Causes of mortality in a nestling population of free-living hihi (stitchbird—Notiomystis cincta)

Abstract

The hihi is an endangered New Zealand species and its survival depends on the health of translocated populations. Low nestling survival was detected at Zealandia–Karori Sanctuary (KS) during the 2008–09 breeding season with 34% of eggs surviving to fledge. Samples obtained from live and dead hihi nestlings showed that several disease syndromes contributed to nestling deaths. Cause of death was diagnosed by necropsy and histopathology for 25 nestlings. Mortality was highest (60%) in nestlings ≤7 days old and was associated with seasonally low minimum daily temperatures (<11°C). Deaths in this age group were most commonly attributed to poor pulmonary aeration and starvation. Ventriculitis was associated with mortality in eight 6–19-day-old nestlings with no indication that weather was implicated. The remaining deaths were from a variety of unrelated events or causes. Candida albicans, Aspergillus sp. and an unidentified haemoparasite were found among the nestling population. There was no evidence of coccidia or other intestinal parasite infections. In contrast to translocated populations at other sites, nesting material recovered from nest boxes contained low densities of tropical fowl mites (Ornithonyssus bursa). To improve survival for nestlings up to 7 days old, extra food provisioning and nest box weather protection during inclement weather is suggested.