The Heard Island shag (''Leucocarbo nivalis''), or Heard Island cormorant, is a marine
cormorant
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 IOC adopted a consensus taxonomy of seven ge ...
native to the
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
n territory comprising the
Heard and McDonald Islands
The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size ...
in the
Southern Ocean, about 4100 km south-west of
Perth,
Western Australia.
Taxonomy
The Heard Island shag is one of the
blue-eyed shags, sometimes placed in the
genus ''Leucocarbo'', and a
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
of the
imperial shag. Others place it in the genus
Phalacrocorax
''Phalacrocorax'' is a genus of fish-eating birds in the cormorant family Phalacrocoracidae. Members of this genus are also known as the Old World cormorants.
Taxonomy
The genus ''Phalacrocorax'' was introduced by the French zoologist Mathurin ...
. It is now usually considered to be a full species.
Distribution and habitat
The Heard Island shag is restricted to the
subantarctic Heard and
McDonald Islands, and is only known to breed on Heard Island. Apart from breeding and roosting, its
habitat is marine.
Description
The Heard Island shag has largely black upperparts and white underparts. The cheeks and ear-coverts are white; there are white bars on the wings, a black, recurved crest over the forehead, and pink feet.
[Marchant & Higgins (1991), p.854.] A breeding adult has a pair of orange
caruncles above the base of the
bill in front of the eyes as well as blue eye-rings.
It is about 77 cm in length, with a
wingspan of 120 cm and a weight of 3 kg.
Behaviour
Heard Island shags are gregarious, roosting in groups of from 10-20 birds up to several hundred.
Breeding
The birds are present year round at Heard Island, where they breed annually in
colonies. Courtship takes place from late August to early October. Nests are mounds built largely of the
stipes
Crucifixion is a method of capital punishment in which the victim is tied or nailed to a large wooden cross or beam and left to hang until eventual death from exhaustion and asphyxiation. It was used as a punishment by the Persians, Carthagin ...
,
roots and adhering soil of the
tussock grass ''
Poa cookii
''Poa cookii'', sometimes called Cook's tussock-grass or bluegrass, is a species of tussock grass native to various subantarctic islands. The specific epithet honours British explorer James Cook who visited the Kerguelen Islands in 1776.
Desc ...
'' and average about 22 cm high, with a minimum distance between nests of 50 cm. The clutch of two or three eggs is laid mainly between mid-September and November, hatching from November to February. The chicks
fledge
Fledging is the stage in a flying animal's life between hatching or birth and becoming capable of flight.
This term is most frequently applied to birds, but is also used for bats. For altricial birds, those that spend more time in vulnerable c ...
from January to March.
[DEWHA website]
Feeding
The birds forage locally in shallow coastal waters,
with the diet consisting primarily of
polychaetes and
fish.
[Green, K., and Williams, R. (1997). ''Biology of the Heard Island Shag Phalacrocorax nivalis. 3. Foraging, Diet and Diving Behaviour.'' Emu 97: 76-83] The proportion of fish in the diet is higher when the birds are feeding chicks.
Status and conservation
The Heard Island shag population is estimated to comprise about 1000 breeding pairs. It is listed as
Vulnerable
Vulnerable may refer to:
General
* Vulnerability
* Vulnerability (computing)
* Vulnerable adult
* Vulnerable species
Music
Albums
* ''Vulnerable'' (Marvin Gaye album), 1997
* ''Vulnerable'' (Tricky album), 2003
* ''Vulnerable'' (The Used album) ...
under Australia's
Environment Protection and Biodiversity Conservation Act 1999,
because the population is small, localised and subject to fluctuations in breeding success due to weather conditions and food availability. A potential threat is
climate change affecting sea temperatures and thus food supply.
[Garnett & Crowley (2000).]
Notes
References
*
*
*
*
*
*
*
*
{{Taxonbar, from=Q1261443
Heard Island shag
Fauna of Heard Island and McDonald Islands
Heard Island shag
Heard Island shag
Birds of Australia