Reasons for Population Decline

​​​​​​​​​The reasons for the population decline of the Orange-bellied Parrot (OBP) are not clear. Past and ongoing habitat loss and degradation, particularly in the migration range in northwest Tasmania and the Bass Strait islands, and the wintering range in southeastern mainland Australia is believed to be one of the greatest threats to OBPs

Other known and potential threats to the OBP include:

  • loss of genetic diversity and inbreeding
  • disease
  • stochastic environmental events (e.g. drought)
  • climate change
  • predators (e.g. Foxes and Cats) and competitors (e.g. Goldfinch and Starlings)
  • barriers to migration and movement
  • hybridisation with Blue-winged Parrots.

Orange-bellied Parrot in its breeding range at Melaleuca. Photo: Col Rowe

Habitat degradation and fragmentation

It is likely that fragmentation and loss of the wintering habitat over the last 100 years could be a significant cause for the OBP population decline.

OBP habitat has been degraded and lost throughout its range, but much of this impact has occurred within the non-breeding range (i.e. migratory corridors and wintering areas) including: drainage of wetlands for grazing; alteration and destruction of saltmarsh for industrial and urban development; stock grazing of native vegetation; vegetation clearance for agricultural purposes; and disturbance through recreational activities (e.g. off-road vehicles). It also appears that the breeding range of the species has contracted. In recent years, few OBPs have been found outside the Melaleuca area where all known breeding now occurs and the causes of this contraction are not clear.

The decline in female breeding participation over recent years was possibly influenced by reduced female condition. While the causal links are not clear, the extended drought between 1997 and 2010 may have reduced the quality and availability of food resources at key sites on the mainland prior the breeding season. This may have been exacerbated by the lack of ecological burns in the Melaleuca area, which further reduced the quality, and availability of some food sources. Interactions with other species may have also influenced the contraction of the breeding range.

Predation

Although there is a lack of clear evidence that predation of OBPs by foxes and cats is a serious threat, anecdotal observations on the mainland suggest there is the potential. A fox has been observed stalking OBPs (L. Robinson pers. comm. in Orange-bellied Parrot Recovery Team 2014) and evidence of cat predation of a Blue-winged Parrot was observed at a site where OBPs were also seen (J. Starks pers. comm.iOrange-bellied Parrot Recovery Team 2014). Intuitively, the presence and high abundance of these introduced predators at OBP sites must increase the level of mortality and thus limit recovery potential.

There is also some evidence that sugar gliders may have killed three, but potentially six OBPs during translocations of the birds to Birchs Inlet between 1999 and 2005 (Holdsworth 2006).  Sugar Gliders (Petaurus breviceps) have not been recorded at Melaleuca.

Nest box competitiors and predators at Melaleuca recorded by a Scoutguard motion sensor camera. Photo: DPIPWE

Competition

The introduced European Rabbit (Oryctolagus cuniculus) grazes on saltmarsh and beach-dune vegetation and on weed species, though the impact this has on food availability for OBPs has not been assessed. In the breeding grounds, Common Starlings (Sturnus vulgaris) have aggressively prevented OBPs from entering known nest-hollows (Higgins 1999).

Feral Honeybees (Apis mellifera) are also known to invade and occupy tree hollows and nest boxes to the exclusion of OBPs. Sugar Gliders also compete for nest sites at Birchs Inlet.

Weed invasion of native vegetation has the potential to degrade potentially suitable OBP foraging habitat. The loss of large areas of saltmarsh to pasture has resulted in the spread of agricultural weeds, in places seriously degrading remnant saltmarsh communities (McMahon et al 1994). The introduced salt-tolerant Rice Grass (Spartina anglica) invades and out-competes saltmarsh vegetation such as Beaded Glasswort, potentially reducing available foraging habitat. In Tasmania, introduced Marram Grass (Ammophila arenaria) and Sea Spurge (Euphorbia paralias) are the subject of intensive eradication efforts within the Tasmanian Wilderness World Heritage Area. Both species are vigorous colonisers and out compete a range of native OBP food plants. The spread of sea spurge is also exacerbated by dune erosion caused by cattle grazing along coastal areas of the northwest and Bass Strait islands (i.e. areas used during migration).   

Beak and Feather Disease

Psittacine Beak and Feather Disease (PBFD) virus causes beak and feather abnormalities in parrots. In 2001 PBFD was listed as a key threat to at least 25 threatened Australian species or subspecies under the Environment Protection and Biodiversity Conservation Act 1999 (DEH 2005). This disease is also recognised as a threat in the National Recovery Plan for OBPs (OBPRT 2014). 

Infected parrots have potential to either succumb to disease, or recover and develop antibodies. There is also potential for clinically normal birds to shed virus periodically through their life. The virus is known to be present in many widespread and common parrot species, including sulphur-crested cockatoos, rainbow lorikeets and crimson rosellas, species that may have contact with the OBPs either at the single-OBP Melaleuca breeding site in the Tasmanian Wilderness World Heritage Area or their mainland wintering grounds (DEH 2005, Peters et al., 2014, Eastwood et al., 2015).

PBFD virus has also recently been found in green rosellas which co-occur with OBPs at Melaleuca. The existence of reservoirs for PBFD in wild parrots throughout the range of OBPs is therefore highly likely. Infected chicks typically become symptomatic as they undergo feather development, yet adults rarely become clinically affected (DEH 2005).​​


Cause of the 2014-15 PBFD virus outbreak

Over the past 30 years, PBFD has been confirmed at multiple times in both the captive and wild OBP population. 

Genotyping of the virus in the 2014-15 outbreak indicated that it was a likely to be a result of disease spillover/transmission from another parrot species in the wild, rather than from the captive bred release birds. Since the outbreak, in June 2015 an expert “Veterinary Technical Reference Group” (VTRG, a Working Group of the Recovery Team) was formed to provide timely expert advice in relation to OBP health, disease and biosecurity.

There has been preliminary work on the development of a PFBD virus vaccine. However, as it is unlikely that a vaccine will be available for some time, important management activities such as the release of captive-bred OBPs into the wild population will need to be considered without the aid of vaccination.


 

References

Predation

Holdsworth, M.C. 2006. Reproductive success and demography of the orange-bellied parrot Neophema chrysogaster. M Sc thesis, University of Tasmania, Hobart.

Competition
Higgins, P.J. (ed.) (1999). Handbook of Australian, New Zealand and Antarctic Birds. Volume Four - parrots to dollarbird. Melbourne: Oxford University Press.

McMahon, A.R.G., Race, G.J. and Carr, G.W. 1994. Vegetation survey and remote sensing of Victorian saltmarshes in relation to orange-bellied parrot Neophema chrysogaster habitat. Ecology Australia Pty Ltd.

Disease

Brown, P.B., Holdsworth, M.C. and Rounsevell, D.E. 1994. Captive breeding and release as a means of increasing the orange-bellied parrot population in the wild. Pp. 135-141 in Serena, M. (Ed.) 1995. Reintroduction Biology of Australian and New Zealand Fauna. Surrey Beatty, Chipping Norton.

DEH (2005). Threat Abatement Plan for Beak and Feather Disease affecting endangered psittacine species. Department of the Environment and Heritage, Canberra, ACT.

Eastwood, J.R., Berg M.L, Spolding, B., Buchanan K.L., Bennett, A., and K. Walder (2015). Prevalence of beak and feather disease virus in wild Platycercus elegans: comparison of three tissue types using a probe-based real-time qPCR test. Australian Journal of Zoology 63 pp. 1–8

Orange-bellied Parrot Recovery Team (2014). (Draft) National Recovery Plan for the Orange-bellied Parrot. Neophema chrysogaster. Department of Environment and Primary Industries, East Melbourne.

Peters, A., Patterson, E.I., Baker, B.G., Holdsworth, M., Sarker, S., Ghorashi, S.A. and S.R.Raidal (2014) Evidence of Psittacine beak and feather disease virus spillover into wild critically endangered orange-bellied parrots (Neophema chrysogaster). Journal of Wildlife Diseases 50: DOI: 10.7589/2013-05-121.


 

Contact

Orange-bellied Parrot Tasmanian Program
Natural Values Conservation Branch
GPO Box 44
Hobart TAS 7001

Email: OBP.Program@dpipwe.tas.gov.au

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