Kia Pākiki Canterbury – black-backed gulls
Wendy Fox studies black-backed gulls/karoro (Larus dominicanus) at Lincoln University, where she’s interested in finding out more about their movements and breeding success. Black-backed gulls are the largest species of gull in Aotearoa New Zealand. Wendy describes them as “the big black and white scary ones with the big yellow beaks and the big black backs. And they definitely do like stealing people’s chippies because, you know, why wouldn’t you? Chippies are delicious.”
Kia Pākiki Canterbury – black-backed gulls
In this Kia Pākiki Canterbury podcast, Associate Professor Adrian Paterson from Lincoln University interviews Wendy Fox, also from Lincoln University.
Select here to view video transcript and copyright information.
Learning about karoro
Karoro are one of only two New Zealand bird species not protected under the Wildlife Act 1953 – the other is the spur-winged plover (Vanellus spinosus). Wendy explains that this is because karoro have done very well thanks to humans. “Their population is higher than it would naturally have been,” she says, “which is good for them population-wise but bad for other species.” As a result, karoro are controlled and managed in some parts of the country to reduce their predatory behaviour towards farm animals and some threatened species of shorebirds.
Southern black-backed gull
Karoro, the southern black-backed gull (Larus dominicanus), makes its home in braided riverbeds, estuaries and even roofs.
Wendy’s interested in the birds’ colony-forming behaviour. “You find them everywhere,” she says. “They’re very versatile and adaptive animals. They’re amazing.” They like to nest in braided riverbeds and can also be found in estuaries, near cliffs and even on residential or commercial roofs.
Black-backed gulls are long-living birds. The average lifespan is about 14 years, says Wendy, and the oldest recorded karoro is 28 or 29 years old. The birds start breeding at 4 years of age, though Wendy says some can start breeding at only 3, and most breed for around 10 years. “They definitely have the potential to breed in good numbers,” Wendy says.
Drop traps and GPS trackers
Even though karoro population numbers are high and the birds are seen everywhere, we don’t know that much about them, says Wendy. Very few have been banded to keep track of them. “There was a lot of banding done between about the 60s up until kind of the 80s, early 90s … but very little has been done since then. So we don’t really know who’s flying from where, whether they have big territories or small territories”, says Wendy. “So being able to track them and see where they fly has been really interesting.”
That tracking is enabled by tiny GPS trackers fitted to birds. Wendy catches the karoro in a drop trap, which she describes as, “A bit like Wile E. Coyote. So basically a metal cage with bird netting over it propped up by a stick over their nest … and then catch them and wrap them up like a little burrito in a towel.” The birds are assessed for general health and weighed to assess their suitability for the GPS tracker, as the tracker has to be no more than 3% of the bird’s body weight. The trackers run off the cellular network and are able to send more frequent updates when the birds are in flight. Wendy notes, “You get to see these really cool flight patterns throughout the landscape, which is awesome when you put it on a map.”
And where are the birds going? “Everywhere, because they’re super cool,” she says. During the breeding season, the birds tend to stick within about 10 kilometres of their breeding colony, but the rest of the time “they fly all over the place”.
Highly intelligent gulls
“I knew they were smart, but I didn’t realise quite how smart they were,” says Wendy. She’s had insight into the birds’ cleverness while collecting data out in the riverbeds.
Karoro, southern black-backed gull
Karoro, the southern black-backed gull (Larus dominicanus), lives to an average age of about 14 years. They frequent beaches, landfills, ports and human habitations. The birds can be a nuisance and are controlled in some areas.
“Within a few weeks, they will recognise me and they’ll recognise the car,” she says. “Birds will come over, put out the call like, ‘Oh my goodness, she’s back.’ And then the colony becomes chaos, and all the adults are lifting off and telling their children to hide, so I can’t count them. It’s incredible. I don’t even have time to get out of the car, and they’re like, ‘It’s her. It’s her car. She’s back again. The crazy bird lady. Hide your children!’”
Another example of karoro’s uncanny intellect came when Wendy was first starting out catching the gulls for fitting GPS trackers. “I thought that I was going to be able to catch all the birds from one colony,” she says. But after catching one bird, the rest of the karoro simply would not come near the trap. “These birds had never been caught before,” Wendy explains. “They’d literally seen the trap once, and it was like, ‘Nah, not having a bar of that.’ So we had to change our tactics.”
It’s not just karoro that fascinate Wendy. She’s also interested in the migratory habits of banded dotterel/pohowera (Anarhynchus bicinctus). Some stay fairly close to home during winter, whereas others will fly as far afield as Australia. “Which just makes me think,” muses Wendy, “why do the same birds in the same area do very different things? So I think a universal translator would be great.”
Related content
The Hub has an extensive range of resources featuring birds:
For all of our articles and activities, browse through our Birds topic.
For more on populations, see Population biology.
We have repurposed the popular Building Science Concepts Book 3 Birds: Structure, Function, and Adaptation with an article and interactive linking this great resource with Hub content.
Find out how scientists track godwits on their amazing 12,000 km flights.
Useful links
Other resources you may find useful:
Department of Conservation – Five-minute bird counts
Department of Conservation – Birds A–Z
Te Papa – Birds of Aotearoa New Zealand
Visit the New Zealand Birds Online website for additional information about karoro.
Acknowledgement
This interview was excerpted from an episode of Kia Pākiki Canterbury, a monthly podcast about science, technology and humanities presented by the Canterbury branch of the Royal Society Te Apārangi.
Kia Pākiki logo
Kia Pākiki Canterbury is a monthly podcast about science, technology and the humanities presented by the Canterbury branch of the Royal Society Te Apārangi.
