White-fronted Tern. Photo: Abe Borker
These sleek white-fronted tern are a fairly common sight along our coasts. Fishers call them ‘kahawai birds’ because flocks will be very active over kahawai schools, feeding on the small fish that the kahawai also pursue. They feed by diving, not deep-plunge diving like gannets, more a dipping dive to snatch prey just below the surface. They can carry these small fish, draped in their bills, back to their nesting grounds, to either entice a mate during courtship or feed a chick. They make their nests on rocky headlands, cliffs and stacks, on shell and sand islands in estuaries, and on sand dunes and river beds. Some determined birds will also nest on breakwaters and even on abandoned coastal structures, like old wharves and bridges. They raise one, sometimes two chicks, and although these little fluff balls are beautifully camouflaged, they can fall prey to dogs, cats, rats and hedgehogs.
When people, or predators, approach nesting areas, the adult birds will bravely dive at the intruder to try to scare them away. Black-backed gulls will also prey on eggs and chicks, as do harriers. Some tern colonies are sited strategically close to red-billed gull colonies, another bird that will aggressively chase away intruders.
The Maori name for the white-fronted tern is ‘tara’, and the number of small rocky islands called Motutara indicate their liking for breeding there, or using them for roosts close to favourite fishing grounds.
Something to look out for as you head out for a day’s fishing is to spot a group of terns, white dots hovering, sometimes diving. Then look at the sea surface and you might pick out little penguins, also feeding on the same fish as the terns. But keep your eye on those terns, and you could see another type of action – dramatic aerial pursuits made by skua trying to get the terns to drop their hard-won fish. You’ll see the terns ducking and weaving, using their long tails to help them manoeuvre. But skua are persistent and also remarkably manoeuvrable. If it succeeds in getting the tern to drop its catch, it will swoop down and grab the fish, often before it hits the water. Klepto-parasitism (one animal robbing another of its prey) is seen among a number of seabirds in northern New Zealand, including the various skua species, gulls and also amongst shearwaters.
While white-fronted terns are most commonly seen close to the coast, you can also see them out in open water. Their high pitched ‘siet’ call will alert you to their presence; look up and you will see two or three of these birds flying through. If want to get close views of these birds, now is a good time when they are not breeding. Estuaries such as Orewa, Wenderholm, Pakiri, Mahurangi and Waipu are good places. They can be seen in groups roosting on the sand, or bathing in the water nearby. At Motuihe Island, in the inner Hauraki Gulf, the line along the railings of the wharf often feature a tern guard of honour for visitors. That is until they all fly off until the disturbance has passed.
In northern New Zealand, there appears to have been a decline in the numbers of white-fronted terns, with concern expressed in conservation circles that this once very common species may one day disappear from the north. As with several seabirds that feed in association with schooling fish, such as kahawai and trevally, this is an area where research into their foraging ecology and population biology, complemented by studies into the dynamics of schooling fish, is urgently required. Something we at the Seabird Trust are working on with government agencies and universities.