Community collaboration protects threatened gulls at the Charwell River
Classified by Te Papa Atawhai/Department of Conservation (DOC) as at risk and declining, the black-billed gull/tarāpuka is under threat of extinction. So when we were given the heads up about a colony in a North Canterbury river, we established a predator control programme in the hopes of improving their chances of breeding success.
Trapping supports breeding success
Although many of us associate gulls with the coastal environment, tarāpuka typically establish breeding colonies on braided rivers, inland lakes and, occasionally, farmland. Their preference for breeding at inland sites makes them especially vulnerable to flooding, human disturbance and mammalian predators, such as rats, weasels, ferrets, stoats and hedgehogs. They also face predation from the sky, with harrier hawks, and the heftier Southern black-backed gull/karoro, proving a major threat to ground-nesting birds such as tarāpuka.
Between September 2022 and February 2023 – the braided river bird nesting season – our Senior Biodiversity Officer Heath Melville worked with Toitū Te Whenua Land Information New Zealand (LINZ) and DOC on a trapping programme designed to support the breeding success of tarāpuka at the Charwell River site. The Kaikoura Community Shed also lent a hand, building 30 predator traps to support the work.
“We assumed the full range of mammalian predators would be there – feral cats, ferrets, stoats, weasels, rats and hedgehogs,” Heath said.
“Sure enough, the 46 traps we laid caught some of everything. Even when we dialed back trap checks to monthly after the tarāpuka had left the site, we were still catching the full suite of mammalian predators, even when the bait was three-to-four-weeks old.”