Vultures of the Waves
Although not the prettiest birds to grace the planet, if you ever get the chance to see giant petrels in the wild they will command your respect like few others, says research scientist Jamie Coleman
Sneak a peek at the giant petrels, birds that will command your respect like few others
They may not be pretty but they most definitely are beautiful in their own uncompromising way. There is nothing quite like watching the coming together of hundreds of these majestic giants at a recently deceased corpse. With piranha-like efficiency, they can tear hundreds of kilograms of flesh from an elephant seal carcass in hours, with powerful tube-nosed bills strong enough to crack open a seal skull. Plunging deep into the remains, the heads and necks of these usually exquisitely preened birds quickly become coated with bright red blood and gore. It’s not a sight for the squeamish!
Equally striking is the competition for the optimal place at the feast. The birds posture with wings spread and tails fanned, moving their heads from side to side while emitting their best war songs –
FEW EXPERIENCES ARE AS HAUNTING AS BEING CAST INTO THE SHADOW OF THEIR MAGNIFICENT 2M WINGSPAN.
chillingly primitive guttural cries – to put off challengers. If this deterrent is unsuccessful the birds clash chest to chest, locking bills and slapping wings until one contender concedes. It’s a spectacular display of competitive carnage from this ultimate scavenger.
Yet, in stark contrast to this savage behaviour, these birds are resplendent in flight as they seem to follow ships effortlessly across the Southern Ocean. “Petrels are true masters of the waves with the ability to manoeuvre and thrive in some of the most inhospitable environments of the world,” says ornithologist David Steel. “It’s no coincidence that petrels are most numerous in latitudes with persistent winds. They make flying in the strongest of weather look easy, as wing adaptationslet them exploit the wind’s energy and the air currents that develop over steep ocean waves. This allows them to travel long distances with little waste of energy. These seabirds are true pelagic species and their rather short broad tails and often broad-tipped wings give them the benefits of dynamic flight.”
ADMIRE FROM AFAR
Most human encounters with these prehistoric-looking birds are from a distance and it is easy to underappreciate their true size. Side by side, they would comfortably stand taller than a human adult’s knee height. Few experiences are as haunting as being cast into the shadow of their magnificent 2m wingspan as you walk along a beach with them soaring over your head. The ghostly ‘whoosh’ sounds that accompany their flight only adds to the supernatural atmosphere.
The Antarctic and sub-Antarctic islands where giant petrels breed lack native mammalian predators, so these birds have fulfilled the twin roles of top predator and top scavenger. I am currently living and working on one of these sub-Antarctic islands, South Georgia, roughly 1,390km south-east of the Falklands and 2,150km from South America.
As a product of its isolated nature and extreme conditions, South Georgia has no permanent human residents. Instead, it boasts a conveyor belt of British Antarctic Survey staff, who inhabit the island for a year at a stretch, studying fisheries and Antarctic ecosystems. It is my responsibility to monitor the success of the higher predators on the island, including Antarctic fur seals, wandering albatrosses, gentoo penguins and giant petrels. Throughout the southern summer, I spend most of my time out in the field collecting data on their colonies and monitoring their health. Throughout the winter, when the petrels have departed to their wintering grounds, my focus concentrates on the Antarctic fur seals.
My particular work with giant petrels looks at their reproductive success. I monitor the birds from when the first adults arrive at the colonies until the last chick fledges. I record when birds initiate breeding, how many eggs hatch and when, and the size and weight of the chicks before they fledge. Good feeding by the adults results in fat chicks, which have a higher survival rate than lighter chicks. This sort of study gives a reasonably accurate impression of how healthy the ecosystem is, since any large-scale shifts lower down the food chain will sooner or later affect the keystone predators, whether in a positive or negative way.
We have both species of giant petrel – southern and northern – breeding on the island. As their unimaginative names suggest, each has a geographically distinct breeding range, and they overlap in South Georgia. Northerners arrive in September, just in time for the beginning of the elephant seal breeding season. Their southern cousins appear later, just before the Antarctic fur seals breed and when penguin chicks provide prey and scavenging opportunities. The behaviour of giant petrels differs between each peninsula on the island, depending on the local food resources, since different birds in different areas specialise in different prey. And in seasons where other species fail or struggle, these birds prosper owing to increased scavenging opportunities.
Giant petrels will also feed on the wing, often with skilled precision to scoop morsels and scraps from the surface of the sea, making them particularly susceptible to the accidental ingestion of marine litter. “It’s estimated that as many as 90 per cent of seabirds have man-made items, such as balloons, in their stomachs,” says David Steel.
Both species are largely monogamous. They lay a single egg every year, which is incubated for two months. Chicks are born white-grey and downy, but before they fledge at four months old they moult this down and replace it with darker feathers. As they age, most of them gradually become paler. After hatching, the chick will be guarded by one parent while its mate finds food, but they grow rapidly and within only three to four weeks both adults can head out to forage, leaving the chick to fend for itself – very ably.
From afar the chicks may look vulnerable – but this is by no means the case. Most petrels create
IN THE SOUTHERN HEMISPHERE THOUSANDS OF PETRELS ARE KILLED BY HOOKS ON LONGLINES.
an energy-rich oily substance as a biproduct of digestion, which they are able to store for periods when without food. However, if required, this disgustingly pungent glop can be ejected over large distances to ward off an attack from the likes of a skua. It may not sound like much of a weapon, but the oil binds to feathers and can cause permanent damage. It also binds to clothing and skin, as I know to my cost.
Sadly, smelly glop is no defence against the impact of the fishing industry. In the southern hemisphere many tens of thousands of petrels and albatrosses are needlessly killed by longline fishing fleets. Longlining is a method in which fishing lines with thousands of baited hooks attached are set over the side of a ship into the water column and left to catch targeted prey over a period of time. This practice is associated with the bycatch of many seabirds as well as non-target fish species: the baited hooks make very appetising looking meals for birds, which get hooked and dragged beneath the surface where they drown.
A GLOBAL PROBLEM
The good news is that in South Georgian waters, with the help of the Convention for Conservation of Antarctic Marine Living Resources, alternative fishing methods have been put in place to reduce bycatch. These have been a great success, reducing the incidental death of seabirds from thousands every year in the late 1990s to almost nil currently. Other fisheries are now being encouraged to introduce these simple modifications. Unfortunately, however, many pelagic seabirds have massive ranges and so they simply end up in fishing areas that remain less well-policed and where bycatch is still too high.
Hopefully we’ll find a way to help giant petrels thrive across the Southern Ocean for centuries to come. In the meantime, I feel privileged to get up close and personal with these amazing – if somewhat gruesome – birds. After a day in the field with them I’ve often returned to base bleeding from multiple peck wounds and smelling like nothing on Earth, and several washes later may still be asked to sit at a table on my own for dinner. But it’s worth it.
Southern giant petrel chicks are raised with a spectacular
sea view. After fledging, juveniles spend their first few years on an extensive circumnavigation of the
BELOW: When rearing chicks, the petrels rely heavily on penguin and seal colonies as a source of food
ABOVE: Giant petrels are similar in size to many albatrosses, but have narrower, shorter wings.
FROM TOP: Two giant petrels fight over food; the birds raise their chicks on bare or grassy ground in colonies; feeding on carcasses is a messy business; giant petrels are largely scavengers
RIGHT: There are two colour morphs, white and dark. Young of the dark morph, as here, are sooty black
LEFT: With their meat-cleaver bills, giant petrels have presence