No abstract

An important component of the restoration strategy for the critically endangered kaki or black stilt (Himantopus novaezelandiae) is captive breeding for release. Since 1981 1,879 eggs were collected from wild and captive pairs, with birds laying up to four clutches. Eggs were incubated artificially and most chicks reared by hand until released as juveniles (about 60 days) or sub-adults (9-10 months). Because survival in captivity is a significant determinant of the number of birds available for release, we wished to identify sources of variation in mortality to assess potential impacts of management on productivity. Hatchability was 78% for captive-laid eggs and 91% for wild-laid eggs. Survival of hatched eggs was 82% by 10 months of age for both wild and captive birds. Most egg mortality occurred early in incubation and around hatching: the timing of mortality was unaffected by whether birds were captive or wild, hybrid or pure kaki, or when eggs were laid. Heavier hatchlings showed higher initial survival, as did chicks from wild parents. Hatchlings from fourth-laid eggs showed lowest survival, even though hatchling mass tended to increase with hatch order. Survival of chicks subjected to major health interventions was 69% after 4 months. No differences in survival were found between different genders, hybrids and pure kaki, handreared or parent-reared birds, chicks hatching early or late in the season, different seasons, different-sized groups of chicks, chicks reared in different brooders, juveniles kept in different aviaries, and chicks from subsequent clutches. Birds subjected to minor health interventions were equally likely to survive as healthy

A significant increase in hatching and late-incubation deaths during two breeding seasons in a captive population of endangered black stilts (kaki, Himantopus novaezelandiae) prompted an investigation into the potential role of iodine deficiency. During the 1997 and 1998 breeding seasons, the survival rate of captive-laid eggs during artificial incubation and hatching was lower than that of eggs laid by wild kaki, which were collected and incubated artificially in the same environment. Necropsy results revealed abnormalities in thyroid structure. These abnormalities had been occurring in captive birds since 1994, but they peaked in 1997 and 1998 at 30% and 81%, respectively, of all diagnosed necropsies. Necropsies of pied stilts, hybrids, and one kaki from the wild revealed no thyroid abnormalities. Gross morphological symptoms observed at hatching in chicks that died were consistent with those described for iodine deficiency in poultry. Serum levels of thyroxine (T4) were considerably higher in wild pied stilts and hybrid chicks than in captive adult, subadult, and kaki chicks. In five individuals from the captive population, serum levels increased after about 160 days of iodine supplementation and approached values in the wild. The constraints associated with working with such a critically endangered species (e.g., small sample size and an urgent need to effect changes) precluded the use of an experimental approach to determine the role iodine deficiency played in peri-hatching deaths. However, we believe the evidence presented here strongly supports a case for the impact of iodine on survival within the captive population. Our experience also highlights the need for vigilance in captive programs with respect to potential dietary deficiencies when endangered species Grant sponsor: University of Otago.

A potential cause of pododermatitis ("bumblefoot") was investigated in captive-reared juvenile black stilts at the Department of Conservation "Kaki Recovery Program" at Twizel, New Zealand. To address the importance of substrate, the development of clinical signs in individuals was compared among aviaries that contained rubber matting and/or salt footbaths, and controls. No effect of either experimental manipulation of the environment was apparent on pododermatitis development. With the substrate appearing not to be an initiating factor, and a previous study that indicated that the birds' diet fulfills the nutritional requirements for rearing black stilts in captivity, results of this study suggest that insufficient space for exercise may instead be the cause.

It is recommended that pre-release anthelmintic treatment of black stilts should be used only if indicated by health screening. Any treatment should incorporate annual efficacy testing to monitor the emergence of anthelmintic resistance.