Heard Shag
Leucocarbo nivalis
Suliformes Order – Phalacrocoracidae Family
INTRODUCTION:
The Heard Shag is sometimes considered a subspecies of the Imperial Shag. It is included in the group of “blue-eyed shags” and placed in the genus Leucocarbo. This species is endemic to Heard Island.
DESCRIPTION OF THE BIRD:
Biometrics:
Length: 77 cm
Wingspan: 120 cm
Weight: 2800-3300 g
The adult is black and white. In breeding plumage, top, head sides and hindneck are glossy black, with black crest on the forehead. Some white filoplumes are visible above and behind the eye where they can form small tufts, and others are scattered on head, neck and back.
On the upperwing, wing-coverts are blackish-brown with green gloss. We can see a large white wingbar formed by lesser and some median upperwing coverts. On the upperparts, the back is black with white patch between the posterior bases of the wings. The rump is black and the tail too, the latter with white shaft bases.
On the underparts, the body is white, contrasting with blackish underwing. There is a variable white bar along the basal leading edge.
The bill is greyish-black with paler tip on lower mandible. There are two conspicuous orange caruncles on the upper base of the bill, in front of the eyes which are dark brown, surrounded by blue eyering. Legs and webbed feet are bright pink.
In non-breeding plumage, the caruncles are duller, mostly yellowish. The crest is much reduced or lost. The plumage is less glossy and lacks the filoplumes.
Both sexes are similar.
The juvenile has dark brown upperparts with variable white wing patch. It lacks the caruncles, and the bare parts are duller than on adults.
RANGE:
The Heard Shag is restricted to Heard Island in SE Indian Ocean.
HABITAT:
The Heard Shag is marine. It forages inshore in coastal shallow waters. It breeds on sea-facing cliff tops on offshore stacks, and at edges of lava cliffs among tussock grass (Poa cookie) and moss (Azorella). The breeding colonies can be established on flat ground or on steep vegetated slopes, or on cliffs. They roost in similar habitats.
CALLS AND SONGS:
The Heard Shag male gives loud barking calls and honks, whereas the female usually hisses.
BEHAVIOUR IN THE WILD:
The Heard Shag feeds mainly on marine worms and fish, and may take occasionally squid and other molluscs, according to the site and the season.
It forages in shallow water by pursuit-diving. They may form small feeding flocks.
The Heard Shag is gregarious at roosts and when feeding. They breed in colonies.
The male usually displays at nest-site to attract a female. It performs typical displays such as “wing-waving” with raised wings, “bill-pointing” to expose the bright-coloured bare parts, and “gargling” with the nape touching the rump while producing a special call.
The Heard Shag is sedentary and remains on Heard Island where it only performs internal movements from colonies to roosts.
The flight is powerful with continuous wingbeats and occasional glides.
REPRODUCTION OF THIS SPECIES:
The laying occurs in October/November.
The Heard Shag breeds in small colonies. The typical nest is a truncated cone made with grass, and compacted with mud and excreta. It is placed in tussock grass on cliff.
The female lays 2-4 blue-green eggs. The incubation lasts about one month (29-32 days) and is shared by both adults which take regular stints. The chicks are fed with fish by their parents. They fledge 55 days after hatching.
PROTECTION / THREATS / STATUS:
The Heard Shag has restricted range on a single island. Heard Island is predator free, so this threat is absent. However, this species is vulnerable to severe weather conditions, but also to commercial fishing operations around the island.
This species is considered as Near Threatened. It is present at only one site and has small population estimated at 2,200 mature individuals.
Fr: Cormoran de Heard
All: Heardscharbe
Esp: Cormorán de la Heard
Ita: Cormorano di Heard
Nd: Heardaalscholver
Sd: Heardskarv
Text by Nicole Bouglouan
Sources:
HANDBOOK OF THE BIRDS OF THE WORLD vol 1 by Josep del Hoyo-Andrew Elliot-Jordi Sargatal - Lynx Edicions - ISBN: 8487334105
BirdLife International (BirdLife International)
Department of Sustainability, Environment, Water, Population and Communities
Wikipedia, the free encyclopaedia