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Giant petrel
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Giant petrel
Temporal range: Pliocene[1] – recent
Southern giant petrel juvenile
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Procellariiformes
Family: Procellariidae
Genus: Macronectes
Richmond, 1905
Type species
Procellaria gigantea
Gmelin, 1789
Species

Macronectes giganteus
Southern giant petrel
Macronectes halli
Northern giant petrel
Macronectes tinae
Tina's giant petrel

Giant petrels form a genus, Macronectes, from the family Procellariidae, which consists of two living and one extinct species. They are the largest birds in this family. Both extant species in the genus are native to the Southern Hemisphere. Giant petrels are extremely aggressive predators and scavengers, inspiring another common name, the stinker.[2] Seamen and whalers also referred to the giant petrel as the molly-hawk, gong, glutton bird and nelly.[3] They are the only member of their family that is capable of walking on land.[4]

Taxonomy

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The genus Macronectes was introduced in 1905 by the American ornithologist Charles Wallace Richmond to accommodate what is now the southern giant petrel. It replaced the previous genus Ossifraga which was found to have been earlier applied to a different group of birds.[5][6] The name Macronectes combines the Ancient Greek makros meaning "great" and nēktēs meaning "swimmer".[7]

The present-day giant petrels are two large seabirds from the genus Macronectes. Long considered to be conspecific (they were not established as separate species until 1966),[8] the two species, the southern giant petrel, M. giganteus, and northern giant petrel, M. halli, are considered with the two species of fulmars, Fulmarus, to form a distinct subgroup within the Procellariidae, and including the Antarctic petrel, Cape petrel, and snow petrel, they form a separate group from the rest of the family.[9]

A fossil giant petrel, Macronectes tinae is known from the Pliocene epoch of New Zealand.[1]

Genus Macronectes – Richmond, 1905 – three species
Common name Scientific name and subspecies Range Size and ecology IUCN status and estimated population
Southern giant petrel, Antarctic giant petrel, giant fulmar, stinker, and stinkpot

 Macronectes giganteus
(Gmelin, 1789) 		Antarctica to the subtropics of Chile, Africa, and Australia
Map of range 		Size:

Habitat:

Diet: 		 LC 


Northern giant petrel or Hall's giant petrel

 Macronectes halli
Mathews, 1912 		Southern Ocean north of the Antarctic Convergence Zone, and north through Chile, Argentina, South Africa, and half of Australia.
Map of range 		Size:

Habitat:

Diet: 		 LC 


Tina's giant petrel, Taranaki giant petrel

 Macronectes tinae
(Tennyson & Salvador, 2023) 		extinct (New Zealand, Pliocene) Size:

Habitat:

Diet: 		 EX 



Distribution

[edit]

The living species are restricted to the Southern Hemisphere, and though their distributions overlap significantly, with both species breeding on the Prince Edward Islands, Crozet Islands, Kerguelen Islands, Macquarie Island, and South Georgia, many southern giant petrels nest farther south, with colonies as far south as Antarctica. In July 2019, an individual, either of M. giganteus or M. halli, was found as a vagrant in County Durham and Northumberland in the United Kingdom, marking the first record of the genus in Europe.[10]

Description

[edit]

The southern giant petrel is slightly larger than the northern giant petrel, at 3 to 8 kg (6.6–17.6 lb), 180 to 210 cm (71–83 in) across the wings, and 86 to 100 cm (34–39 in) of body length.[2][11] The northern giant petrel is 3 to 5 kg (6.6–11.0 lb), 150 to 210 cm (59–83 in) across the wings and 80 to 95 cm (31–37 in) of body length.[12][13] They superficially resemble the albatross, and are the only procellarids that can equal them in size. They can be separated from the albatrosses by their bill; the two tube nostrils are joined on the top of the bill, unlike on albatross, where they are separated and on the side of the bill. Giant petrels are also the only members of the family Procellariidae to have strong legs to walk on land.[2][4] They are also much darker and more mottled brown (except for the white morph southern, which are whiter than any albatross) and have a more hunch-backed look. The bills of Procellariiformes are also unique in that they are split into between seven and nine horny plates. The petrels have a hooked bill called the maxillary unguis which can hold slippery prey. They produce a stomach oil made up of wax esters and triglycerides which is stored in the proventriculus. This can be sprayed out of their mouths as a defense against predators and as a protein-rich food source for chicks and for the adults during their long flights.[14] Petrels have a salt gland situated above the nasal passage that helps to desalinate their bodies by excreting a high saline solution from their noses.[15]

The two species are difficult to tell from each other, possessing similar long, pale, orange bills and uniform, mottled grey plumage (except for around 15% of southern petrels, which are almost completely white). The billtip of M. halli is reddish-pink and that of M. giganteus is pale green, appearing slightly darker and lighter than the rest of the bill, respectively. The underside of older M. halli birds is paler and more uniform than M. giganteus, the latter showing a contrast between paler head and neck and darker belly.[16] Additionally, adults of M. halli typically appear pale-eyed, while adults of M. giganteus of the normal morph typically appear dark-eyed (occasionally flecked paler). Classic examples of northern giant are identifiable at some range. Young birds of both species are all dark and very hard to distinguish unless bill tip colour can be seen. Some relatively young northern giant petrels can appear to be paler on the head, suggesting southern giant, thus this species is harder to confirm.[citation needed]

The extinct Macronectes tinae is characterized by having smaller bodies than their living relatives.[1]

Etymology

[edit]

Macronectes comes from the Greek words makros meaning "long" and nēktēs meaning "swimmer". Also, petrel is derived from St. Peter and the story of his walking on water, as they appear to run on the water when they take off.[17]

Giant petrel feeding on a seal carcass in South Georgia

Behaviour

[edit]

Feeding

[edit]

Petrels are highly opportunistic feeders. Unique among procellarids, they will feed both on land and at sea; the majority of their food is found near coastlines. On land, they feed on carrion,[2][16] and regularly scavenge the breeding colonies of penguins and seals. They will display their dominance over carcasses with a "sealmaster posture":[18] the head and the wings are held outstretched, the head pointing at the opponent and the wingtips pointing slightly back; the tail is raised to a vertical position. Giant petrels are extremely aggressive and will kill other seabirds (usually penguin chicks, sick or injured adult penguins and the chicks of other seabirds), even those as large as an albatross, which they kill either by battering them to death or drowning.[19] At sea, they feed on krill, squid, and fish. They often follow fishing boats and other ships, in the hope of picking up offal and other waste.[16]

Giant petrel with chick in Antarctica

Reproduction

[edit]

The southern giant petrel is more likely to form loose colonies than the northern, both species laying a single egg in a rough nest built about 50 cm (20 in) off the ground. The egg is incubated for about 60 days; once hatched the chick is brooded for three weeks. Chicks fledge after about four months, but do not achieve sexual maturity for six or seven years after fledging.[2]

Conservation

[edit]

While both species were listed as near threatened in the 2008 IUCN Red List,[20][21] subsequent evidence suggested they were less threatened than previously believed, and the populations of both actually appeared to have increased, at least locally. Consequently, they were listed as least concern on the 2009 Red List[16][22] and afterwards (as of IUCN's last assessment in 2018, they continue to be listed as least concern).[20][21]

The southern giant petrel is listed as endangered on the Australian Environment Protection and Biodiversity Conservation Act 1999, while the northern giant petrel is listed on the same act as vulnerable.[12][23][24] Their conservation status also varies from state to state within Australia.[12][23]

Conservation Status of Macronectes species in Australian States
State Macronectes halli Macronectes giganteus
NSW Vulnerable[12][25] Endangered[23][26]
QLD Vulnerable[12][27] Endangered[23][27]
SA N/A Vulnerable[23][28]
TAS Rare[12][29] Vulnerable[23][29]
VIC Endangered[12][30] Endangered[23][30]
[edit]
  • Giant petrel which has just killed a king penguin chick
    Giant petrel which has just killed a king penguin chick
  • Giant petrel flying above South Georgia Island
    Giant petrel flying above South Georgia Island

References

[edit]

Sources

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Giant petrel

View on Grokipedia
from Grokipedia
The giant petrels (genus Macronectes) comprise two of large seabirds in the family , the (M. giganteus) and the (M. halli), which are among the largest members of the order . These birds measure 80–99 cm in length, with wingspans of 150–220 cm and body masses of 2–4 kg, exhibiting pronounced where males are up to 40% heavier than females; the southern shows polymorphism with dark (predominantly grey-brown) and rare white morphs, while the northern is mostly dark with some pale-headed individuals. Both species are circumpolar breeders in the , nesting in loose to dense colonies on sub-Antarctic islands such as , the , and , as well as some Antarctic coastal sites for the southern species, with foraging ranges spanning over 130 million km² in the . They are highly opportunistic and aggressive feeders, primarily scavenging carrion from seals, , and whales, but also preying on , squid, fish, and seabirds, often kleptoparasitizing other birds or following fishing vessels for ; unlike most procellariids, they walk adeptly on land to access carcasses. Breeding occurs annually, with the southern species from to and the northern species starting approximately six weeks earlier; pairs return to the same sites to lay a single large in a nest, incubating it for about 55 days and fledging chicks after 100–140 days; adults first breed at 7–10 years and exhibit high survival rates of around 90%. Both species are classified as Least Concern by the IUCN (), with global populations estimated at 95,600–108,000 mature individuals for the southern (2007) and 23,600 for the northern (2001), showing overall increasing trends due to access to discards, though threats include incidental in longline fisheries and human disturbance at colonies.

Taxonomy and Etymology

Taxonomy

The Macronectes is classified within the family of the order , and it was established by the American ornithologist Charles Wallace Richmond in 1905 to accommodate large seabirds previously grouped under other taxa. Two extant are recognized in the genus: the (Macronectes giganteus), first described by Johann Friedrich Gmelin in 1789 based on specimens from southern oceanic regions, and the (Macronectes halli), originally described as the subspecies Macronectes giganteus halli by Gregory M. Mathews in 1912, and elevated to full species status in 1966 by W. R. P. Bourne and J. Warham following observations of distinct forms during expeditions. The species distinction arose from initial morphological variations, including differences in overall size, eye coloration (pale in M. halli versus dark in M. giganteus), bill structure, and largely non-overlapping breeding ranges (M. halli primarily subantarctic islands north of the , M. giganteus more southern), which were later corroborated by genetic analyses. An extinct species, Macronectes tinae, was described in 2023 from late (Piacenzian, approximately 3.3–3.0 million years ago) fossils recovered from the Tangahoe Formation in South Taranaki, , consisting of a near-complete and a fragmentary . This represents the first pre-Quaternary record of the and suggests that Macronectes had already diverged from closely related procellariids, such as the fulmar Fulmarus, earlier than previously estimated by molecular clocks (potentially over 15 million years ago), highlighting a prolonged evolutionary history of scavenging seabirds in the warming during the . Phylogenetically, Macronectes is closely allied with other procellariids, particularly the Fulmarus clade, within the broader radiation, as confirmed by complete mitogenome sequencing that places the genus firmly in . Evidence from mitochondrial gene sequences reveals a low but diagnostic divergence of 0.42% (uncorrected) between M. halli and M. giganteus, with the northern species forming a monophyletic nested within the paraphyletic southern species, indicating a recent event around 0.2 million years ago during the Pleistocene. Nuclear microsatellite loci further support this phylogeographic separation, showing distinct frequencies and minimal hybridization, consistent with isolation by breeding range and historical glacial fragmentation in the ; however, subsequent studies have documented rare hybridization and back-crossing in sympatric breeding areas, such as .

Etymology

The genus name Macronectes is derived from the words makros, meaning "long" or "large", and nēktēs, meaning "swimmer" or "to swim", reflecting the birds' strong swimming capabilities on the ocean surface. The common name "" traces its origins to the Petrus (Peter), a form linked to the biblical walking on water, inspired by the seabirds' characteristic pattering or "running" across the water during takeoff. The descriptor "giant" in "giant " underscores their substantial size relative to other petrel species, often exceeding 90 cm in length and 2 m in . Additional vernacular names include "stinker" or "stinkpot", arising from the pungent, oily substance these birds regurgitate as a defensive mechanism, producing a strong . They are also known as "giant fulmar", a term evoking their superficial resemblance to (from fúlmari, meaning "foul gull") combined with albatross-like proportions and scavenging habits. For the two recognized species, the southern giant petrel (Macronectes giganteus) receives its specific epithet from the Latin giganteus, denoting "giant-like" in reference to its imposing stature. The northern giant petrel (M. halli) is named in honor of Robert Hall (1867–1949), the Australian ornithologist and collector who documented specimens from breeding sites such as the Kerguelen Islands.

Description

Morphology

Giant petrels (genus Macronectes) are the largest members of the family, exhibiting a robust, heavy-bodied structure that superficially resembles albatrosses but is distinguished by paired tubular nostrils fused at the base atop , a diagnostic trait of procellariids. These birds possess strong, sturdy legs well-adapted for terrestrial walking and scavenging on shorelines, unlike the weaker legs of most other ; a short, rounded tail; and long, narrow wings optimized for efficient long-distance soaring over open oceans. Their overall build supports an opportunistic lifestyle involving both aerial and ground-based activities, with powerful flight muscles enabling sustained without frequent flapping. The (M. giganteus) is the larger of the two , measuring 85–100 cm in length, with a of 150–210 cm and body of 3.8–5.0 kg; males exhibit pronounced , being up to 15% larger in linear dimensions and 40% heavier than females. In contrast, the (M. halli) is slightly smaller, measuring 80–95 cm in length, with a of 150–210 cm and of 3–5 kg, though it retains similar dimorphism patterns with males outweighing females by about 20%. These size variations contribute to ecological partitioning, with the southern often dominating competitive interactions. Key anatomical features include a large, hooked bill with a sharp maxillary unguis adapted for tearing flesh from carcasses or seizing live prey, and prominent salt-excreting nasal glands that enable survival on a marine diet by removing excess salt via concentrated droplets from the nostrils. Giant petrels also possess specialized proventriculi capable of producing energy-rich stomach oil from digested food, which serves as a reserve during periods at sea or for provisioning chicks, and can be regurgitated as a defensive spray against threats.

Plumage Variations

Giant petrels generally display dark brownish-black overall, though the (Macronectes halli) features notably paler underparts, often grey to pale brown-grey and freckled, which become almost white in older individuals. In contrast, the (Macronectes giganteus) has more uniformly dark upperparts and underparts in its predominant form. Adult is glossy, while juveniles exhibit softer, duller feathers that appear more sooty-blackish. The exhibits plumage polymorphism, with a morph accounting for approximately 85% of individuals, characterized by overall grey-brown feathers, and a white morph comprising about 15%, featuring predominantly white head and body accented by black primaries and scattered feathers. The frequency of the white morph varies across colonies, with higher proportions observed in certain populations. The lacks this true polymorphic white form, though some individuals show pale-headed variations. Species-specific differences are also evident in eye and bill coloration, aiding identification. The possesses pale grey to yellow eyes and a paler bill, typically pinkish-yellow with a reddish tip in adults, while the has dark brown eyes in the white morph (pale grey to whitish in the dark morph) and a yellowish-horn bill with a pale green tip. Giant petrels undergo an annual complete molt post-breeding, beginning around during the late incubation or early chick-rearing phase and typically concluding by early winter, with males initiating earlier than females in both species. Juveniles start with duller, more uniform dark that progressively lightens and acquires adult characteristics through successive molts, reaching full adult by 7–13 years; is attained at 6–7 years.

Distribution and Habitat

Breeding Distribution

The Southern giant petrel (Macronectes giganteus) breeds primarily on sub-Antarctic islands and coastal regions of the , with key sites including , the (Islas Malvinas), , , Heard Island, the , and off , as well as numerous locations along the and offshore islands of . Colonies are typically situated in coastal grassy areas, open flats, rocky bluffs, or slopes, allowing for wind-assisted takeoff essential to their large size. Individual colonies can reach up to 10,000 pairs, with the global breeding population estimated at approximately 54,000 pairs as of , showing an increasing trend. The Northern giant petrel (Macronectes halli) has a more northerly breeding distribution, occurring primarily north of the Antarctic Convergence on sub-Antarctic islands such as the Prince Edward Islands (including Marion Island), Crozet Islands, Kerguelen Islands, Macquarie Island, Auckland Islands, Campbell Island, Antipodes Islands, and Snares Islands off New Zealand, as well as South Georgia. Its colonies are generally more dispersed and smaller than those of the Southern species, with maximum sizes up to around 4,300 pairs (e.g., at South Georgia), and the total breeding population estimated at approximately 11,800 pairs as of 2010, showing an increasing trend. Breeding sites show minimal overlap with the Southern giant petrel except at peripheral locations like South Georgia, Marion Island, Crozet Islands, and Macquarie Island, where the two species occur sympatrically but maintain distinct preferences for nesting areas. Both species exhibit strong site fidelity, with established breeders returning annually to the same colonies and nest sites, some of which have persisted for decades or longer. Nests are constructed in open, exposed areas to facilitate takeoff, often on grassy or bare ground near coasts or plateaus. Hybridization between the two species is rare, occurring sporadically at sympatric sites such as and Marion Island, typically involving male Southern and female Northern giant petrels.

Non-breeding Range

During the non-breeding period, giant petrels exhibit distinct dispersal patterns influenced by age and species, with juveniles undertaking extensive post-fledging wanderings while adults generally remain closer to breeding areas. Juveniles of both (Macronectes halli) and (M. giganteus) display nomadic movements, often directed eastward and circumnavigating the , covering distances exceeding 6,000 km within the first three months after fledging in early May. These young birds typically spend 2–5 years at sea before returning to natal colonies, utilizing banding recoveries and satellite tracking to document their wide-ranging paths following prevailing easterly winds and ocean currents. For the Southern Giant Petrel, juveniles disperse northeastward from Antarctic breeding sites, with recoveries concentrated in (57–68%), (17%), (13%), and (5–18%), at average distances of about 8,030 km from natal areas. Adults, in contrast, show limited dispersal, remaining near breeding colonies in the or moving to adjacent pack ice and coastal waters, though some migrate northward to subtropical latitudes off and during winter. Foraging ranges for this species span approximately 40°S to 70°S, tracked via transmitters that reveal concentrations along productive currents and shelf breaks. Non-breeding habitat preferences include pelagic waters, coastal upwellings, and ice edges, with juveniles initially favoring inshore scavenging sites before shifting to more open environments. Vagrancy records document Southern Giant Petrels reaching Australian coasts, though such occurrences are common among juveniles rather than exceptional wanderings. The Northern Giant Petrel follows similar juvenile patterns but with greater variability, where 66% exhibit fully nomadic dispersal and 33% show half-migratory behavior, often extending to subtropical waters off and Africa. Satellite tracking indicates adults forage widely across the from about 20°S to 50°S, typically north of the and following currents such as the for resource-rich areas. Juveniles have been recorded wintering as far north as southern-central (around 15°S), suggesting origins from southwestern Pacific colonies and eastward trajectories. Like their southern counterparts, they prefer pelagic and coastal zones, with occasional use of neritic shelves; rare extends to the North Atlantic. Interspecific overlap intensifies during winter in shared southern latitudes, potentially heightening competition for foraging resources. Adults of both species return annually to breeding sites, while non-breeders and juveniles continue broad oceanic wanderings until .

Behavior and Ecology

Feeding

Giant petrels (Macronectes spp.) primarily consume carrion from seals, , and occasionally whales, supplemented by live prey such as chicks of albatrosses, , and young seals. They opportunistically feed on , , and , with cephalopods and crustaceans forming a larger portion of the diet for females. The (M. giganteus) exhibits more predatory behavior, actively hunting and other seabirds, while the (M. halli) relies more heavily on scavenging, particularly males at seal and colonies. Foraging techniques include , where they steal food from other seabirds, and following fishing vessels to exploit and discarded catch. At carcasses, they adopt the "sealmaster posture"—wings spread, bill agape—to assert dominance and deter competitors. Although primarily surface feeders, they occasionally dive to depths of around 3 meters to access submerged prey. Individuals can consume up to several kilograms in a single meal, processing food into stomach oil that aids . The hunts more actively in waters during breeding, while the forages in subtropical regions, often exploiting garbage patches and fishery waste. As apex , giant petrels clean beaches and coastal areas by consuming carrion, facilitating nutrient cycling in ecosystems. They compete with brown skuas and snowy sheathbills at carcasses, often dominating through aggressive displays. Human activities influence their diet via longline fisheries and , increasing reliance on anthropogenic resources but also elevating mortality risks.

Reproduction

Giant petrels exhibit an annual breeding cycle that is synchronous within colonies, with adults returning to breeding sites in the austral winter or spring depending on the species and location. The (Macronectes halli) typically arrives at colonies in May to July, laying a single egg in mid-August in subantarctic regions like Marion Island, while the (M. giganteus) arrives from July onward, with egg-laying occurring from late September to mid-October in sites such as the Iles Crozet or . Pair bonds are generally long-term and often lifelong, though occasional occurs at rates around 10% in some populations, potentially due to breeding failure or mate incompatibility. rituals include elaborate displays such as sky-pointing, where birds raise their heads and bills toward the sky, and bill fencing, involving mutual clashing of bills while facing each other, which strengthen pair bonds prior to egg-laying. Nests are constructed as low mounds of mud, grass, pebbles, or vegetation, often in loose groups for northern giant petrels or more colonial arrangements for southern giant petrels, with both species showing high site fidelity in subsequent seasons. A single large white egg is laid per pair, weighing approximately 210-260 g for both species, representing a significant energetic investment relative to the female's body mass of 2.5-4.5 kg. Incubation lasts 55-66 days and is shared biparentally, with shifts typically lasting 2-12 days that shorten as hatching approaches; males often contribute around 54% of the effort, and at least one parent remains on the egg at all times to protect against predators and weather. Hatching success varies by site and year but generally ranges from 60-80%, influenced by environmental conditions and nest disturbance. Chick rearing involves intensive biparental care, with the downy chick brooded continuously for 2-3 weeks to maintain body temperature, followed by a guarding phase of 3-5 weeks where one parent remains nearby to deter . After this, chicks are left alone during the day while parents , receiving meals of stomach oil and semi-digested food every 2-3 days, which supports rapid growth to weights exceeding 5 kg before fledging. Fledging occurs 100-130 days post-hatching, with chicks departing slightly earlier (106-120 days) than southern ones; overall fledging success is 50-70%, lower in southern populations due to higher chick mortality from predation or . Post-fledging independence is achieved within 4-6 months, as juveniles disperse to sea without further provisioning. Sexual maturity is reached at 6-10 years, with first breeding typically at 8-10 years, though some individuals may attempt earlier. Due to the high energetic demands of reproduction in harsh and environments, approximately 20-47% of adults skip breeding in any given year to recover condition, particularly after failed attempts.

Social Behavior

Giant petrels are highly territorial, particularly during the breeding season, where they engage in aggressive displays to defend nests and resources. In disputes over food or nesting sites, individuals adopt threat postures such as the forward-threat, involving a squatting position with an arched and fanned , or the upright-threat, with a vertical and head , often escalating to fierce fights featuring interlocked beaks, breast-to-breast grappling, and nape-grasping. These confrontations may include bill jabs and wing-slaps, though injuries are rare due to the birds' thick and skin. Pairs exhibit mutual , involving gentle billing and nibbling of heads and flanks, which strengthens bonds but contrasts sharply with their combative interactions. The species' "stinker" reputation stems from their defensive behavior of regurgitating foul-smelling stomach when threatened, deterring intruders effectively. Group dynamics vary between the two species, with southern giant petrels (Macronectes giganteus) forming loose colonies of 10 to 170 nests, where pairs maintain typical spacing of 3-5 meters between nests, allowing a tolerance of close proximity while minimizing direct conflict. In contrast, northern giant petrels (Macronectes halli) are more solitary breeders, nesting as dispersed pairs often separated by over 5 meters, and only occasionally forming small loose colonies of fewer than 50 pairs. At resource-rich sites like carcasses or near ships discarding , both species aggregate in flocks for kleptoparasitic chases, where dominant individuals displace others to steal , establishing a peck order through aggressive posturing and physical confrontations. Interspecific interactions highlight the giant petrels' dominance as opportunistic predators and , where they often outcompete smaller seabirds for carrion and prey, such as preying on penguin chicks and displacing shearwaters at feeding sites. They frequently compete with skuas over shared resources like unguarded eggs and carcasses, though skuas occasionally kleptoparasitize giant petrels in turn. Rare hybridization occurs at range overlaps, such as at , where northern and southern giant petrels interbreed and back-cross, leading to mixed phenotypes and potential , as documented in long-term studies showing mate fidelity and breeding success in hybrids. Vagrant individuals demonstrate adaptability by surviving in non-native regions far from breeding grounds, occasionally appearing in unexpected northern latitudes. Vocalizations play a key role in social interactions, with giant petrels producing grunting, hissing, and braying calls during disputes to signal and defend territories. These sounds, including guttural snorts from progressing to adult neighing cries, accompany displays and aid in mate attraction through mutual billing sequences. At , individuals remain largely silent, relying on visual cues for coordination rather than vocal communication.

Conservation

Population and Status

The global population of the (Macronectes giganteus) is estimated at approximately 54,000 breeding pairs, equivalent to 95,600–108,000 mature individuals, while the (M. halli) comprises about 11,800 breeding pairs or 23,600 mature individuals. These figures suggest a combined total of roughly 120,000–130,000 mature individuals across both species, with non-breeding birds potentially bringing the total to approximately 200,000–300,000 individuals globally. Both populations have shown increases since the early 2000s, with the exhibiting a 2–3% annual growth rate and the remaining stable to increasing at similar rates. Both species are classified as Least Concern on the , with assessments conducted in 2018 and no significant changes reported by 2025. Regionally, however, conservation statuses vary; in under the Environment Protection and Conservation Act 1999 (EPBC Act), the is listed as Endangered due to historical population declines exceeding 50% in Australian territories, while the is listed as Vulnerable. Population trends indicate recovery from historical declines linked to human activities such as sealing and , which reduced scavenging opportunities and led to direct exploitation; for instance, numbers have benefited from the rebound of populations depleted by sealing. Banding data from the Brazilian Antarctic Program (1984–1993), which ringed over 7,500 Southern Giant Petrel chicks, reveal extensive juvenile dispersal, with recoveries averaging 8,030 km from natal sites and reaching up to 15,268 km, primarily northeastward. Monitoring efforts rely on aerial and ground surveys at key breeding sites to census nests, supplemented by emerging drone-based photogrammetry for non-invasive counts and chick survival assessments. Genetic studies using and markers confirm population connectivity, with ongoing between clades and historical mixing between species, supporting demographic expansions since the Pleistocene. While global populations are increasing, 2025 assessments indicate stable or recovering trends in some managed sites, but significant declines in others; for example, at in the , whole-island counts show the population has halved from over 5,800 nesting birds in the mid-2000s to around 2,600 as of 2025.

Threats and Management

Giant petrels face significant threats from in commercial longline fisheries, particularly in the , where historically an estimated 2,000–4,000 individuals of both were killed annually (1997–1998) in illegal or unregulated operations targeting , though mitigation has reduced rates in legal operations. Historical exploitation during the era also impacted populations, as birds were harvested for food and , while their habit of following ships increases collision risks with vessels. Additionally, disturbances from and past guano mining activities disrupt breeding sites on sub-Antarctic islands. Invasive species such as cats and rats pose a direct threat to chicks on breeding islands, preying on eggs and nestlings and contributing to local population declines. , including plastics, is ingested by giant petrels mistaking debris for prey like or fish, leading to internal injuries, reduced feeding efficiency, and mortality; studies at sites like Marion Island show continued high ingestion rates. Climate change exacerbates vulnerabilities by altering prey availability through sea ice loss and ocean warming, potentially disrupting breeding phenology and foraging success for both northern and southern giant petrels. A 2023 analysis highlighted how receding Antarctic sea ice could reduce food supplies for petrels breeding on nearby islands, with projected range contractions under future warming scenarios. Conservation management focuses on mitigating bycatch through the Agreement on the Conservation of Albatrosses and Petrels (ACAP), which promotes measures like bird-scaring lines (torque lines), night-time bait setting, and weighted branch lines in longline fisheries, significantly reducing seabird mortality where implemented. Protected areas, such as the and established in 2012, safeguard key breeding habitats and regulate fishing activities to minimize interactions. Invasive species eradication programs, including successful rodent and cat removals on islands like Macquarie, have aided population recovery by protecting nesting sites. Australia's national recovery plan for threatened albatrosses and giant petrels includes ongoing monitoring, habitat restoration, and adaptive management to address evolving threats. Post-2020 enhancements in international fishery regulations, including ACAP-guided mitigation in regional organizations, have improved compliance and reduced rates. Recent 2023 studies emphasize building through protected foraging areas, while 2025 assessments indicate stable or recovering populations in some managed sites, though vigilance is required for emerging risks and local declines.

References

  1. https://datazone.birdlife.org/species/factsheet/southern-giant-petrel-macronectes-giganteus
  2. https://datazone.birdlife.org/species/factsheet/northern-giant-petrel-macronectes-halli
  3. https://birdsoftheworld.org/bow/species/norgip1/cur/introduction
  4. https://www.antarctica.gov.au/about-antarctica/animals/flying-birds/petrels-and-shearwaters/southern-giant-petrel/
  5. https://www.marinespecies.org/aphia.php?p=taxdetails&id=206822
  6. https://avibase.bsc-eoc.org/species.jsp?avibaseid=F2812B92
  7. https://avibase.bsc-eoc.org/species.jsp?avibaseid=C1706A8B803AD6EF
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