The reproductive cycles of the British and Continental races of the Starling (Sturnus vulgaris L.)

摘要: Accounts are given of the detailed structure reproductive systems male and female starlings (Sturnus vulgaris L.). It is shown that there differences between sedentary British starling migratory Continental bird in seasonal variations these systems. The gonads first-year begin to grow February, but rate growth greater than Continental. adult do not regress so far summer as those birds, they start precociously early autumn. until January or time when gonad birds accelerated. In February March much more rapidly birds. These degrees regression times rates reflected accessory sexual organs. males rete testis vas deferens show signs autumn, although other organs, apparently requiring a higher sex-hormone secretion, their earlier faster organs oviduct enlarges some individuals various Wolffian system also growth. apparent ovary autumn secretes both sex hormones, amount hormone secreted by different very variable. secondary characters either permanent vary according state cycle. browner colour iris yellowish distinguishing characters, and, addition, throat breast feathers narrower pointed same age. beak varying character. Owing secretion testes ovaries turns from dark grey yellow during this season. No similar change beaks noted February. When yellow, base mandibles feature male. behaviour races was studied, it found that, coincident with showed close attachment nesting sites. habit roosting nest-holes seen all year round race, becomes almost universal January. country, none described case which remain on Continent. At end actively growing, sing, northward migration commences, Continent interest sites first reported. question relation several aspects activity hormones discussed. evident two distinct live together Isles winter, cycles must be inherent dictated environmental variations. physiological species subspecies discussed, basis paper, proposed rename race Sturnus britannicus.