Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Vulnerable as Ninox natalis
Recovery Plan Decision Recovery Plan required, this species had a recovery plan in force at the time the legislation provided for the Minister to decide whether or not to have a recovery plan (19/2/2007).
 
Adopted/Made Recovery Plans National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan] as Ninox natalis.
 
Other EPBC Act Plans Threat Abatement Plan for Reduction in Impacts of Tramp Ants on Biodiversity in Australia and its Territories (Department of the Environment and Heritage (DEH), 2006p) [Threat Abatement Plan].
 
Threat abatement plan to reduce the impacts of exotic rodents on biodiversity on Australian offshore islands of less than 100 000 hectares 2009 (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2009u) [Threat Abatement Plan].
 
Policy Statements and Guidelines Survey Guidelines for Australia's Threatened Birds. EPBC Act survey guidelines 6.2 (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2010l) [Admin Guideline].
 
Information Sheets Final Report of the Christmas Island Expert Working Group to the Minister for the Environment Protection, Heritage and the Arts (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2010a) [Information Sheet].
 
Federal Register of
    Legislative Instruments
Declaration under s178, s181, and s183 of the Environment Protection and Biodiversity Conservation Act 1999 - List of threatened species, List of threatened ecological communities and List of threatening processes (Commonwealth of Australia, 2000) [Legislative Instrument] as Ninox natalis.
 
Non-statutory Listing Status
IUCN: Listed as Vulnerable (Global Status: IUCN Red List of Threatened Species: 2013.1 list)
NGO: Listed as Vulnerable (The Action Plan for Australian Birds 2010)
Scientific name Ninox natalis [66671]
Family Strigidae:Strigiformes:Aves:Chordata:Animalia
Species author Lister, 1889
Infraspecies author  
Reference  
Other names Ninox squampila natalis [26045]
Ninox squamipila natalis [26195]
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images

Scientific name: Ninox natalis

Common name: Christmas Island Hawk-Owl

The Christmas Island Hawk-Owl had previously been considered as a subspecies of N. squamipila (Norman et al. 1998).

The Christmas Island Hawk-Owl is about the size of a common pigeon (26 to 29 cm) but with a barred breast. It has an unmistakeable boo-book call. Unlike other raptors, including many owls, there is little difference in size between males and females with females being only slightly larger than the male. The Hawk-Owl is a small owl weighing approximately 140 to 210 g (Hill & Lill 1998b).

This species is confined to Christmas Island in the Indian Ocean. This species occupies permanent territories in all forest types on the island, with highest densities in primary forest and lowest in post-mining regrowth. These birds are absent from unregenerated mine sites (Hill 1997b; Hill & Lill 1998a).

Radio-tracking and territory mapping conducted in 1998 indicated that Hawk-Owls occupy essentially exclusive territories with an average area of approximately 18 ha. Hawk-Owls were widespread on the island in both primary and disturbed habitats (Hill & Lill 1998a).

Three types of territory mapping data were collected (1994). They include; simultaneous calling , territorial disputes and calling at dusk or dawn (all types were based on estimating the bird location by listening to owl calls (Hill & Lill 1998a).

Roosts have been located on Christmas Island by noting where an owl made its last call before dawn, then returning during the day to search for the owl. Roosting sites were also found by opportunistically following up distinctive calls (Hill & Lill 1998b).

The total number of breeding birds is estimated at 1200 (Garnett & Crowley 2000). However, some argue that the minimum total population size (in 1995) was less than 1000 mature individuals.

It is estimated that there are 562 ±105 occupied Hawk-Owl territories on Christmas Island (Hill & Lill 1998a).

Hill and Lill (1998a) estimated that the Island prior to settlement had a carrying capacity in the order of 740 ±135 owl territories. Gibson-Hill (1947) reported that owls were not rare and were widely distributed over the entire island. Between 1994 and 1996 Hill and Lill (1998a) estimated the population at 556 ±101 occupied owl territories in primary rainforest and 6 ±4 occupied owl territories in regrowth vegetation, and a total population size of 562 ±105 occupied territories.

The total Christmas Island Hawk-Owl population has probably decreased by at least 25% since settlement because approximately 25% of the forest has been cleared on the Island (Hill & Lill 1998a; Olsen & Stokes 1989).

The Hawk-Owl mainly inhabits dense rainforest on both plateau and coastal terraces of Christmas Island (Higgins 1999). On the plateau, it is found in tall closed evergreen forest with irregular canopy and numerous emergent trees, including Syzigium, Planchonella and Hernandia up to 40 m tall, and with an understorey of thickets consisting of Pandanus Palms Pandanus spp. (Gibson-Hill 1947; Hill 1996a; Hill & Lill 1998a).

On coastal terraces this species inhabits deciduous forests with canopy up to 30 m. It occurs in highly disturbed (formerly cleared) areas, with secondary growth of native and introduced trees, including Macaranga, Claoxylon, Leucaena and Muntingia, forming low (less than 10 m) closed forest; or in low herb lands with dense growths of ferns (Gibson-Hill 1947; Hill 1996a; Hill & Lill 1998a).

The species was once recorded in roadside shrubs next to disturbed secondary forest; and once in low weed-infested herb lands (Gibson-Hill 1947; Hill 1996; Hill & Lill 1998a). The Hawk-Owl generally avoids areas that have been cleared or are being rehabilitated (Hill 1996a; Hill & Lill 1998a).

Hawk-Owls choose to roost in the bottom third of the canopy of trees with particularly deep crowns, in areas with fewer low understorey and more mid-level understorey trees, suggesting a preference for sheltered, concealed, roost sites with easy escape routes below them (Hill & Lill 1998a).

The Hawk-Owls require undisturbed habitat for breeding (Kent & Boles 1984), although at least two breeding records are close to settled areas (Hill 1996a). This species has been recorded breeding in hollows in Syzigium nervosum within primary forests. Breeding does not occur in secondary growth because trees there are not old enough to have developed hollows (Hill 1996a). This species roosts in both closed forest and secondary growth with dense understorey, usually in middle layers of vegetation, 5-15 m above ground (Hill 1996a; Hill & Lill 1998a). However, this species has also been recorded roosting in rainforest canopy (Phillips et al. 1991).

Owls select roost sites that are sheltered from above which provides them with protection from heavy rain and sun (Hill & Lill 1998a).

All four nests recorded for this species, three in marginal rainforest and one in primary rainforest, have been in tree hollows in Syzygium nervosum. Syzygium nervosum is, therefore, a very important tree species for Christmas Island Hawk-Owls and if its abundance was to change in the future, this might lead to a shortage of nest sites (Hill & Young 1995).

Little is known about the breeding system for this species (Hill 1996a; Hill & Young 1995). The breeding season appears to be contracted, with breeding recorded in all quarters of the year. Chicks possibly tend to fledge July to December, though fledged dependent young have been noted in April, May and August to December (Hill 1996a; Hill & Young 1995; Olsen & Stokes 1989).

The Hawk-Owl probably breeds annually. It is likely to have long-term monogamous pair-bonds. Age at first breeding is not known, but it is probably capable of breeding at approximately 12 months. All three nests studied were in hollows of large emergent Syzygium nervosum. No nest material was used. The Hawk-Owl is likely to have a maximum of two eggs in a clutch. The length of incubation period is not known. Incubation is apparently by the female only, which leaves the nest briefly to be fed by the male (Hill 1996a; Young & Hill 1995).

Chicks appear to be brooded only by the female, but both parents appear to feed young. The fledging period is 68-77 days. Fledglings are dependent on parents for 2.5 months after leaving nest and possibly stay in the natal area for some time after that. No information is available about breeding success. The Hawk-Owl possibly desert nests after heavy rains or if disturbed by people (Hill 1996a; Young & Hill 1995).

The generation length for this species is 10 years (Garnett & Crowley 2000).

The average area of an Owl territory is approximately 18 ha (Hill & Lill 1998a).

The Hawk-Owl feeds mainly on large insects and sometimes on small vertebrates (Higgins 1999). It is nocturnal, feeding mainly in the understorey of primary forest, or in secondary vegetation along roadsides (Hill & Lill 1998b), and in disturbed areas around human settlements (Kent & Boles 1984). In forest, this species forages mainly by perch-hunting. It searches for prey while moving from one perch to another. When prey is located, the Hawk-Owl usually swoops onto the outer foliage or trunk of shrubs or small trees, sally-strikes prey, then flies back to a new perch. Prey is snatched from heights of 2 to 7 m (Hill & Lill 1998b; Olsen & Stokes 1989; Phillips et al. 1991). It is likely that the Hawk-Owl hunts in the upper layers of the forest as it is better lit than the dark understory, indicating that light levels maybe important in determining the feeding success of the species (Hill & Lill 1998b).

The Hawk-Owl is also seen hunting along roadsides, repeatedly flying from perch to perch (30-100 m), and spending long periods watching from each perch (approximately 15 minutes) inspecting road for prey (Hill & Lill 1998b). It also sallies for insects attracted to street lights around settlements, particularly during August to September (Olsen & Stokes 1989).

An analysis of regurgitated pellets, stomach samples and faeces showed the owls to be primarily insectivorous, eating a wide variety of medium to large insects, especially Orthoptera, Lepidoptera and Coleoptera. The Hawk-Owl is also known to eat the gryllacridid cricket, Gryllacris rufovaria, the only member of this family of tree crickets recorded on Christmas island. The Hawk-Owl supplements this diet with vertebrates of which introduced Black Rats, Rattus rattus were the most important, as well as native and introduced geckos and white-eye Zosterops natalis (Hill & Lill 1998b).

This species is sedentary. A radio-tracking study during the breeding season in May to September indicated that males ranged over areas of 5.3-13 ha (n=5) and females 6-7 ha (n=2), almost entirely within the range of its mate. There is no information on movements at other times of year or dispersal of young (Higgins 1999).

Hawk-Owls rarely stay at one roost site for more than two successive days. They have numerous roost sites which they use only once and a small number which they use a number of times (Hill & Lill 1998b).

Studies indicate that the Hawk-Owl leaves its roost at about sunset and returns to roost at dawn. Owls were not seen to change roosts during the day except when they were disturbed. Owls normally roost alone or with their mate (Hill & Lill 1998b).

The standard method for censusing Owls is to playback the owls in order to elicit a reply (Hill & Lill 1998a).

The greatest current threat to the Hawk-Owl is from the introduced Yellow Crazy Ant Anoplolepis gracilipes. These ants may prey directly on nestlings and, by killing the dominant life-form, the Red Crab Gecaroidea natalis, and by encouraging scale insects which in turn cause tree dieback, may alter the whole ecology of the island (O'Dowd et al. 1999).

After spreading slowly, this pest occupied approximately 15-18% of the island in 1999 (D. Slip pers. comm., in Garnett & Crowley 2000) and affected some 2500 hectares, 25% of the total forest area. Although aerial baiting between 2001 and 2003 was successful in reducing numbers of Crazy Ants dramatically (DEH 2003), there are still about 400 ha of infested forest that will need continued management (D. Slip 2003, pers. comm.).

Forest clearance, which is no longer permitted, has destroyed 25% of the species' habitat (Garnett & Crowley 2000).

There is a small risk of avian disease, for which the exotic Java Sparrow Lonchura oryzivora and Tree Sparrow Passer montanus could act as reservoirs (Hill 1997b).

The Christmas Island Rainforest Rehabilitation Program has been replanting an average of 10 ha/yr of previously cleared and mined land since 1989 (R. Hart cited in Hill & Lill 1998a). As rehabilitated forest gets older and more structurally complex, its value as owl habitat is likely to increase (once it reaches an age at which potential nest hollows form) (Hill & Lill 1998a).

Other outlined recovery actions include negotiating with all landowners to ensure protection of primary forests outside the national park; a review of the Christmas Island Quarantine Service; conducting a community education program; rainforest rehabilitation of priority minefields, and controlling the abundance and spread of Yellow Crazy Ant. Pending control, there is a need to establish a captive population of the Hawk-Owl with the aim of reintroduction (DEH 2003).

The national recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill 2004b) has been developed to guide threat abatement strategies.

The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

Threat Class Threatening Species References
Climate Change and Severe Weather:Climate Change and Severe Weather:Climate change altering atmosphere/hydrosphere temperatures, rainfall patterns and/or frequency of severe weather events National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Energy Production and Mining:Mining and Quarrying:Habitat destruction, disturbance and/or modification due to mining activities National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or habitat degradation by weeds National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Felis catus (Cat, House Cat, Domestic Cat) National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Anoplolepis gracilipes (Yellow Crazy Ant, Gramang Ant, Long-legged Ant, Maldive Ant) National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive and Other Problematic Species and Genes:Presence of pathogens and resulting disease National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Residential and Commercial Development:Residential and Commercial Development:Habitat modification (clearance and degradation) due to urban development National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].
Transportation and Service Corridors:Roads and Railroads:Vehicle related mortality National recovery plan for the Christmas Island Hawk-Owl Ninox natalis (Hill, R., 2004b) [Recovery Plan].

Department of the Environment and Heritage (DEH) (2003). Christmas Island National Park - Yellow Crazy Ants. [Online]. Australian Government Department of the Environment & Heritage, Canberra. Available from: http://www.environment.gov.au/parks/christmas/fauna/crazy.html.

Garnett, S.T. & G.M. Crowley (2000). The Action Plan for Australian Birds 2000. [Online]. Canberra, ACT: Environment Australia and Birds Australia. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/action/birds2000/index.html.

Gibson-Hill, C.A. (1947). Notes on the birds of Christmas Island. Bulletin of the Raffles Museum. 18:87-165.

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

Hill, F.A.R. (1996a). The Christmas Island Hawk-Owl: its distribution, an estimate of density, population size and its conservation status. Report to Australian Nature Conservation Agency. RAOU, Melbourne.

Hill, F.A.R. (1997b). The Christmas Island Hawk-Owl Ninox natalis Recovery Plan. Birds Australia, Melbourne.

Hill, F.A.R. & Lill, A. (1998a). Density and total population estimates for the threatened Christmas Island Hawk-Owl Ninox natalis. Emu. 98:209-220.

Hill, F.A.R. & Lill, A. (1998b). Diet and roost site characteristics of the Christmas Island Hawk-Owl Ninox natalis. Emu. 98:227-223.

Hill, R. (2004b). National recovery plan for the Christmas Island Hawk-Owl Ninox natalis. [Online]. Department of the Environment and Heritage. Canberra, Commonwealth of Australia. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/recovery/n-natalis/index.html.

Hill, R. & Young, J. (1995). Searching for nests of the Christmas Island Hawk Owl Ninox squamipila natalis. Unpublished report to Australian Nature Conservation Agency.

Kent, D.S. & Boles, W.E. (1984). Corella. 8:93-94.

Norman, J.A., L. Christidis, M. Westerman & F.A.R. Hill (1998). Molecular data confirms the species status of the Christmas Island Hawk-Owl Ninox natalis. Emu. 98:197-208.

O'Dowd, D.J., P.T. Green, & P.S. Lake (1999). Status, impact and recommendations for research and management of exotic invasive ants in Christmas Island National Park. Centre for Analysis and Management of Biological Invasions, Monash University.

Olsen, P.D. & Stokes, T. (1989). The state of knowledge of the Christmas Island Hawk-Owl Ninox squamipila natalis. In: R.G. Meyburg and R.D. Chancellor, eds. Raptors in the Modern World. WWGBP, Berlin.

Phillips, D.J., Olsen, P.D., Rentz, D.C.F. & Lawrence, J. (1991). Observations on the diet of the Christmas Island Hawk-Owl Ninox squamipila natalis. Emu. 91:250-251.

Slip, D. (2003). Personal Communication.

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This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

Citation: Department of the Environment (2014). Ninox natalis in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Tue, 30 Sep 2014 23:43:30 +1000.