Norfolk boobook

Watercolour by James Stuart, 1839

The Norfolk boobook is very similar in appearance to the New Zealand and Tasmanian boobooks, being a small brown hawk owl with mottled plumage. It is smaller, darker and more reddish in colouring than the Tasmanian boobook, with much spotting.[6] However, it is slightly larger than the nominate subspecies from New Zealand; female boobooks are larger than the males, with New Zealand females comparable in size to Norfolk Island males, a factor which gave rise to sexing difficulties with hybrid birds in the conservation management program.[7]

The owl inhabits the island's subtropical rainforest, which was largely cleared in the 19th century following human settlement. Most of the remaining forest lies within the small (4.65 km²) Mt Pitt section of the Norfolk Island National Park.

The population of the Norfolk boobook declined with the clearance and modification of its forest habitat, especially the felling of large trees with suitable hollows for nesting in. There was also competition for nest hollows with feral honey bees and introduced crimson rosellas.[9] By 1986 the population had been reduced to a single female bird, named "Miamiti" after a matriarch of the Norfolk Island people.[10] As part of a program to attempt to conserve at least some of the genes of the insular subspecies, two male moreporks of the nominate New Zealand subspecies, Ninox novaeseelandiae novaeseelandiae, were introduced to the island as mates for the female. The males were sourced from the New Zealand subspecies rather than one of the Australian subspecies as it was discovered that it was more closely related to the Norfolk Island taxon.[11][12] Nest boxes were also provided. One of the introduced males disappeared a year after introduction but the other successfully mated with the female with the pair producing fledged chicks in 1989 and 1990. The original female disappeared in 1996 but, by then, there was a small hybrid population of about a dozen birds. These birds and their descendants continue to exist on the island. By 2018, between 45-50 birds were known, although the population has been inbred and aging with no new recruitment since 2012.[13]

The New Zealand and Norfolk boobooks are considered to be very closely related, with some debate over whether it should even be recognized as a separate taxon; they can only be distinguished by their physical features.[3] For this reason, the International Ornithological Congress does not consider this subspecies to be extinct as it was saved by the hybridization program, despite it no longer surviving as a genetically pure lineage. Genetic analysis indicates that half the nuclear genome and all the mtDNA of the original Norfolk boobook persists in the modern birds, marking it a special case of a taxon that can still be considered extant in a hybrid form. This may be due to the last surviving pure bird being a female, allowing for the mtDNA to be fully passed on.[4][5]

• Anon. (2004). What the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) means for Norfolk Island. Commonwealth of Australia. ISBN 0-642-55031-X
• Double, Michael; Olsen, Penny (1997). "Simplified polymerase chain reaction (PCR)-based sexing assists conservation of an endangered owl, the Norfolk Island Boobook Ninox novaeseelandiae undulata". Bird Conservation International. 7 (3): 283–286. doi:10.1017/S0959270900001581.
• Garnett, Stephen T.; & Crowley, Gabriel M. (2000). The Action Plan for Australian Birds 2000. Environment Australia: Canberra. ISBN 0-642-54683-5
• Higgins, P.J. (ed). (1999). Handbook of Australian, New Zealand and Antarctic Birds. Volume 4: Parrots to Dollarbird. Oxford University Press: Melbourne. ISBN 0-19-553071-3
• Norman, Janette; Olsen, Penny; Christidis, Les (1998). "Molecular genetics confirms taxonomic affinities of the endangered Norfolk Island Bookbook Owl Ninox novaeseelandiae undulata". Biological Conservation. 86 (1): 33–36. doi:10.1016/S0006-3207(98)00012-3.