A 9-year retrospective mortality review of captive orange-bellied parrots (Neophema chrysogaster) in Australia.

The orange-bellied parrot (Neophema chrysogaster) (OBP) is a critically endangered migratory parrot found in south-eastern Australia. A long-standing conservation recovery programme includes monitoring and support of the wild population and a multi-site captive insurance population. While disease represents a threatening process to the OBP, minimal information about causes of mortality in this species has been published. A systematic review of necropsy reports from the captive OBP metapopulation over a 9-year period (2010-2019) was undertaken to quantify and analyse the causes of mortality of captive OBPs. Infectious disease was the most common cause of death (35%), including respiratory aspergillosis and a range of bacterial infections, followed by trauma (7%). Confirmed or suspected Psittacine Beak and Feather Disease caused few deaths overall (1.4%) but caused an outbreak of juvenile and subadult mortality at one facility in 2019. Necropsy records alone were insufficient to determine the contribution of this infection to captive population health beyond these cases. Disease occurrence varied with site and age class; in particular, aspergillosis and mycobacteriosis were each more common at two separate sites, offering opportunities for further investigation of disease risk factors that could include environmental, husbandry and pathogen factors. A high proportion of cases (46%) could not be assigned a cause of death, though diagnostic success increased with age class, year of study and when histology was performed in younger age classes. These findings are relevant to future conservation decisions for the OBP, particularly resource allocation for research and diagnostics, and have broader interest to veterinarians, pathologists, ecologists and captive management specialists. Our findings also reinforce the importance of consistency in necropsy investigations and pathological terminology and the need for accessible and standardised mortality records for conservation programmes.