Since we drove over the Hakatere River and saw the colony just over the side of the bridge in Ashburton, I’ve been thinking of those black billed gulls and their plight. They are New Zealand’s only endemic gull and are known as the most threatened gull in the world. In 2009 there were about 140,000 of them and today it is estimated that there are only 15,000 left. They are in rapid decline.
They breed on the braided rivers of the South Island along with Pied Stilts, Wrybills and Pied Oystercatchers. Banded Dotterels also use the rivers. Gulls breed in large colonies to protect the young from aerial predators. The large amount of flying birds confuse them.
Braided Rivers are found in only a few places in the world. New Zealand, the Himalayas and parts of North America. The environment around the rivers in New Zealand are almost entirely altered since people arrived with introduced plants, predators, and pollution.
Riverbanks are now thick with broom, gorse, and dense mats of agressive grasses. These consolidate the gravel so that the river is not free to meander, even in big floods, causing the rivers to silt up and the introduced plants to grow thick on areas of gravel previously used as nesting places.
Humans use the rivers for pleasure tearing around on four wheel motorbikes and vehicles, and even having fun running through the breeding colonies. The eggs and chicks are very hard to spot amongst the stones and gravel. Birds are used as target practice and jet boats tear along the channels and lagoons frightening birds and swamping eggs and chicks. The thoughts are that they are just seagulls. Red Billed Gulls are also in decline and a worry. Something needs to be done and soon. Maybe the river areas should be a no go area during the breeding season say September to February or March.
Predators are the other major concern. Cats, rats, weasels, and stoats. The rivers can’t be fenced off and an awful amount of traps would be required and the maintenance of them expensive.
So all in all, there is no simple solution, but doing nothing is not an option.