The Reproductive Endocrinology of Fiordland Crested Penguins Eudyptes pachyrhynchus

Abstract

Plasma concentrations of progesterone (males and females), 17α-hydroxyprogesterone (males and females), oestradiol (females) and testosterone (males) were measured in Fiordland Crested Penguins at different stages from courtship to late in the incubation period. Plasma levels of oestradiol and testosterone were high during courtship, had declined to low levels by the time eggs were laid, and remained low in incubating birds. Progesterone was also highest during courtship in both males and females, but remained at relatively high levels following egg laying and during incubation. However, males returning from foraging towards the end of the incubation period had significantly elevated testosterone levels and lowered progesterone levels. Plasma levels of 17α-hydroxyprogesterone remained constant in both sexes through all stages of the breeding cycle examined here.