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Sheathbills, Skuas and Stinkers

The Bad Boys of Antarctica’s Avifauna

Each time I work in Antarctica, I am often saddened to hear groans of disgust when people see their first predators or scavengers like Sheathbills, Skuas or Stinkers (Giant Petrels).  Their reputations as “chick stealers”, “poo eaters”, “carcass lovers” and their collective reputations of evil echo that of many mainland scavengers and predators.  Through their natures, smells, behaviour and appearances, they become more difficult to love somehow, more “ugly” than other birds like penguins who are considered “cute” or albatrosses who are considered “majestic”.

Yet each of these birds performs a vital role in seabird ecology and after many years of working with them as a seabird handler and guide, I have found that even the most unloveable species of seabird in the Southern Ocean have loveable sides.

Here are some dark and light sides to some of Antarctica’s iconic avifauna.

Sheathbills (The Poo Eaters) Family: Chionidae

“You are the first birder I’ve ever met who has seen a Black-faced Sheathbill ahead of the White-faced in my life” mentioned my partner, Mark, at the end of our recent trip to Antarctica.  We met on the only island in the world where the Black-faced Sheathbill exists, in the isolated, remote Australian Antarctic territory of Heard Island, deep in the southern Indian Ocean.

The Dark Side

Irrespective of their facial markings, Sheathbills share a rather common and disturbing trait of coprophagia or eating both their own faeces and that of other animals.  Their diets have also incorporated tape worms extracted from the stomachs of penguins, leftovers from any carcasses remaining on the beach, placenta or afterbirth of seals and penguins, kelp, invertebrates and even leftover food from penguins.  On some occasions Sheathbills have been known to attack other birds for food but scavenging is definitely their preferred method of getting their next meal.

The Light Side

Sheathbills are often called “Antarctic Chickens” for their white appearance and their propensity to walk across the ground, rather than fly.  On my most recent trip to Antarctica I was surprised to watch one follow our boat for over an hour way out to sea.  I wondered where it was heading!  The long open sea flight proved to be a big burden on this robust little bird, to the point it occasionally sought a place on the decks of our boat to rest.

On Heard Island I loved watching Sheathbills inspect our backpacks for tidbits and take shelter from the wind behind our dry barrels on the black sand beaches.  They sometimes also followed us around like small puppies.

After becoming acquainted with both species of Sheathbills on Heard Island and also recently on South Georgia, I tend to see them as comical rather than marauding scavengers of the worst kind.  They look like chickens, act like chickens and yet they are tough little birds who have become incredibly resourceful to survive in some of the harshest environments on earth.

Skuas (The Machiavellis of Antarctica) Family: Stercorariidae

Of all the birds I’ve worked with the Skua family is perhaps the only bird I will hesitate to hold during research.  As distant relatives of Gulls; Skuas, and Brown Skuas in particular, have a wicked glint in their eye that gives them an appearance of wanting to kill you.  On more than one occasion I’ve seen a Brown Skua bite a handler on release, not because it has been handled badly, but simply out of spite.

The Dark Side

Skuas are the Machiavellis of the world’s polar regions.  I’ve watched them sneak up on penguin nests to steal their eggs for food, round up unsupervised penguin chicks and herd them off ledges to stun them before eating them, bash their way into a carcass feeding session, fearlessly taking on the Giant Petrels already present in order to get a side meal and also harangue other seabirds in flight to either catch them or make them vomit food up out of panic (in ways similar to Frigatebirds) so they can eat it.

On my recent trip to the Antarctic continent, I was lucky enough to watch a Brown Skua play with its stolen Gentoo Penguin egg in the snow, a bit like a cat plays with its prey before it eats it.  It was a fascinating encounter, even though it spelled the end of a Gentoo Penguin, watching this bird struggle to pick up his egg as it rolled down a snowy slope.  Finally it was joined by its partner to share in the feast.

Penguins are quite fearful of Skuas for good reason.  On Macquarie Island, the most successful Gentoo Penguin nests are the ones located around the buildings of the research base.  Gentoos have learned that Skuas don’t like people and the feeling is mutual so their chicks are safer from predation, simply because more humans are present around the base.

Utilising a wicked combination of a sharp bill, alongside reptilian feet that are a weird evolutionary cross between webbing (for swimming) and talons (for hunting), it’s needless to say Skuas are not the most loved birds in the world.

The Light Side

Yet from a distance I actually quite like Skuas.  I’ve watched Brown Skuas perform the most stunning aerial acrobatics trying to catch food when I’ve been at sea. I’ve also watched Pomarine Skuas performing similar acrobatics when they’ve tried to grab bits of caribou fur from living caribou to line their nests.  All of these manoeuvres are performed with wings in the air and mouths open in a display of dramatic behaviour that would rival any theatre act.

They are completely fearless.  Up close they actually have bloodshot eyes which make them look like they have a grumpy appearance after a hard night on the town.  Skuas don’t care about the size of the competitor, they will fight it regardless, be it another bird, caribou, seal or even a human.

The inside of a Brown Skua’s mouth is actually baby pink.

When Skua couples meet they greet each other with a wonderful display of wings in the air, mouths open, calling and biting each other.  It may sound like rough love to some but for Skuas this is true love and it’s wonderful to watch.

Stinkers or Giant Petrels (The Boofheads) Family: Procellaridae

Giant Petrels sadly have probably the worst reputation of Antarctica’s predator and scavenger birds and of all three bird families, they are perhaps the birds I like the most.

On a very superficial level, Giant Petrels do look ugly to a lot of people.  The gigantic nasal tube that crowns their bills only adds to their overall thumping appearance of heavy, unwieldy on the ground and argumentative persona.

The Dark Side

Giant Petrels are the carcass kings of Antarctica.  If there is a dead penguin or seal to be feasted upon, they are the very first birds there and when they arrive, they don’t just pick around the edges of a dead animal, they plunge head first into the feast, often emerging with a face full of blood or sinew.

Couple that with frequent arguments against other Giant Petrels and a propensity to feast off a carcass with their wings wide spread to insert their dominance over their meal and usually people will walk past them in disgust.

The Light Side

Did you know that Giant Petrels smell like old library books?  I think a lot of people imagine them to be perfumed with a disgusting combination of carcass and fish but in reality it’s quite the opposite.  They actually smell of a familiar mustiness and leathery aroma that is very evocative of old books or old desks.  It is more pleasing than you think.

Their plumage is actually very beautiful.  Up close each of their breast feathers are rounded with a slightly pointed tip, making each look like a tear drop.  Their feathers are also very subtly marked with striped vermiculations in older birds.

As juveniles and immature birds they are chocolate brown in colour and have dark brown eyes making them appear less wicked and evil from their pale-eyed, older counterparts.

There are two different species of Giant Petrels – northerns and southerns.  They are subtly differentiated by a change in their bill tip colour.  The Southern Giant Petrels have a slightly greenish bill tip, whereas the Northern Giant Petrels’ bill tip is more pinkish.  One wonderful aspect of the Southern Giant Petrels is the small population of white morph birds in their species.  These all white birds are neither albinistic or leucistic, they are simply white and in my opinion, they are stunningly beautiful birds to see in the wild.

Many of the Giant Petrels I’ve handled during banding have actually been quite submissive when I’ve held them.  If I’ve ever had an argumentative one, it has tried to spin its head from side to side to make me let go of its bill.  The arguments never last long if you can make them comfortable.  They are often quite nice to handle.

Why Predators and Scavengers are so Important in Antarctica

It’s sad that so many visitors to the Southern Ocean or Antarctica, express disdain at these three bird families when they encounter them but in reality, all three play a vital role in maintaining the health of breeding colonies.

As the cleaners they roam large colonies of breeding penguins and seals in the Sub-Antarctic, feeding off afterbirth, faeces, carcasses and leftovers to effectively tidy the entire place up.  Can you imagine the stench and disease of breeding colonies if none of these birds existed?

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