Bay of Plenty oilspill – Potential for impacts on seabird populations

Bay of Plenty oilspill – Potential for impacts on seabird populations

New Zealand marine areas are home to a wide variety of wildlife, with many unique and threatened species inhabiting our waters. New Zealand’s title as World Seabird Capital is unchallenged, with 1/3 of the worlds’ 346 species present in the New Zealand Exclusive Economic Zone, including ½ of the 22 albatross species of the world. A high proportion (40%) of the worlds albatrosses and their smaller cousins, the petrels and shearwaters breed in New Zealand. Nineteen of these species breed only in New Zealand, and 18 of these are threatened with extinction. The Bay of Plenty is a rich environment for feeding for these species, and many of its small islands are refuges for vulnerable species.

The endemic Black Petrel Procellaria parkinsoni is one example, listed as Vulnerable by the IUCN. The breeding population is estimated at around 1750 pairs of nesting birds. Nesting only on Great and Little Barrier Island, the Black Petrel is active around the Bay of Plenty where the Rena oil spill has occurred. Black Petrels begin to return to their breeding colonies in early October, and feed extensively at this time of year around eastern New Zealand in preparation for egg-laying in November.

Black Petrel (Procellaria parkinsoni)
Black Petrel (Procellaria parkinsoni). Reproduced courtesy of Wikimedia under a CC-BY-3.0 licence

The Black Petrel species is subject to threats from predation at the breeding sites by cats and other introduced predators, and are killed in longline fisheries in New Zealand northern waters.  Any mortality of Black Petrels in the oil spill will be to adding to other deleterious influences on the population and may have very serious impacts on the population as a whole.

Research into the ability of seabird populations to cope with additional mortality has been conducted by the Ministry of Fisheries and has shown that only a small number of additional deaths can be sustained for adult seabirds of many species in the Bay of Plenty area. Additional deaths above the expected ‘natural’ deaths have potential to result in population declines for rare species such as the endemic Black Petrel. Cumulatively, deaths from fishing, and oiling add to unusual climatic incidents like this year’s very strong La Nina weather conditions, and can put a great deal of stress on fragile populations. Reduced numbers of adults of long lived species such as shearwaters and petrels has potential to have a very great effect on the sustainability of their populations, as adults killed in events such as oil spills leave young to die in the nest, and partners to the dead birds may take many years to re-mate.

Another threatened seabird species breeding in the Bay of Plenty is the Pycroft’s petrel, with its major breeding centre on the Mercury Islands. Some populations of seabirds, significant at a national level, breed in the Bay of Plenty – Coromandel area and depend on resources in the Bay of Plenty for food. These include large populations of Flesh-footed Shearwaters (Alderman Islands, Karewa Island, Ohinau Island), Common Diving Petrels (Mercury Islands) and Australasian Gannets (Whale Island).

New Zealand Birds: Gannets, Cape Kidnappers, 1960 s - 1980 s, Hawke's Bay. Brake, Brian. Gift of Mr Raymond Wai-Man Lau, 2001. Te Papa
New Zealand Birds: Gannets, Cape Kidnappers, 1960 s – 1980 s, Hawke’s Bay. Brake, Brian. Gift of Mr Raymond Wai-Man Lau, 2001. Te Papa

Reef structures can operate like oases in the otherwise sparse feeding environment of the offshore marine systems of New Zealand. Their physical structure catches the current and planktonic larvae settle, out so they support many marine life-forms. Around the reef predatory fish, and other top predators such as whales and seabirds congregate to snatch fish.

Astrolabe Reef is a really well known diving and fishing spot, removed from the effects of coastal sedimentation so has very clear water. This results in a rich algal and invertebrates (sponges, tubeworms, and the like) assemblage and with this comes a very diverse fish community. If the oil and dispersant impact on the algae and invertebrates then the reef community will be significantly degraded. Recreational species like rock lobster, snapper and kingfish are all targeted and obvious, but there also the smaller ‘hidden’ ones like pink cusks and triplefins. These, like the algae kina, paua and sponges, are permanent inhabitants of a reef and incapable of moving on when the habitat is adversely effected by something as toxic as an oil spill and dispersant. The Bay of Plenty is the southern limit for some fish species and the off-shore islands and reefs are the best place to observe them.

Common triplefin, Forsterygion lapillum Hardy, 1989, collected 13 Aug 1991, 750 m South of Tuingara Point, Pourerere, Hawke's Bay, New Zealand. Te Papa
Common triplefin, Forsterygion lapillum Hardy, 1989, collected 13 Aug 1991, 750 m South of Tuingara Point, Pourerere, Hawke’s Bay, New Zealand. Te Papa

Oil impacts marine life in a variety of ways, physically coating surfaces and through toxic effects which can affect vital elements such as organs functions and respiration. Recovery of oiled wildlife can be a tenuous process, with many oiled birds suffering damage to their feathers, but also their internal organs as they injest oil when they preen their feathers to clean them. Recovery of oiled birds is possible, but very resource intensive. A large facility to cope with oiled wildlife at Phillip Island, near Melbourne has capacity to cope with 1500 penguins at a time, and is Australia’s answer to dealing with this problem. New Zealand has no centre of comparable capacity at this time.


  1. Hi Colin

    Grey ternlets have their centre of distribution on the Kermadec Islands, with small numbers visiting a few sites of the north-east New Zealand coast in late summer: Mokohinau Islands, Sugarloaf Rock (Poor Knights Islands), and the Volkner Rocks. Only the latter is in the Bay of Plenty. It is not known if grey ternlets occur on the Volkner Rocks every year, and when they do it is in low numbers. It is unlikely that any would be present at this time of year.

    Colin Miskelly
    Curator Terrestrial Vertebrates
    Te Papa

  2. And how about the grey ternlet colony on Volkner Rocks. When do they breed and are the feeding adults, then fledged juveniles at risk?

Leave a Reply

Your email address will not be published. Required fields are marked *