Environment – A tale of two gulls

Most of us living on the Coast will see gulls every day and probably not think much of it. It seems that these common, large and noisy scavengers are at best tolerated but sometimes disliked. There are two common local species: the smaller, red-billed gull/tarāpunga and the much larger southern black-backed gull/karoro. You can see lots of pictures on the NZBirdsOnline website. Both species regularly nest on Tiritiri Matangi, but, on the island and nationally, their fortunes are quite different.

First impressions of population size can be misleading as we often see singles of karoro and flocks of dozens of tarāpunga. In 1984 it was estimated there were a million karoro in New Zealand, although it is thought that numbers have declined recently. Karoro are one of only two species of native bird not given any protection under the Wildlife Act. They are responsible for bird-strikes at airports and may attack vulnerable farm animals. Karoro are one of the ‘apex predators’ of the bird world and part of their success story is how well they have adapted to living with humans, taking advantage of landfills, wharfs and industrial food processing to scavenge for food.

A national survey of tarāpunga in 2014 to 2016 found just 27,831 pairs, with around 12,676 pairs in the North Island. They are classed as ‘At Risk: Declining’ in the most recent Conservation Status report. They are typically coastal dwellers and also scavenge at dumps and fish processors. Thousands used to nest on the Mokohinau Islands, but they have largely disappeared from there with only a few hundred pairs in recent years. For successful breeding, The tarāpunga’s diet at large colonies relies mainly on krill. The late Ray Walter, who was the Tiritiri Ranger for many years, was a lighthouse keeper on the Mokohinaus and observed the decline in tarāpunga which he attributed to several years of intense commercial fishing in the immediate area. Mainland breeders are vulnerable to introduced predators.

What of these birds on Tiritiri? Tarāpunga nest in colonies on rock stacks and pinnacles off the east coast of the island. For the 10 seasons from 2013-14 onwards, between 81 and 332 pairs nested with an average of 215 pairs. In 2023-24 we had our first season since we began counting with no nesting tarāpunga, followed by 134 and 136 in the next two seasons. Karoro nest around the edge of the Island either singly or in small colonies. For the seven seasons from 2013-14 onwards we recorded between 26 and 54 pairs with an average of 41 pairs. In the six seasons after that we recorded 5 to 25 pairs with an average of 18 pairs. Karoro nesting has declined by around 56 per cent.

So, wherever you are on the Coast, pay a little attention to these beautifully plumaged gulls. Despite their apparent abundance, there’s a lot going on in their lives and their future is not necessarily secure.