The fluttering shearwater is relatively common, yet surprisingly little is known about the state of its population. Photo / Edin Whitehead
Desperately clinging to a handful of shallow scrapes and sandbanks on windy beaches, the NZ fairy tern represents what James Russell calls a "quintessential species conservation problem".
That this tiny, delicate species somehow hasn't been shunted into oblivion is remarkable.
Russell, a University of Auckland conservation biologist, feels the effort to save New Zealand's most threatened bird – with a population of just 40 – has been left tragically too late.
Last season, only six pairs attempted to nest at their storm-exposed coastal habitats near Auckland and Whangarei, even with the careful oversight of a Department of Conservation-led recovery programme.
The terns faced multiple threats, none of which were straightforward to resolve.
"Removing any one threat may have turned the species around when the population was larger and more resilient, but now they all need to be resolved at once because even a single chance event – like a big storm or rogue predator - could extinguish them once and for all from New Zealand," he said.
"We want to make sure we don't let our other seabird species fall in this situation, but sadly, many are heading that way."
Indeed, the fairy tern symbolised the unseen plight of seabirds in northern New Zealand, described in a major review published today.
The Northern New Zealand Seabird Trust's just-released report found that, dramatically, up to 90 per cent of populations in what was a global seabird hotspot were now at risk of extinction.
The region is a breeding ground for some 28 species, with five of them – the NZ fairy tern, black petrel, pycroft's petrel, Buller's shearwater and NZ storm petrel - found nowhere else on the planet.
"Being a massive island archipelago in the Pacific Ocean, and so close to the rich feeding grounds of the subantarctic convergence, New Zealand is a magnet for seabirds," Russell, a co-author of the review, explained.
"The Hauraki Gulf is dotted with islands among historically rich feeding grounds which are home to many seabird species, so many know that northern New Zealand has one of the highest breeding seabird species counts in the world."
Their traversing of marine and terrestrial environments by crossing back and forth from land to sea was one of the most important trans-boundary ecological linkages that scientists know of.
Its strongest impact was probably the natural fertilisation of land with marine nutrients.
The loss of seabirds thus had immediate downstream consequences on the natural world below and above water.
Yet learning more about how they were faring in the face of mounting odds had been "exceptionally" challenging.
"At sea it's only recently that we have been able to study their biology through the use of miniaturised tracking devices," he said.
On land they still tended to be somewhat inaccessible, returning at night or nesting on cliffs or underground.
"This makes it really challenging to accurately count and monitor their populations to determine if we are just seeing year to year variation, or symptoms of a longer-term decline," he said.
"So to some extent, they have been out of sight and out of mind, and we have hopefully assumed that they have avoided the worst of our human impacts - but sadly that no longer appears to be, indeed nor has it ever been, the case."
The review's lead author, University of Auckland doctoral student Edin Whitehead, said before a baseline could be put in place to conserve the birds, scientists first had to understand the specific threats stacked against them.
The report, released at the Birds New Zealand conference in Wellington this weekend, listed six of them – with "rapid action" needed to tackle all.
PREDATORS
As most seabirds weren't well adapted to moving in land environments, this put them at risk of a danger they didn't have to deal with until historically recently: mammal predators.
Because they had low reproductive rates and tended to nest on the ground, for long periods, they were particularly vulnerable to attack – and just one could have catastrophic consequences.
The incursion of one single stoat on tidal islands at Bethells Beach near Auckland wiped out around 70 Northern common diving petrels.
Other menaces included dogs, rats, pigs, hedgehogs and cats – which posed the extra threat of targeting both adults and chicks.
At these vital habitats on the mainland, constant trapping efforts during the breeding season were needed.
While many islands in northern New Zealand had been cleared of pests, they were still a problem on larger islands like Great Barrier Island – home to the world's largest population of black petrels, and one of only two remaining breeding sites for what was once a widespread species.
The review found the pressure of pests might be eased by more public awareness, and the country's nationwide Predator Free 2050 movement.
But, in the meantime, it called for continued biosecurity, a pest purge on Great Barrier Island, early detection technology on island strongholds, and even efforts to stop weed species from hurting seabird colonies.
FISHING
Anyone who's seen a shag dive for their freshly-hooked snapper would know seabirds can easily become accidental casualties of fishing.
Fishing by-catch – particularly with wide-ranging pelagic foragers such as albatrosses and large burrowing petrels – has been well-documented as a big driver of seabird loss.
Higher numbers of adult deaths drove declines across entire seabird populations, given that year-to-year survival rates of adults was normally high.
And, during breeding seasons, the death of a single adult bird from a pair could result in the death of their dependent chick, which couldn't be supported by a lone parent.
More widely, by-catch could unintentionally impact birds of certain ages and sex, driving damaging population skews.
The fishing industry had attempted to lessen its impact through strategies like line-weighting, night-setting, tori lines.
However, the report noted that, with not enough independent by-catch observers aboard fishing vessels, the level compliance with mitigation measures was tough to assess.
It found the observer coverage in Northland and Hauraki's commercial surface longline, trawl bottom longline fisheries had been markedly low – in the case of the latter, merely an average two per cent of hooks were observed.
Black petrels were the species most at risk of by-catch – and its vulnerable population couldn't sustain the rate of currently observed captures, which were potentially an under-estimate.
The review acknowledged it wasn't just commercial boats posing a problem: recreational fishers, too, could snag and kill birds like petrels and shearwaters as they chased baits underwater or tangled themselves in lines.
And the true toll of set-netting – known to catch diving seabirds, with shearwaters, diving petrels, penguins and shags most at risk – wasn't clear because commercial operations weren't observed, and only large incidents among recreational set-netters were recorded.
The report called for new fisheries exclusion zones during breeding seasons of affected seabirds, and expanded marine protected areas around key breeding sites.
POLLUTION
The threat of plastic to marine life isn't new – as far back as the late 1970s, one study documented 40,000 pieces per metre at beaches near main centre.
Yet frighteningly little has been done about it since.
As many plastics float in the marine environment, they were visible and available to seabirds, many of which happened to be opportunistic feeders.
As well as direct consumption by misdirected feeding behaviours, plastics were also ingested accidentally while feeding - or consumed by prey species in turn eaten by seabirds.
Ingested plastic often meant a slow, painful death for seabirds: it caused internal blockages and perforations, and could even result in gradual starvation by filling digestive tracts.
Not only was there physical harm from plastic concerning for seabirds, but potential toxicological effects that might be less immediately obvious.
In their manufacture, plastics were imbued with certain additives, such as PCBs, plasticisers and colourants that can have deleterious effects on organisms, such as inhibiting reproductive systems and causing developmental problems.
Smaller fragments, like notorious microplastics, meanwhile had greater surface areas and thus greater potential to pick up chemicals from the environment.
The waters around New Zealand are predicted to have the highest impacts from plastics on seabirds due to the diversity and abundance of seabird species, both native and migrant, that foraged here.
Alarmingly, plastics had been found in the carcasses of seabirds on one of the most remote islands in our archipelago, Campbell Island.
"With such a density and diversity of seabirds breeding close to New Zealand's largest city and most heavily populated area, the potential for impacts from plastic pollution are much greater," the report found.
Further, the semi-enclosed nature of the Hauraki Gulf in which they foraged meant plastics might accumulate at greater concentrations.
The report also noted the threat of oil spills – 2011's Rena disaster claimed at least several thousand seabirds, but the toll would be far more devastating if something similar happened in the Hauraki Gulf – and run-off from coastal development.
Even light pollution from cities and ships could severely affect seabirds, by disorienting them at night and causing them to crash-land.
The review suggested pollution problems could be addressed through litter capture devices, support for clean-up activities and restricting light from ships and urban areas that posed a high risk.
DISEASE
While there had been little research on disease in the region's seabirds, the review found it nonetheless posed a big risk.
An outbreak of avian cholera, for instance, could prove "disastrous" – particularly for those seabirds with small population sizes or restricted breeding sites.
Avian malaria could threaten little blue penguins, as could toxic dinoflagellate blooms, which have been implicated in mass deaths of yellow-eyed penguins in Otago.
But potentially the greatest disease threat was from contact with humans – especially researchers working on multiple islands and species.
"Maintaining strict quarantine measures between island visits and sterilizing equipment between use on different species should curb any negative impacts while the potential for disease transferral remains unknown," the report said.
"Without knowledge of what diseases may be present currently in native populations, we are unable to assess the risks from exotic or domestic species."
CLIMATE CHANGE
The speed and weight of climate change – and its wide-ranging influences on ocean temperature, currents and food sources - may prove too much for some seabirds to adapt to.
More powerful and more frequent storms, combined with higher sea levels, had the potential to destroy large amounts of nesting and roosting habitat for seabirds such as terns and gulls.
The fairy tern, for instance, was at risk of losing its entire breeding habitat to storm surges, as wash-outs already occurred during storm events.
Other species nesting on shell banks, like Caspian terns and black-billed gulls, were similarly at risk of losing habitats as well.
If such events unfolded during breeding seasons, they were likely to cause death - which for fairy terns, could spell near-extinction of the sub-species.
The review found climate change would hit seabirds both directly and indirectly, potentially affecting entire ecosystems, altering primary productivity and thus changing trophic relationships among species.
Changes in climate could even affect the functional traits of seabirds - which in turn could alter demographic rates and change population trends – as well as drive shifts in their ranges and prey.
"How different seabirds will respond to climate and ecosystem changes is related to many factors including their range, foraging behaviour and diet composition, nesting habitat, and life history characteristics," the review said.
"Some characteristics may facilitate adaptation whereas others will limit it. In short, some seabird species may fare well in a warming, and more acidic ocean conditions; others may become locally or globally extinct."
The report recommended establishing new colonies of some highly vulnerable species as insurance against catastrophic events, and gaining a better understanding of what shifts seabirds might undertake as their environment changed.
DISTURBANCE
Many seabirds spent most of their lives well out of sight of most people – even those of us who lived near breeding grounds.
Yet people and their pets could often still harm them, especially when recreational areas overlapped with roosting sites.
On top of that, urban development in coastal areas placed immense pressure on seabird populations, by taking away feeding, roosting and breeding habitats for seabirds such as gulls, terns, and shags – or bringing predators like cats and rats closer to colonies.
Simply just visiting places where seabirds were breeding could lead to burrows being trampled, forcing birds to leave their nests and abandon chicks to predators.
The report singled out the danger of off-roading on beaches, where nesting birds were often camouflaged against the sand, along with boats speeding through resting and feeding flocks.
It called for better planning regulations for coastal developments, like restricting cat
ownership and dog owners, and protecting some key habitats altogether.
'WE CAN'T WAIT'
A glaring issue was knowledge gaps about the region's seabirds.
"Some seabird species we have really only just discovered, such as the New Zealand storm petrel breeding on Te Hauturu-o-Toi/Little Barrier Island," report co-author Chris Gaskin said.
"It's quite possible that if the eradication of rats and cats on the island had not happened, we may never have known they were there."
But Russell added that the situation was too pressing to wait for research to catch up.
"It may take 10 or more years to build up an accurate picture of the trajectory of some seabird species, and so we recommend focusing directly on the threats themselves, where they can be locally addressed," he said.
"Mitigating any of the threats outlined can only have positive impacts on the state of our seabird species, and has the benefit of helping many of them at once, since they all seem to share the same threats."
Department of Conservation seabird scientist Graeme Taylor said there was increasing evidence to show the six threats highlighted in the report were real.
He agreed there was a troubling dearth of data.
"Compared with a lot of other groups, we are certainly behind in knowledge. When it comes to those most endangered species, we've got some of that data – but when you get into the more common species, it's very hard to get good information," Taylor said.
"We've got birds like fluttering shearwaters that are relatively common – yet we hardly know where they breed, what sort of numbers are in their breeding sites, and whether impacts out on the ocean, like climate change, have been affecting them."
Taylor pointed out that New Zealand was a major breeding seabird centre for the world and, above that, was home to a range of endemic species that could only be conserved here.
"A lot of these birds are some of rarest in the world, and we are doing as much as we can to stop them going extinct," he said.
"That means we are putting resources into those birds that are right on the edge – but it also means that a lot of the more common species haven't had a lot of attention, simply because we haven't had the resources to target at them.
"As this report points out, we do have to start throwing a lot more resources at those common species as well."
• New Zealand fairy tern (nationally critical)
• Black-billed gull (nationally critical)
• New Zealand storm petrel (nationally vulnerable)
• Caspian tern (nationally vulnerable)
• Black petrel (nationally vulnerable)
• Flesh-footed shearwater (nationally vulnerable)
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