Abstract
Introduced mammalian predators and anthropogenic habitat modification have resulted in the loss of 62 avian species since humans arrived in New Zealand. The conservation paradigm for New Zealand relies upon predator free, ecologically intact or restored islands to serve as sanctuaries and breeding sites for a range of threatened species. Island breeding programs and translocations to restore native fauna to the mainland and other off-shore sites, introduce specific risks related to disease spread.
Beak and Feather Disease Vims (BFDV), was found in clinically affected juvenile Red Crowned Parakeet (RCP, Cyanoramphus novaezelandiae) on Hautum Island in 2008. This finding had major implications for conservation management of parrots in New Zealand, including the critically endangered kakapo (Strigops habroptilus) and orange fronted parakeet (Cyanoramphus malherbi). Feather loss had also been reported in RCP on nearby Tiritiri Matangi Island, suspected to be caused by BFDV. BFDV is endemic in the exotic Eastern rosella (Platycercus eximius) and Sulphur-crested cockatoo (Cacatua galerita) on the North Island of New Zealand. A spill over event likely spread the vims to RCP on nearby islands in the Hauraki Gulf of the Auckland region.
Four cross-sectional surveys were conducted between 201 1-2012 on Tiritiri Matangi Island to determine the presence, prevalence and seasonal trends of key diseases of parrots that may result in feather loss. A total of 184 birds were captured in mist nets. All birds were anaesthetised to collect samples of blood, feathers and faeces, and in 2012 a skin biopsy from the head was included. Individuals were examined for general condition including stages of moult and body weight, and morphometrics and standardised photos were obtained. Hippoboscid flies were collected opportunistically when observed on birds. Blood and feather samples were tested for BFDV by PCR, and a subset of samples was tested for the presence of antibodies to BFDV using the haemagglutination inhibition test. Skin was processed routinely for histopathology and examined under light microscopy for evidence of BFDV as well as other causes of feather loss. The prevalence of feather loss in the study population changed substantially during the 2 year project, from 0% (95%CI: 0-6.7%) in April 2011, up to 45% (95%CI: 32.0-58.5%) in September 2012. This feather loss was predominantly around the head and neck region, with varying degrees of hyperkeratosis and lichenification evident on physical exam. BFDV was detected only in the first sampling session at 4% prevalence (95%CI: 0.5-13.0%), and was not correlated with clinical signs. A mite was detected in skin biopsies of all birds showing signs of feather loss and, increasingly, in skin biopsies from birds not showing changes to feathering. Examination of hippoboscid flies revealed female mites and eggs on the abdomen.
The characteristic feather loss associated with this mite has been observed in other populations of RCP, as well as in several populations of the orange fronted parakeet. Continued monitoring of the study population is recommended to broaden our understanding of the factors that underpin the host-parasite relationship, and produce survival data to infer the impacts of this parasite on viability at individual and population scales.