A well-intentioned but ill-informed decision led to the deaths of nine rare kiwi in September.
The Motuara Island rowi were being treated for a type of worm at Wellington Zoo when they developed aspergillosis, a condition that damages the lungs and is caused by a fungus found in bark and leaf litter.
Eight of the rowi at Wellington Zoo died in September, and a ninth in early October. A 10th died at Massey University, but of an unrelated condition.
Documents released under the Official Information Act show that the 2011 Brown Kiwi Husbandry Manual specifically advises that shredded bark should not be used to house kiwi, because of the risk of infection.
An email was sent out to all captive brown kiwi holders after the deaths with a "gentle reminder" that the birds "not be held on woodchip/wood bark substrate because of the increased risk of aspergillus spores in such".
Wellington Zoo spokeswoman Amy Hughes said the vet team, which worked in consultation with Department of Conservation staff, did not know of the risk at the time.
The team had tried to reduce the stress levels of the rowi by creating a natural environment for them, she said, but had they consulted the zoo's bird husbandry staff, they might have been told of the risk.
"This incident was unusual, and unfortunately comes down to a well-intentioned human error.
"Housing animals on bark does not always lead to respiratory illness, as it depends on the spores being in the bark chip. However, in future we will always err on the side of caution, and not use bark chip."
She said all the staff involved were devastated by the incident, and had gone through a rigorous internal debrief and put measures in place to ensure it did not happen again.
DOC conservation services manager Jo Macpherson said the DOC team did not have any concerns at the time about housing the kiwi on bark, and what happened was very unusual.
The risk of using bark was not known to the staff involved, who usually worked with wild birds, but it would be well understood by those who cared for captive animals, she said.
The kiwi husbandry manual had since been circulated to vets at Auckland Zoo, Massey University and Wellington Zoo, and to DOC staff who worked with rowi and tokoeka, the southern brown kiwi.
"We have all learnt from this, while at the same time recognise that everyone had the very best of intentions," Macpherson said.
Massey University associate professor Brett Gartrell said the fungal spores were found in all types of leaf litter and bark, but levels of aspergillus were usually low and did not cause any harm.
"However, there are occasions when the fungus proliferates in this material, which can result in serious disease.
"This has been seen before on kiwi with all types of substrate, including bark chip and leaf litter," he said.
National Kiwi Recovery Group leader Avi Holzapfel said kiwi management was complex, and different expertise and knowledge was needed in different environments.
Although the risk of infection from aspergillus spores in bark would have been well-known for those working with captive kiwi, it may not have been common knowledge among veterinary staff.
"Captive staff would have picked this up, most likely. Vet staff didn't think about it, didn't know about it, and may not have thought in that situation of checking. So that has been remedied, and that is the biggest learning . . . to actually look at the resources we've got."
Kiwi would usually be held on towels while at the vet, he said.
Rowi were the most intensely managed of the five kiwi species, "and with that intensive management comes a risk - so now and then things will go wrong.
"All of us are really concerned that this has happened, don't want to see this happen again, but in the context of the recovery of rowi, it is a small setback, not a big setback."
