STUDIES ON THE PHYSIOLOGY OF REPRODUCTION IN BIRDS

Abstract

Under standard conditions in which the temperature factor would seem to be the chief seasonal variable, measurements were made of the age of attainment of sexual maturity (production of first egg) in 404 doves and 316 common pigeons belonging to 10 races. Within each of these races some [female][female] were reared from eggs laid in each month of the year, and a measure obtained of the influence of this varying season of origin upon age at maturity. Birds from eggs of Sept.-Jan., inclusive, matured earliest; those from other months at markedly older ages[long dash]36% older in pigeons and 52% older in doves. In general, pigeons mature at an earlier age than do ring doves. Different races within either of these species mature at unequal ages and thus reveal genetic factors, probably involving the anterior pituitary, which also condition the establishment of maturity. Under the most favorable conditions now known a dove or pigeon must be approximately 4 months old before it will produce an egg. If an age of 4-5 mos. is reached during the fall the maturity is delayed, if reached during Feb.-July maturity is hastened, by endocrine conditions (thyroid, perhaps pituitary) connected with this part of the year. The author''s earlier studies have shown that this season of accelerated maturity is also the season in which, even in mature birds, thyroid size and activity are decreasing. This rule probably applies to birds generally. A seasonal factor has been found in practically all aspects of sex and reproduction thus far studied in doves and pigeons.