Northern giant petrel  (Macronectes halli)

The northern giant petrel is classified as Least Concern (LC) on the IUCN Red List (1).

The northern giant petrel (Macronectes halli) is a large petrel the size of a small albatross with a large wingspan and an enormous bill. Like all other petrel species it has a single tubular nostril on the top of the bill. Adults have a largely grey-brown body, with an off-whitish head, neck and breast (2) (3). The eyes are pale grey and the bill is pinkish-yellow, with a red-brown tip (2) (3). Although the sexes are similar in overall appearance, the male is conspicuously larger and heavier-billed than the female (2). The juveniles are darker, almost sooty black, and become paler with age (2) (3).

This northern giant petrel is very similar in appearance to the southern giant petrel (Macronectes giganteus), and it took until 1966 before it was recognised that they were actually two species (4). The darker tip of the bill is the main distinctive feature to discriminate this species from the southern giant petrel (3).

The northern giant petrel has a circumpolar distribution in open oceans, mostly between 40 degrees and 64 degrees south (2). Because both giant petrel species are difficult to distinguish at sea, the exact  distribution of this species is difficult to determine. Some individuals do occur in subtropical waters during the winter and early spring, up to 28 degrees south, but these are most likely juveniles (2) (3).

The movements of adult southern giant petrels over winter are not fully understood, but some have been observed to remain near the breeding colonies throughout the year, whilst others travel great distances across the ocean (2) (3). Although the name suggests that this species occurs more northerly than its southerly sibling species, this is not completely true. The northern limits of both species are very similar, but the northern giant petrel does not disperse as far south as its sibling species (2) (3). The southern giant petrel is seen virtually always north of the Antarctic Polar front and is thus absent around the coast of Antarctica (2) (3).

Breeding populations are currently found at South Georgia, Prince Edward Island (South Africa), Crozet and Kerguelen Islands (French Southern Territories), Macquarie Island (Australia), and Auckland, Campbell, Antipodes and Chatham Islands (New Zealand) (5).

The northern giant petrel frequents both oceanic and inshore waters, near breeding islands and outside of its breeding range. Breeding sites are typically located on low areas close to the sea, on coastlines with tussock grass and broken terrain that provide shelter for nests (3) (6).

The northern giant petrel breeding season generally begins towards the end of the Austral winter, with pairs establishing a nest site in August and laying a single egg between August and October (7) (8). The small, loose breeding colonies generally comprise less than 50 pairs, with the untidy nests dispersed widely amongst tussock grass and rocky out-crops (3). The eggs are incubated for around 60 days, and the chicks fledge around 108 days after hatching (2) (3). Reproductive maturity is reached at around six years of age, but most individuals first breed three to five years later (3) (7) (8).

Northern giant petrels are the scavengers in the Southern Ocean. The large beak is particularly well designed for tearing flesh. They feed opportunistically on a wide variety of prey including seal, whale, and penguin carrion, krill, octopus, squid, fish and other seabirds (3) (6) (9). Females forage mostly over the ocean, but males scavenge more on land for seal and penguin carcasses (3) (9) (10). At sea, both male and females are aggressive and often gregarious when feeding, taking most prey by seizing it at the surface, or briefly diving into the water (3) (6). In addition, this species commonly scavenges for fish and offal discarded from ships, often feeding near trawlers and longliners (5) (6) (9).

At some localities where both northern and southern giant petrels breed, some interbreeding between the sibling species occurs. However, the occurrence of hybrid northern and southern giant petrel chicks is rather low because of the difference in the timing of breeding of both species. Northern giant petrels breed six weeks earlier on locations where also southern giant petrels breed (7).

By far the most serious threat to the northern giant petrel is incidental mortality in long-line fisheries (3) (6) (9). Both giant petrel species frequently follow longline fishing vessels, and in the process of competing for baits often become hooked and drown, or ingest discarded hooks leading to serious injury (6). In addition, human disturbance and predation by feral rats and cats may have had some negative impact on giant petrel populations. It is not known to which extent threats such as oil spills, entanglement in marine debris, ingestion of plastics, the accumulation of chemical contaminants present further risks (6) (10).

Since the 1980s the global breeding population of northern giant petrels has increased to an estimated number of 11,200 breeding pairs in the late 1999s (5). The reason for this increase is not fully clear, because most censuses were irregular and rather infrequent. However, it is likely that the implementation of measures to reduce bycatch in fishery activities, as well as greater availability of food, such as carrion from expanding fur seal populations, and increased food waste from ships may have caused a population increase (5) (9)

According to the IUCN Red list this species is not threatened, but frequent fatal interactions of both giant petrel species with fisheries deserve special attention. The northern giant petrel is listed on Appendix II of the Convention on Migratory Species (CMS) and Annex 1 of the Agreement on the Conservation of Albatrosses and Petrels (ACAP) (9) (11) (12). Both these listings serve to promote international collaboration in the conservation and management of this species (11) (12). The current conservation measures being prioritised are to promote the use of bycatch reduction measures by all fisheries within this species’ range, to minimise disturbance at breeding sites, and to continue monitoring the population and conduct further research into its year round movements (5) (9) (10).

View information on this species at the UNEP World Conservation Monitoring Centre.

Further information on the conservation of petrels: 

• Agreement on the Conservation of Albatrosses and Petrels (ACAP):
  www.acap.aq

More information on the northern giant petrel and other bird species:

• BirdLife International:
  http://www.birdlife.org