A QUANTITATIVE EXAMINATION OF OVARIAN GROWTH IN THE WHITE-CROWNED SPARROW

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Abstract
Ovarian development in Zonotrichia leucophrys grambelii subjected to long daily photoperiods of constant duration is a logarithmic function of time until a weight of approximately 50 m is attained. Although there is a slight non-photo-periodic ovarian growth, especially in 1st-yr. birds, long daily photoperiods are essential for normal ovarian growth and constitute the essential environmental information used in the control of the ovarian cycle. The photoperiodic control mechanism in the female differs from that of the male in that the logarithmic growth phase brings the ovary to only approximately 10% of its maximum weight whereas the logarithmic growth phase of the testis brings it to about 50% of maximum weight. Complete ovarian development occurs only very rarely in captive birds. Until an ovarian weight of approximately 50 mg is attained the gonado-tropin content of the anterior pituitary of the female in captivity appears to be similar to that of photostimulated males; beyond this time that of the female is significantly lower.