Limb growth and development in the endangered, captive reared, black stilt (Himantopus novaezelandiae) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Turitea, Palmerston North, New Zealand

Abstract

Captive management is a crucial part of the conservation of one of New Zealand's endemic and critically endangered wading birds, the black still (Himantopus novaezelandiae). Acquired limb deformities have become apparent in captive reared black stilt, highlighting a lack of knowledge of normal limb growth and maturation. Body weight, and tarsus, carpal and remex length were measured on stilts on ad libitum and restricted fed diets. It was found that body weight, and carpal and remex length was significantly slowed by food restriction. Male stilts did not fully compensate in subsequent growth, whereas female stilts compensated in subsequent growth to greater than that of females previously on ad libitum diets. Food restriction also significantly increased the percentage of time stilts spent foraging and interacting with each other. Bone histology was undertaken on the tarsus and first phalanx of the wing. This data, combined with the morphological measurements enabled the identification of the critical growth periods, in which black stilt are most likely to develop limb abnormalities. These periods include: the first three weeks of age for leg abnormalities and between 13-25 days of age for wing abnormalities. The manganese (Mn) concentration in black stilt bone and feathers was also investigated. Key findings were that stilts with acquired limb deformities were not deficient in Mn, and feather Mn did not correlate with bone Mn concentration, and therefore can not be used as a non-invasive technique to monitor Mn bioavailability in the black stilt. The cause of angel wing and slipped tendon in captive reared black stilt was not resolved by the research. A Mn deficiency was eliminated but it is still uncertain whether rapid growth rates may have contributed to the abnormalities. This research has shown that dietary restriction in the early growth phase can be used to limit growth rates of black stilt, although the effects of this restriction on long term growth show sex-dependent differences. Further research into the incidence of limb abnormalities in the black stilt is encouraged, with the aim of contributing to the recovery of the critically endangered, wild population.