Chatham Island shags nesting. Photo: Supplied / Chatham Island Landscape Restoration Trust.
Five Chatham Island shags fitted with tiny bluetooth backpacks have provided some good-news data to bird conservationists.
Run by the Chatham Island Landscape Restoration Trust with funding from the Department of Conservation, the tracking programme saw birds from a colony near Manukau Point fitted with trackers and monitored for more than three weeks.
Ornithologist Mike Bell said it was a good test for a new type of tracker, made by Druid, taped on using Tesa tape.
Each bird weighed about three kilograms, standing about 50 centimetres tall - "not small," Bell said.
He and colleague Hamish Chisholm caught them using a bit of stealth and a modified shepherd's crook, and fitted the tags.
Then, Bell visited the colony every two days to collect data from the new tags, which used bluetooth to transmit information to a phone, rather than sending it via a satellite.
Mike Bell and Hamish Chisholm tag shag birds on Chatham Island. Photo: Supplied / Chatham Island Landscape Restoration Trust.
This saved money at both ends, Bell explained the transmitters themselves were cheaper - in the ballpark of $400, compared to $2000 - and they didn't result in satellite charges.
"On dusk every second day, I'd go to the colony, wait for the shags to come home and then connect with my phone to each device as the bird came in, and download the data."
While the sample size was "pretty small", he said, "the results were amazing".
It showed the birds were foraging at sea for short periods and each bird had its own distinct foraging ground, travelling 7-15km from the colony to the same spot each day.
They didn't stay out very long, compared to other shag populations, and individual birds would share the food foraging duties with their mates, which indicated food was in good supply, Bell said.
"They feed on the bottom, so some of these guys, looking at where they're going, are probably diving about 90 metres," Bell said - and other shag species could dive as deep as 200 metres.
They would stay out for 4-5 hours, before returning home.
"They're pretty epic at what they do," Bell said.
One behaviour had surprised him.
"Three birds overnighted at another colony. For birds pre-breeding to be disappearing and hanging out on another colony is really interesting behaviour," he said.
"A couple of nights when birds didn't come back, I was, like, 'Oh my god', a bit worried, but then I'd go back the next day and it was back, and of course you get the tracking data."
What were these birds doing?
"Could be the males having a little bit on the side," Bell said.
"We know that lots of seabirds, even though they pair for life, are not completely faithful and a bit of fence-jumping goes on."
Bell said the next step was to hopefully gain a bit more funding to continue the research and track more shags from different colonies.
The trust thanked Chatham residents Maui Solomon and Susan Thorpe for their support, and for allowing them access to the colony.
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