“What’s in a name?”, poses the famous Shakespearean query. “A lot” would be the answer regarding the Norfolk Island boobook owl. Some would say this distinctive subspecies found only on Norfolk Island became extinct sometime in the late 1990s. But then what’s been making those tell-tale ‘boobook’ sounds?
The Norfolk Island boobook owl, its taxonomic name, Ninox novaeseelandiae undulata, evolved on Norfolk amidst the type of dense forest Captain James Cook would have discovered in 1774. Towering pines, palms and broad hardwoods covered virtually the entire island. These natural conditions helped shape the Norfolk boobook’s comparatively shorter, rounder wings and longer tail feathers, making it better suited to manoeuvre through the thick woody canopy. With an abundance of tree hollows in which to make a nest and nothing above it in the food chain, the owl must have existed in considerable numbers across every peak and valley. Human settlement since 1788 rapidly changed that landscape. It’s estimated by the 1900s up to three-quarters of the native forest had been cleared for agriculture and most of the remaining older trees, the boobook’s favoured nesting site, would be logged over the following decades. No small wonder that their numbers declined to where a collector permitted to shoot six owls for various museums in 1912 notes in his log his difficulty in locating specimens. (This rarity wasn’t helped by his taking 24 owls more than his permit allowed, with another seven taken 13 years later for another collection.)
With the continuing loss of nesting sites, as well as the introduction and self-introduction of competitors, predators (cats and rats), and perhaps inadvertently the effects of pesticides, by the mid-20th century Boobooks had become scarce. Indeed, although Islanders would occasionally hear an owl in the vicinity of Mt. Pitt, an intensive search by the Australian Parks and Wildlife Service in 1985 didn’t record a single sighting. It was against this urgent apprehension that ornithologist, Dr. Penny Olsen, now of the Australian National University, and four colleagues arrived in 1986 to try again. They found one owl, a female which the locals named “Maimiti” after Fletcher Christian’s wife, and never a second. By the end of this field work would occur the creeping realisation that not only was Miamiti rare, she was the last of her kind; the rarest owl in the world. The focus and importance of their work immediately changed. How do you save a type of bird doomed to extinction?
The Norfolk Island bookook owl is, or was, considered a distinct subspecies of the New Zealand morepork owl, Ninox novaeseelandiae. Individual owls are commonly called a Boobook in Australia and a Morepork in New Zealand, and both terms are heard on Norfolk Island. I’m opting for the one more commonly used in the literature. The two are different birds separated by time and geography, but the thought was they were closely-related enough that two male New Zealand moreporks were introduced into the Norfolk forest in 1987. This was a bit of a punt. No one knew Maimiti’s age and whether she was still able to breed. No one knew if the introduced males would survive in the new environment. Fortunately the owls weren’t aware of these concerns and Maimiti mates with one of them, thereafter named ‘Tintoela’, the Norfolk Island word for sweetheart.
An interesting backstory to a programme in which everything mattered was the decision taken early to allow breeding to occur in the wild, rather than in captivity. Both has its risks, but the view was leaving Miamiti in her native forest would minimise impact to her behaviour and any resulting offspring, if breeding were successful. An egg laid in 1988 broke, but a chick hatched in 1989 and the first successful breeding by the second generation took place in 1993. By 1995, there were 11 members of this new population, still found only on Norfolk Island. And some 20 years after Maimiti was last observed in 1996, in November-December, 2016, an Island-wide survey reported 32 owls: 8 pairs, 13 single birds and one group of three in clusters distributed over much of the Island. This is a sub-species taken from the brink, but what are they and how are they faring? Is the Norfolk Island boobook owl extinct? And is the resulting population, so to speak, out of the woods?
The Norfolk Island boobook owl that Cook might have seen and described in detail by ornithologist, Gregory Mathews, in 1912 no longer exists. What exists now on Norfolk and nowhere else is a hybrid, and science – with its desire for order and classification – has serious physical, and I suppose administrative issues, with hybrids.
Although occasionally occurring in the wild, hybridisation is frowned upon and for a host of reasons. It may result in the introduction of genes that can adversely affect behaviour and fitness (and in keeping with ‘the exception is the rule’, it can also increase genetic fitness). But as much as anything, hybridisation complicates taxonomy – that branch of biology that attempts to identify and name species by their ‘unique’ characteristics. Hybridisation by definition renders a species’ gene pool less unique and identifiable. It is one of the conditions that the International Union for Conservation of Nature (IUCN) considers can lead to extinction. In fact, a specific IUCN guideline states that if the entire population is hybrid, the species can be considered extinct. For largely that reason, the Norfolk Island boobook owl was declared extinct in the Action Plan for Australian Birds 2000. But again, so what’s that sound we sometimes hear at night? The owl certainly exists and is steadily increasing its range.
Dr. Olsen and others have since argued that the Norfolk boobook represents a special exception to the ‘extinction by hybridisation’ rule. Usually when interbreeding occurs it involves multiple members of both sexes. But the Norfolk hybrid population is the result of a single male and a single female, so half of the original gene pool and all of the original mitochondrial DNA, a key factor, still resides in this population. And whereas hybridisation is usually an ongoing process which progressively alters the original genetic makeup over time, the Norfolk population derives from a single genetic introduction, never repeated. They concluded that the Norfolk Island boobook owl, as a subspecies, continues to live, but in hybrid form. The science community evidently was listening. The Action Plan for Australian Birds 2010 no longer listed the Norfolk Island boobook owl as extinct, but as Critically Endangered. It is.
The Norfolk Island owl population is still quite small and as such is highly vulnerable to impact and change. The banding of each young fledgling and the opportunity for individual examination that occurred through the 1990s and periodically for perhaps a decade thereafter provided detailed information of the early population. Much, however, is still not known.
In the beginning, there was a decided shortage of males. This had some fairly obvious implications for population growth, but this disparity was expected to eventually even itself out. In addition, because identifying an owl’s sex is not easy from afar – females are typically larger, but a physical inspection is required – we don’t know 20 years later if this exceptional bias towards females has been corrected and what would ordinarily be a reasonable rate of growth. Similarly, because researchers are still trying to determine an owl’s natural territorial range in the present-day Norfolk Island environment, no one can approximate how many owls by now there ought to be. The survey estimate of 32 individuals in 2016 is considerably less than the numbers projected in 1996 and part of the effort is to better understand why. Our knowledge is literally as new as this hybrid. Nonetheless, science has a new taxonomic name: Ninox novaeseelandiae undulata/novaeseelandiae. With thanks to the scientists and the many locals who enabled this to happen, and to Maimiti and Tintoela, this is its own happy ending.
So how shall we conclude this extraordinary tale? As we began, with Shakespeare’s reply to his own question. “What’s in a name?” Does it really matter? “A rose by any other name would still smell as sweet”. Oh, what a remarkable bird.
Image Credit: Stephen Gardiner
Article content disclaimer: Article first published in Discover Norfolk, Volume 01 Issue 01, 2017. Please note that details of specific travel, accommodation and touring options may be outdated. References to people, places and businesses, including operating days and times may be have changed. References to Government structure and Government businesses/entities may no longer be applicable. Please check directly with businesses and/or Government websites directly rather than relying on any information contained in this article before you make travel arrangements.