Populations of the Toki, or Japanese Crested Ibis Nipponia nippon are now reduced to a single female in Japan, and captive and free-living populations of about 80 individuals in Yang Xian, Shaanxi Province and the Beijing Zoo, People's Republic of China. Very little has been published about the biology of this species except for Japanese journals and popular articles. Here we outline some unique aspects of the breeding biology of this species as well as introduce endocrine methods as a way of determining the source of reproductive problems in captive breeding programmes and, tentatively, how hormone manipulations based on these observations may help to enhance reproductive output. The Toki has a unique nuptial plumage that is acquired by the cosmetic application of a black tar-like substance secreted by a well-defined patch of skin in the throat and neck region. Apparent specialized down feathers develop in this region during a localized moult in November. The tar-like substance is secreted in January and February and is applied to the head, neck and upper torso by a combination of bathing and daubing behaviour. Development of nuptial colour is thus a combination of morphological development, secretion and a unique behaviour. This combination is found only in adults. Single plasma samples collected from captive Toki at known times in the breeding cycle suggest normal hormone patterns in some individuals, and abnormal levels in those that fail to breed. These conclusions are strengthened by endocrine investigations of a non-endangered ibis species, Threskiomis melanocephalus, that reveal normal patterns of circulating concentrations of gonadotrophins and sex steroids as expected for a seasonally breeding bird. Measurement of faecal hormone levels may be a less invasive way of monitoring reproductive function in critically endangered species. Recent work on Japanese Quail Coturnix japonica shows that hormone therapy using purified avian gonadotrophins in non-reproductive individuals results in gonadal maturation, egg-laying and production of reproductively active offspring. Although these techniques are still in their formative stages, results to date strongly suggest that carefully applied endocrine techniques can indicate potential problems in captive breeding programmes and may be useful for hormone therapy in critically endangered species.
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