Oceanic islands are incredibly important as breeding platforms for hosts of seabirds, where they are protected from the threats of mammalian predators and human disturbance. In turn the birds supply nutrients from the oceans to these islands in the form of guano, egg shells, feathers and carcasses. In dense colonies such as those of the penguins these nutrients are washed out to sea, stimulating plankton growth which forms the basis of the marine food web on which the breeding birds rely. Seabirds are also often the transporters of seeds and small insects to the islands, increasing the complexity and diversity of the ecosystem. There is thus a tight dependence between bird and island, and vice-versa.
Of the sub-Antarctic islands, the Prince Edward Island group (which includes Marion Island) is the second most important in terms of number of species of breeding birds. In addition, they contain some of the largest bird colonies in the world, such as the King Penguin colony at Kildalkey Bay. Twenty nine species of birds use the islands for breeding and moulting, only one of which is a true land bird. All of these birds are indigenous, and although none are endemic there are significant genetic differences between the populations of some species on the island and those elsewhere.Vagrants, which stay for short periods and do not breed on the island, are frequently recorded. There are currently no introduced species, although chickens, geese and parrots have at various times been kept at the base.





Penguins

King (Aptenodytes patagonicus)

The King is the largest penguin on Marion, standing almost a metre high. They breed in large colonies on pebble beaches, incubating the egg and brooding the chick on their feet. Eggs are laid from November to March, incubated for 55 days, and the chicks are reared for ten to thirteen months. Due to the long incubation and rearing period most birds will only breed twice in three years. The birds moult between September and March. The King feeds mainly on fish, foraging up to 300km from the Island. The Marion population is the second most important in the world, and is estimated at 215 000 breeding adults.



Gentoo(Pygoscelis papua)

The rarest penguin on the island, with a population of just over 1 000 breeding adults, the Gentoo is also the most sensitive to human disturbance. It breeds in winter in more inland vegetated areas, laying eggs in July and rearing the chicks until December. The adults moult after breeding and then leave the island. The Gentoo feeds 15-40km from shore, preying mainly on krill and fish.

Macaroni(Eudyptes chrysolophus)

The Macaroni is the larger of the two crested penguins found on Marion Island. It breeds in large colonies on the sheltered east coast, usually high up on slopes in grey lava. The Marion breeding population is estimated at 398 000. Breeding starts near the end of October, and the chicks fledge near the end of February. The Macaroni feeds mainly on crustaceans, but also preys cephalopods and fish.


Rockhopper(Eudyptes chrysocome)

Breeding in rocky areas all around the coast, the Marion populationsis estimated at 173 000 adults. Breeding starts in mid-November and chicks fledge late February. The birds moult after breeding and the last adults have left the colonies by mid-March. Rockies feed mainly on crustaceans but also takes some squid and fish.

Albatrosses

Wandering(Diomedea exulans)

The Wandering Albatross is perhaps most well-known for its massive wingspan (up to 3.5m) and the vast distances it covers while at sea (up to 900km a day). As their breeding season lasts eleven months (from December/January until November) they usually only breed every second year, returning to the same site and pairing with the same mate for life. The annual breeding population at Marion Island consists of 1500 birds. This population is under threat from longline fishing as Wanderers are great scavengers, feeding on bait and offal from fishing boats, as well as their normal squid and fish prey.

Greyheaded(Thalassarche chrysostoma)

Sooty(Phoebetria fusca)

Lightmantled(Phoebetria palpebrata)

The Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) is only found on Prince Edward Island.

Petrels and Prions

Salvin's Prion (Pachyptila salvini)
Fairy Prion (Pachyptila turtur)
Blue (Halobaena caerulea)
Greatwinged (Pterodroma macroptera)
Kerguelen (Lugensa brevirostris)
Softplumaged (Pterodroma mollis)
Grey (Procellaria cinerea)
Whitechinned (Procellaria aequinoctialis)
Blackbellied Storm (Fregetta tropica)
Greybacked Storm (Garrodia nereis)
South Georgia Diving (Pelecanoides georgicus)
Northern Giant (Macronectes halli)
Southern Giant (Macronectes giganticus)

Others

Sub-antarctic Skua (Catharacta antarctica)
Kelp Gull (Larus dominicanus)
Lesser Sheathbill (Chionis minor marionesis)
Imperial Cormorant (Phalacrocorax atriceps)
Antarctic Tern (Sterna vittata)
Kerguelen Tern (Sterna virgata)

Vagrants

Vagrant species most commonly sighted: European Swallow (Hirondu rustica), Cattle egret (Bubulcus ibis)

Alien introductions

Past introductions of birds include chickens. Only some of the ruins of the old chicken run is still on the island and these days very strict control is exercised when it comes to any poultry produce.