The endocrine basis of deferred sexual maturity in the wandering albatross, Diomedea exulans. L.

1 Earlier work with albatrosses led to the hypothesis that a critical element influencing ovarian development each year is whether the ovary responds to rising gonadotrophin secretion by secreting progesterone or oestradiol. In the former case no vitellogenesis occurs, the ovary does not mature and no egg-laying occurs. In the latter case ovarian growth and ovulation occurs. This `switch' between progesterone and oestradiol secretion may be important not only for the breeding frequency of adult birds but also prepubertally, influencing the onset of sexual maturity. This paper tests some of the underlying endocrine responses experimentally using known-age (4-11 years old) wandering albatrosses, Diomedea exulans L., at South Georgia. 2 Experiments using birds before and after bouts of sexual display discounted the possibility that high progesterone levels were an artefact of behavioural interaction. 3 Examination of the pituitary-ovarian axis, by injection of ovine luteinizing hormone (LII) and LH-releasing hormone, confirmed that the ovary does secrete progesterone, and that only progesterone is produced in immatures, unlike breeding birds in which oestradiol is also secreted. 4 In terms of endocrine status, female D. exulans were divisible into three main groups: younger (7 years) and last-time non-breeders. These categories were consistent with behavioural data from the same population. Thus the earliest age of breeding is 7 years, display rates increase after `physiological maturity' is attained but decrease once stable pairs are formed and attendance ashore prior to maturity does not influence the time taken to start breeding.


Publication status:
Authors: Hector, J.A.L., Pickering, S.P.C., Croxall, J.P., Follett, B.K.

1 January, 1990
Functional Ecology / 4
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