Gonadesiklus van die kroonkiewiet <i>Vanellus coronatus</i> op enkele binnelandse lughawens

Abstract

Ondersoek is ingestel na die gonadesiklus van 474 kroonkiewiete Vanellus coronatus wat gedurende 1986/87 op twee binnelandse lughawens versamel is. Geoordeel aan die ovariummassa en deursnit van die grootste sigbare follikel vind ’n opvallende aktiwiteitspiek in die ovariumsiklus van wyfies gedurende die voorsomer plaas. Geoordeel aan die massa, volume, histologiese ontwikkelingstadia en saadbuisdeursnit van die testes kom ’n ooreenstemmende maar langer aktiwiteitspiek ook by mannetjies voor. Hoewel die testes van onvolwasse mannetjies oor die algemeen kleiner is as dié van volwassenes, is sommige individue binne hul eerste lewensjaar potensieel tot voortplanting in staat. Klaarblyklik word die broeisiklus van die kroonkiewiet in ’n groter mate deur die relatiewe beskikbaarheid van voedsel as omgewingsfaktore soos daglengte, temperatuur of reënval beïnvloed.

English Title: Gonadal cycle of the crowned plover Vanellus coronatus at two inland airports

English Abstract

Gonadal cycle of the crowned plover Vanellus coronatus at two inland airports. The gonadal cycle of 474 crowned plovers Vanellus coronatus collected from two inland airports during 1986/87 was investigated. Judged by the ovarian mass and the diameter of the largest visible follicle, a prominent activity peak occurs in the ovarian cycle of females during early summer. Judged by the mass, volume, histological development stages and diameter jof the seminiferous tubules of the testes, a corresponding but longer activity peak also occurs among males. Although the testes of immature males are generally smaller than those of adults, some individuals are potentially capable of reproduction within their first year of life. Evidently the breeding cycle of the crowned plover is influenced to a greater extent by the relative availability of food than by environmental factors such as day length, temperature or rainfall.