Edin Whitehead

The life and times of Shag 224796

Kawau tikitiki, spotted shags, are a little bit special. In the Hauraki Gulf, they’re genetically unique and highly endangered. Auckland Museum senior researcher Matt Rayner has spent the last few years trying to figure out how to stop them disappearing entirely.

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Shag 224796 got her GPS backpack in September 2023, a couple of months after her face turned bright green and the ring around her eyes went from grey to turquoise. Disco season.

Up until Christmas Eve, her life was pretty ordinary. Over spring, she clocked up hundreds of dives a day, mostly at the mussel farm in the Firth of Thames, commuting back and forth between there and her nest on Tarahiki/Shag Island to feed her chicks. Tarahiki is a jumble of rocks off the eastern coast of Waiheke Island, and it’s pretty much the only shag colony left in the Hauraki Gulf.

Once her chicks left the nest, Shag 224796 wasn’t quite as busy as before. She didn’t have extra mouths to feed, and it wasn’t yet high summer, when the lower Firth heats up and life in it diminishes. By night, she’d roost on the cliffs of Wekarua Island, at the mouth of Manaia Harbour at the eastern side of the Firth, as still as a figurine. By day, she’d fish, diving again and again, stopping to rest in the bays along the Coromandel coast. In a month, she and the other kawau would abandon the Firth and move north.

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“What made you pick a catchy name like 224796?” I ask Matt Rayner, who’s been watching her movements from afar using the same technology you’d use to track a lost phone. The answer is boring: it’s the number on her leg tag. “It’s very scientific,” he jokes. “I don’t subscribe to the kākāpō style of avian research.” That’s where every bird gets a name. Arguably, too, a greater proportion of Rayner’s research subjects die in the field.

Kawau tikitiki are the most glam rock of all the shags. When they’re dry, their head feathers swoosh upwards from their brows and crest over their eyes in a pompadour any lead guitarist would envy. Unfortunately, they also have the same hairstyle in the back. The lime-green and turquoise is their nuptial plumage, aka their town clothes, which they put on from June to October. “Their colours are just ridiculous,” says Rayner. “They’re incredible.”

Kawau tikitiki/spotted shags dress up for the breeding season between June and October: their feathers develop black polka-dots and their faces turn various shades of green.

Rayner has been tracking kawau tikitiki on and off for years. In 2019, he built a fake shaggery on Ōtata, one of the Noises Islands, in the hope of establishing another colony. It hasn’t yet caught on, though the birds visit it often. Later the same year, he joined an international study led by Oregon State University looking at 15 of the world’s 36 cormorant species. (Most other countries call these birds cormorants. Here, they’re kawau, or shags.)

“They’re doing this global analysis, and their thing is using cormorants as sort of sensors in the marine environment to look at fish availability and ocean parameters such as temperature,” he says.

That’s why, last spring, Rayner fitted 10 spotted shags with ultra-fancy solar-powered tags that act like avian fitness trackers, transmitting data on exactly where each shag dives and how deep. “We’ve got like 38,000 dives,” he says. “Some birds are diving up to 400 times a day.” It turns out that compared to cormorants around the world, ours might be working the hardest: diving the longest, flying the furthest.

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When it comes to the fish that shags eat—a number of small fish species collectively known as “forage fish”—we don’t measure or track how they’re doing. We don’t know how many there are, or how their numbers may be changing. “I wish there were some data,” says Rayner.

One of the tracked shags wearing its GPS backpack takes off at a Coromandel mussel farm, where fishing is plentiful. The backpacks fall off over time; five months into the study, only one shag is still transmitting.

We can figure out from studying the birds’ feathers that the food spotted shags eat has changed over time. We know from anecdotal reports from fishers that numbers of some forage fish species have plummeted in the Gulf. And we know that, a century ago, the Firth of Thames and Hauraki Gulf were carpeted with mussel reefs, which fostered whole communities of fish. Those no longer exist.

“We’ve destroyed those habitats either by dredging or by silt coming out of the Waihou River,” says Rayner. “And so now the birds are dependent on the mussel farms.”

Turns out there’s only a sliver of liveable ocean remaining to the birds. “They’re locked into this little area of suitable foraging habitat, and they’re kind of trapped there,” says Rayner. “There’s nothing further up the coast, there’s nothing further down the coast, they’re stuck with what they’ve got. So I think they have to work really hard.”

Shags nest on Tarahiki Island in early spring, commuting to other parts of the Gulf and Firth to fish for their young.

And they lose more of their territory when the shallow water in the Firth heats up at the end of summer. Nutrient-rich water spiked with agricultural fertilisers and effluent washes out of the Waihou and Piako rivers into the Firth year-round—but as the water warms, the shallow basin of the Firth turns into the perfect lab for growing phytoplankton and algae. Those species suck oxygen out of the water, which makes it about as hospitable to ocean life as the planet Venus. “You see this trend in summer of oxygen levels on the sea bottom, in that shallow water, getting to near zero,” says Rayner.

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On Christmas Eve, Shag 224796 started transmitting very odd data. She spent five minutes underwater—a dive is usually less than a minute—before surfacing. Then she travelled to a boat ramp, then four kilometres further inland, where she stayed put. Her tracker was still transmitting, but now, it held still.

After Christmas, Rayner followed the signal to the bird and found her dead body. Her Department of Conservation leg band, the one with her name on, had been ripped off.

She was the first of two shags that Rayner would lose to drowning over the course of the study. Another shag spent ten minutes underwater, about 200 metres off the coast of Thames, before drifting up the Waihou River—suggesting that it, too, had been caught by fishing gear then loosed by someone. Sure, it could have got tangled up in something underwater, says Rayner. But if so, how did it get free?

Rayner’s tracking data shows that spotted shags are hanging out in the same general areas that set-net fishers use, and now, he’s looking into exactly where the two overlap. But he’s only able to study legal set-netters, who must register the GPS position of their nets. Illegal set-netting is rife, according to a January report from Newshub, which found that Auckland fisheries officers were removing around six illegal set nets per week.

The Auckland region’s spotted shag population is a fraction of what it once was. A century ago, there were huge colonies on the west coast as well as in the east. Last century, they were shot in great numbers by fishers who saw the birds as their competitors.

Though Rayner’s study group is small, he’s worried that he lost 20 per cent of it over one summer—one breeding pair out of only 250 or so left.

And it’s not only the Auckland-region shags that are in trouble. A spotted shag survey around Bank Peninsula found a precipitous decline, with the number of birds halving over the five years that Christchurch City Council has been monitoring them.

“As with many seabirds,” says Rayner, “there’s clearly a problem there.”

The solutions Rayner points to aren’t particularly complicated: ban, or even just monitor, the catch of forage fish. Get rid of set-netting, which he calls “an archaic and indiscriminate tool for killing not just target species but a whole lot of other life”.

Restore the mussel reefs that previously exist—there’s already a non-profit attempting to do just that—which would require stopping bottom trawling and reducing the amount of sediment washing into the water. The solution to all that mud is the same as the one for farm runoff: planting and fencing waterways throughout the Hauraki Plains. These changes wouldn’t solely benefit kawau but the other species sharing the same sea and sky and trying to stay alive.

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