Antarctic shag

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Antarctic shag
Antarctic Shag with chick at Jougla Point, Antarctica (6063675696).jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Phalacrocoracidae
Genus: Leucocarbo
Species:
L. bransfieldensis
Binomial name
Leucocarbo bransfieldensis
(Murphy, 1936)
Synonyms
  • Phalacrocorax atriceps bransfieldensis
  • Phalacrocorax bransfieldensis

The Antarctic shag (Leucocarbo bransfieldensis), sometimes referred to as the imperial cormorant, king cormorant, imperial shag, blue-eyed shag or Antarctic cormorant, is the only species of the cormorant family found in the Antarctic. [1] It is sometimes considered conspecific with the Imperial shag (Leucocarbo atriceps). [2]

Contents

Description

The adult Antarctic shag is about 75–77 cm tall, [3] has a wingspan of 124 cm, [2] and weighs 1.5-3.5 kg. [4] When looking at individuals within this species, the most defining characteristic is the warty yellow caruncle found on the forehead. [3] Additionally, the blue "eye", which is actually blue skin surrounding the eye, is a distinct trait that stands out. [5] The head, wings, and outside of the thighs are black. [2] While the underparts and central back are white. [4] White is also found on the wing bars that line the upper wing. The bill is dark ranging from brown to yellow. As the bill hooks, the lower mandible becomes lighter. The species has naked pink webbed feet and large black claws. The wings of this species are extremely strong and are powerful in flight with continuous wingbeats disrupted by some gliding. [2] It is estimated that flight speed can reach 50 km per hour. [4]

Juveniles are duller and browner than adults. They don't usually have the warty caruncle or white patch on their back. [2]

Males and female look very similar but can be distinguished by size. Males are larger than females in size and are also larger-billed. [2]

Taxonomy

The Antarctic shag is part of the order Suliformes and the family Phalacrocoracidae, which includes all cormorants and shags. Still, there are some taxonomic issues regarding the species. The Antarctic shag is usually placed in genus Phalacrocorax or Leucocarbo . [3] This species is one of the blue-eyed shags, however its position within the group is debated. [6] Some scientists lump the Antarctic shag with other species, such as the imperial shag. [2] However, the IOC World Bird List and the Clements Checklist consider the Antarctic shag to be its own species. [7]

Habitat and Distribution

Currently, the Antarctic shag is found on the Antarctic Peninsula, South Shetland Islands, and Elephant Island. [3]

The Antarctic shag is described as a marine species staying near the shores of coastal regions and some islands. [3] Additionally, colonies are usually found near packed ice. During the breeding season, breeding colonies are found on cliffs, rocky slopes, outcrops and sometimes even flat coasts or islets. [2]

This species is sedentary and doesn't migrate. However, a single Antarctic shag was found dead in Bahia, Brazil in 2002; it had previously been ringed in the South Shetland Islands. [8] [9] Colonies may move short distances to find waters that aren't frozen in order to feed. This short move most likely occurs during winter months when ice starts to spread and cover the ocean where the birds feed. [3]

Population Status

The current population of the Antarctic shag is stable, [3] with a estimated 20,000 individuals worldwide. [4] Currently there is no particular threat that could hurt the community or population size. [3]

It is very hard to estimate the population of species in isolated areas, such as the Antarctic. Still, recent studies using Unmanned Aerial Vehicles (UAV) have allowed scientists to estimate Antarctic shag populations by taking images of colonies. Since this data is based on images, more can also be learned about topography, habitat selection and nesting. In the future, this might allow scientists to more precisely estimate population size. [10]

In 2018, a study found that 3.5% of the global Antarctic shag population breeds in Ryder Bay. [11] The study also calls for greater protections of the area.

Behavior

Reproduction

Antarctic shags are monogamous and only mate with one partner each nesting season. Still, partners may change between seasons. Males attract breeding partners with a greeting display. [2]

Typically, colonies breed on low rocky cliffs near the water. [2] Sometimes, breeding colonies are shared with other bird species such as the rock shag, southern rockhopper penguin, and black-browed albatrosses. [4] This species usually forms smaller colonies of 20-40 pairs, but larger colonies of up to 800 pairs have been observed. [3]

Both genders build a nest from feathers, seaweed, and ocean debris. Materials are then connected with excreta, [2] which is waste material, such as feces and urine. [12] Shag mating pairs often steal nesting material from other couples. [4] The final nest shape looks like a cone with the tip cut off, similar to a volcano. [4] Nests are sometimes reused between years as many individuals return to the same breeding site. [3]

Antarctic shags lay their eggs between October and December. The female lays 2 or 3 eggs on average; [2] but up to 5 eggs have been observed. [4] Both parents help incubate the eggs for 28–31 days. [2] Chicks hatch without a protective down making them vulnerable to the Antarctic conditions. Due to this lack of protection, parents must keep their chicks warm for the first few weeks. [4] The naked chicks are fed by their parents for about 3 weeks with the male partner providing most of the food. After about 3 weeks, the chicks start to fledge. [2] By age 4, the offspring will have reached sexual maturity. [3] The Antarctic shag has an estimated life expectancy of 15–20 years in the wild. [4]

Breeding success can be directly affected by food availability [3] and diving conditions. [13]

Diet

The most common way to study the Antarctic shag's diet is by analyzing its pellets. [14] Their pellets are often composed of bones, fur and feathers.

Antarctic shags usually forage alone or in small groups. [4] [2] Most of the Antarctic shag's diet is composed of fish, [13] but can also include crustaceans, octopuses, snails, worms, slugs and other invertebrates. [4] The fish diet is mostly composed of humphead notothen (Gobionotothen gibberifrons), gaudy notothen (Lepidonotothen nudifrons), bullhead notothen (Notothenia coriiceps), and Antarctic spiny plunderfish (Harpagifer antarcticus). [13] Typically, the females consume more invertebrates while the males consume more fish. [15] This difference in diet is most likely due to the difference in size of each gender. [14]

Role in the food web

Antarctic shags are rarely prey for other species. There have been a few documented cases, including leopard seals and brown skuas killing Antarctic shags. However, other bird species prey on their eggs and chicks as well. [15]

Unlike other birds, the Antarctic shag consumes demersal fish. [15] In fact, this species can reach extreme depths when diving for their food. [2] Since demersal fish are found on the ocean floor, these fish feed on other benthic species. [16] Thus, the Antarctic shag links the benthic and pelagic zones of the food web. Despite linking these two areas of the ocean, the Antarctic shag has a limited population. Therefore, the amount of demersal species consumed doesn't impact the entire ecosystem. [15]

Diving

On average, the Antarctic shag dives 25 meters to feed on fish. [2] Their maximum dive depth is around 60 meters. [4] The number of dives and depth of each dive is related to foraging conditions. They most likely ingest smaller fish and invertebrates while underwater. In contrast, larger fish, 15 cm or longer, are brought to land to eat. [13]

Shags can't predict how much time is required to dive and capture prey. Once underwater, the bird looks for prey, and reacts based on the situation. If a fish is found but the shag doesn't have enough oxygen, it will come back up to the surface, take in the largest amount of air possible, and dive again to capture the prey. This shows that the Antarctic shag changes its diving strategy based on the situation. [13]

Many birds can't fly with wet feathers and diving in the water can cause feathers to become waterlogged (fully saturated). Often, you see waterbirds standing with their wings spread to dry off their feathers after diving. [17] Antarctic shags are unique in this respect and due to their dense inner plumage, this species doesn't need to dry off via wing-spreading like other diving bird species. [2] These dense feathers close to the skin also prevent icy waters from hitting the skin. Additionally, birds having to spread their wings to dry could have further reduced their body temperature in an already extremely harsh climate. Therefore, both the cold water and cold air could have caused this species to develop over time. [18]

Vocalization

Shags are known to be quiet but often vocalize at breeding sites or when vulnerable. [19] When threatened, the male makes a "aaark" call while the female will make a hissing call. [2] In contrast, during breeding, males makes a "honk" call. [2]

Related Research Articles

<span class="mw-page-title-main">Cormorant</span> Family of aquatic birds

Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the International Ornithologists' Union (IOU) adopted a consensus taxonomy of seven genera. The great cormorant and the common shag are the only two species of the family commonly encountered in Britain and Ireland and "cormorant" and "shag" appellations have been later assigned to different species in the family somewhat haphazardly.

<span class="mw-page-title-main">Great cormorant</span> Species of bird

The great cormorant, known as the black shag or kawau in New Zealand, formerly also known as the great black cormorant across the Northern Hemisphere, the black cormorant in Australia, and the large cormorant in India, is a widespread member of the cormorant family of seabirds. The genus name is Latinised Ancient Greek, from φαλακρός and κόραξ, and carbo is Latin for "charcoal".

<span class="mw-page-title-main">European shag</span> Species of bird

The European shag or common shag is a species of cormorant. It is the only member of the monotypic genus Gulosus. It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainly wintering in its breeding range except for the northernmost birds. In Britain this seabird is usually referred to as simply the shag. The scientific genus name derives from the Latin for glutton. The species name aristotelis commemorates the Greek philosopher Aristotle.

<span class="mw-page-title-main">Australian pied cormorant</span> Species of bird

The Australian pied cormorant, also known as the pied cormorant, pied shag, or great pied cormorant, is a medium-sized member of the cormorant family. It is found around the coasts of Australasia. In New Zealand, it is usually known either as the pied shag or by its Māori name of kāruhiruhi. Older sources may refer to it as the "yellow-faced cormorant".

<span class="mw-page-title-main">Spotted shag</span> Species of bird

The spotted shag or pārekareka is a species of cormorant endemic to New Zealand. Though originally classified as Phalacrocorax punctatus, it is sufficiently different in appearance from typical members of that genus that for a time it was placed in a separate genus, Stictocarbo, along with a similar species, the Pitt shag. Subsequent genetic studies show that the spotted shag's lineage is nested within the typical shags.

<span class="mw-page-title-main">Flightless cormorant</span> Species of flightless bird endemic to the Galapagos islands

The flightless cormorant, also known as the Galapagos cormorant, is a cormorant endemic to the Galapagos Islands, and an example of the highly unusual fauna there. It is unique in that it is the only known cormorant that has lost the ability to fly. It was placed in its own genus, Nannopterum, but then was later placed with most of the other cormorants in the genus Phalacrocorax. A 2014 study supported reclassifying it and two other American cormorant species back into Nannopterum. The IOC followed this classification in 2021.

<span class="mw-page-title-main">Guanay cormorant</span> Species of bird

The guanay cormorant or guanay shag is a member of the cormorant family found on the Pacific coast of Peru and northern Chile. After breeding it spreads south to southern parts of Chile and north to Ecuador, and has also been recorded as far north as Panama and Colombia – probably a result of mass dispersal due to food shortage in El Niño years. Its major habitats include shallow seawater and rocky shores.

<span class="mw-page-title-main">Cape cormorant</span> Species of bird

The Cape cormorant or Cape shag is a bird endemic to the southwestern coasts of Africa.

<span class="mw-page-title-main">Rock shag</span> Species of bird

The rock shag, also known as the Magellanic cormorant, is a marine cormorant found around the southernmost coasts of South America. Its breeding range is from around Valdivia, Chile, south to Cape Horn and Tierra del Fuego, and north to Punta Tombo in Argentina. In winter it is seen further north, with individuals reaching as far as Santiago, Chile on the west coast and Uruguay on the east. The birds also breed around the coasts of the Falkland Islands.

<span class="mw-page-title-main">Black-faced cormorant</span> Species of bird

The black-faced cormorant, also known as the black-faced shag, is a medium-sized member of the cormorant family. Upperparts, including facial skin and bill, are black, with white underparts. It is endemic to coastal regions of southern Australia.

<span class="mw-page-title-main">Auckland shag</span> Species of bird

The Auckland shag or Auckland Islands shag is a species of cormorant from New Zealand. The species is endemic to the Auckland Islands archipelago. It is a sedentary bird that primarily eats various crustaceans and fish. In recent years, roughly 1,000 pairs have been recorded. The Auckland shag is a colonial nester, building sizeable nests of, among other items, grass, twigs and seaweed. The Auckland shag lays three pale blue-green eggs in November–February. The incubation period is 26–32 days.

<span class="mw-page-title-main">Imperial shag</span> Species of bird

The imperial shag or imperial cormorant is a black and white cormorant native to southern South America, primarily in rocky coastal regions, but locally also at large inland lakes. Some taxonomic authorities, including the International Ornithologists' Union, place it in the genus Leucocarbo, others in the genus Phalacrocorax. It is also known as the blue-eyed shag, blue-eyed cormorant and by many other names, and is one of a larger group of cormorants called blue-eyed shags. The taxonomy is very complex, and several former subspecies are often considered separate species.

<span class="mw-page-title-main">Red-legged cormorant</span> Species of bird

The red-legged cormorant, also known as the red-legged shag, red-footed cormorant, red-footed shag, Gaimard's cormorant and grey cormorant, is a species of cormorant resident to the coastline of South America. It is the only member of the genus Poikilocarbo. It is non-colonial unlike most seabirds. The red-legged cormorant has not been observed wing-spreading, which is unusual among cormorant species.

<span class="mw-page-title-main">Chatham shag</span> Species of bird

The Chatham shag, also known as the Chatham Island shag, is a species of bird in the cormorant and shag family, Phalacrocoracidae. It is endemic to the Chatham Islands of New Zealand. For a long time the species was placed in the genus Phalacrocorax; today it is mostly placed with the other blue-eyed shags of New Zealand and Antarctica in the genus Leucocarbo. Its closest relative is the Otago shag of South Island.

<span class="mw-page-title-main">Bounty shag</span> Species of bird

The Bounty shag, also known as the Bounty Island shag, is a species of cormorant of the family Phalacrocoracidae. They are found only on the tiny and remote Subantarctic Bounty Islands, 670 km southeast of New Zealand. Its natural habitats are open seas and rocky shores. In 2022, a full Unmanned aerial vehicle survey of the Bounty archipelago found a total of 573 breeding pairs and estimates the population to consist of approximately 1,733 birds. These recent estimates are consistent with the only other comparable study from 1978 and suggest that the species' population has remained stable over the past 45 years.

<span class="mw-page-title-main">Kerguelen shag</span> Species of bird

The Kerguelen shag is a species of cormorant endemic to the Kerguelen Islands in the southern Indian Ocean, one of the most isolated places on Earth. Many authorities consider it a subspecies of the imperial shag.

<span class="mw-page-title-main">South Georgia shag</span> A species of bird

The South Georgia shag, also known as the South Georgia cormorant, is a marine cormorant native to South Georgia and a few other subantarctic islands in the South Atlantic Ocean.

The Heard Island shag, or Heard Island cormorant, is a marine cormorant native to the Australian territory comprising the Heard and McDonald Islands in the Southern Ocean, about 4100 km south-west of Perth, Western Australia.

<span class="mw-page-title-main">Macquarie shag</span> Species of cormorant

The Macquarie shag, Macquarie Island shag or Macquarie Island cormorant, is a marine cormorant native to Macquarie Island in the Southern Ocean, about halfway between Australia and Antarctica.

<span class="mw-page-title-main">Crozet shag</span> Species of bird

The Crozet shag, also known as the South Georgia cormorant, is a marine cormorant native to the Crozet, Prince Edward and Marion islands in the South Atlantic Ocean.

References

  1. ↑ "The Antarctic Shag". Wildfoot Travel Journal. 2016-05-02. Retrieved 2020-10-14.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 "Antarctic Shag". www.oiseaux-birds.com. Retrieved 2020-10-09.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 "Birds of the World - Comprehensive life histories for all bird species and families". birdsoftheworld.org. Retrieved 2020-10-09.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 "Blue-eyed shag". oceanwide-expeditions.com. Retrieved 2020-10-10.
  5. ↑ "Blue Eyed Shag / Imperial Shag, Antarctica fact file birds". www.coolantarctica.com. Retrieved 2020-10-14.
  6. ↑ Nelson, Bryan, 1932- (2005). Pelicans, cormorants and their relatives : Pelecanidae, Sulidae, Phalacrocoracidae, Anhingidae, Fregatidae, Phaethontidae. Oxford: Oxford University Press. ISBN   1-4237-6812-4. OCLC   67291699.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  7. ↑ "Leucocarbo bransfieldensis (Antarctic Shag) - Avibase". avibase.bsc-eoc.org. Retrieved 2020-11-02.
  8. ↑ Lima, P.C.; Grantsau, R; Lima, R.C.F.R; dos Santos, S.S. (2002). "Notas sobre os registros brasileiros de Calonectris edwardsii (Oustalet, 1883) e Pelagodroma marina hypoleuca (Mouquin-Tandon, 1841) e primeiro registro de Phalacrocorax bransfieldensis (Murphy, 1936) para o Brasil". Ararajuba. 10 (2): 263–265.
  9. ↑ Orta, Jaume; Garcia, Ernest; Christie, David; Jutglar, Francesc; Kirwan, Guy M. (2020-03-04), Billerman, Shawn M.; Keeney, Brooke K.; Rodewald, Paul G.; Schulenberg, Thomas S. (eds.), "Antarctic Shag (Phalacrocorax bransfieldensis)", Birds of the World, Cornell Lab of Ornithology, doi:10.2173/bow.antsha1.01, S2CID   243014094 , retrieved 2020-11-02
  10. ↑ Oosthuizen, W. Chris; Krüger, Lucas; Jouanneau, William; Lowther, Andrew D. (2020-01-02). "Unmanned aerial vehicle (UAV) survey of the Antarctic shag (Leucocarbo bransfieldensis) breeding colony at Harmony Point, Nelson Island, South Shetland Islands". Polar Biology. 43 (2): 187–191. doi:10.1007/s00300-019-02616-y. hdl: 2263/76501 . ISSN   0722-4060. S2CID   209528444.
  11. ↑ "Seabird populations on Antarctic Peninsula unexpected". phys.org. Retrieved 2020-11-02.
  12. ↑ "EXCRETA | meaning in the Cambridge English Dictionary". dictionary.cambridge.org. Retrieved 2020-10-13.
  13. 1 2 3 4 5 Casaux, Ricardo (December 2004). "Diving Patterns in the Antarctic Shag". Waterbirds. 27 (4): 382–387. doi:10.1675/1524-4695(2004)027[0382:DPITAS]2.0.CO;2. hdl: 11336/29062 . ISSN   1524-4695. S2CID   85908033.
  14. 1 2 Casaux, Ricardo. "On The Accuracy of the Pellet Analysis Method to Estimate The Food Intake in the Antarctic Shag, Phalacrocoraz bransfieldensis". Folia Zool. 52: 167–176 – via Researchgate.
  15. 1 2 3 4 Casaux, Ricardo; Barrera-Oro, Esteban (March 2006). "Shags in Antarctica: their feeding behaviour and ecological role in the marine food web". Antarctic Science. 18 (1): 3–14. Bibcode:2006AntSc..18....3C. doi:10.1017/s0954102006000010. hdl: 11336/102295 . ISSN   0954-1020. S2CID   86322485.
  16. ↑ "Demersal Fish | Tethys". tethys.pnnl.gov. Retrieved 2020-10-09.
  17. ↑ Thompson, Mya (2013-08-08). "Double-crested Cormorant Dries its Feathers | Bird Academy • The Cornell Lab". academy.allaboutbirds.org. Retrieved 2020-10-13.
  18. ↑ Neil, Bernstein; Maxson, Stephen (1982). "Absence of Wing-spreading Behavior in the Antarctic Blue-Eyed Shag (Phalacrocorax atriceps bransfieldenis". The Auk. 99 (3): 588–589 – via JSTOR.
  19. ↑ Parmlee, David (1980). Bird Island in Antarctic Waters. University of Minnesota Press.
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