier described. A relationship of the parathyroids to reproduction in birds is thus established. Female pigeons withstand without adverse effect, hypercalcemia in excess of that thought by Collip and co-workers to cause death in dogs. The evidence found in the literature for Ca changes in menstruation, pregnancy, lactation and menopause is discussed. The data obtained on pigeons further indicate seasonal changes in the blood Ca; highest values were found in summer when the gonads are largest and the thyroids smallest. Insufficient and inconclusive data were obtained on the question of a purely sex difference in the blood Ca during non-ovulation stages. The study is also a contribution to a knowledge of the mechanisms by which forced or crowded reproduction affects sexuality and sex ratios in pigeons; since, under these conditions, it is found that mobilization of Ca is maintained at an abnormally high level.

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