While the onset of winter marks the
departure of most of Bird Island's wildlife, there's one iconic
resident who stays with us through the cold, dark months.
The Wandering Albatross, Diomedea
exulans, are truly amazing birds. They look unreal sometimes,
like a huge relic of a prehistoric age as the adults stand well over
a meter tall and can weigh more than 10kg. Their wingspan is the
largest of any living bird, at up to 3.5 meters. That means they can
soar above the oceans for hours at a time without expending any
energy flapping, searching for food in the vastness beneath.
They mainly eat cephalopods but will
readily take crustaceans, small fish and carrion. We regularly find
regurgitated piles of squid beaks beside their nests which can be
collected for measuring and identification to enhance our
understanding of their diet – small changes may be indicative of
greater changes to the marine ecosystem.
Wandering albatross are frequently seen
from ships in the Southern Ocean. Described as a 'bird of good omen'
by Coleridge, they can follow them for days, often feeding off any
scraps thrown overboard. Unfortunately this has been hugely
detrimental to their health as they can get caught, tangled up and
drowned by the long-line fisheries boats. Advances are being made
with deterrents and legislation about operating procedure,
particularly around South Georgia where by-catch has been hugely
reduced, but it continues to be a problem in less well regulated
parts of the ocean.
|Copulating pair, an infrequent October sight.|
They build a nest out of mud, moss and
tussack grass that will be used year after year and stands around
40cm high. These are spread in loose colonies across the island. In
mid to late December a single egg, white and 10cm long is laid and
incubated by both parents.
|Chick on the nest with both parents present.|
Between Christmas and New Year the
albatross assistants, with as much help as is available, cover the
whole island counting and marking each nest with a numbered stake and
GPS plot point so we can map them. Where possible we'll record ring
numbers of both birds – this often means repeated return visits as
each one can be away from the nest for well over a week. There is a
ridge behind the base where the birds are studied more intensively;
they carry coloured darvic rings so they can be identified with
minimum disturbance and at times the area is visited daily to get
precise laying and hatching dates.
|Checking for eggs. The clipboard is useful not only for making notes but also as a bit of protection. The birds are not particularly aggressive but those beaks are big and sharp.|
With this simple long-term monitoring
we can build up a life history of the population, looking at changing
trends in survival rates, life expectancy and breeding success. With
such long-lived birds, over 50 years, it's important to have
consistent monitoring techniques so we can draw comparisons over time
and with other locations.
While the established pairs are
alternating time between egg-sitting and fishing the younger,
unpaired birds are searching for partners. Wanderers are monogamous
and generally mate for life but there's always single birds trying to
impress others. They gather in groups and show off by spreading their
wings, throwing their heads back and uttering a variety of gurgles,
screams, whistles, grunts and snapping. Later on they may tap their
bills together and mutually preen each other. These rituals are
repeated by long-term pairs re-establishing their bonds.
|Young male (front) spreading his wings and skycalling to impress the female on the right. Behind him another copies his obviously impressive chat-up techniques.|
|A long-term pair preening each other to re-affirm their partnership.|
Incubation takes the best part of three
months. Once the egg hatches the adults continue taking turns looking
after the chick for another few weeks. By the time it's old enough to
be left alone, early April, they've got a deep layer of downy
feathers over an inch thick and the ability to vomit oily,
plumage-ruining sick on anyone they perceive to be a danger. Despite
this defence many Wanderer nest sites have been decimated by
introduced land predators such as cats, rats and mice. One of the
reasons Bird Island is so important is that it has never hosted these
predators and it is hoped that the rat eradication on the South
Georgia mainland will re-open historic breeding grounds.
|Young chick being preened and cared for by a parent.|
|Poking a head out from under a leg for a view of the outside world.|
As the winter approaches and the island
gets covered with snow and ice the chicks sit tight on their nests,
islands of warmth amongst the inhospitable cold. During the harshest
storms they sit tight, curled up asleep with their heads tucked down.
During this time they are visited roughly once a week by each parent,
returning with a belly full of rich food that they regurgitate
straight into the hungry chicks.
|When snow covers the island all that stands out are these small balls of warmth.|
|Young chick getting a delicious, oily snack.|
Throughout the season the nests are
visited at the start of every month to check which ones have hatched,
how the chicks are progressing and to record any failures. In late
August, with the chicks still mostly fluffy but with dark adult
feathers showing through, we go out and fit them all with unique
identification rings. Before coming south the largest bird I'd ringed
was a Greater Black-backed Gull. At the time that seemed pretty big,
especially compared to the Willow Warblers and Chiffchaffs I was used
to, but although the techniques are pretty similar there's some major
differences in how to hold these birds.
Data retrieved from birds with rings, and more recently those carrying tiny geolocators, was told us all sort of information about their range, routes and feeding areas. It helps to know these things when trying to protect them and their key habitats.
|Engaging in some friendly chat with a healthy looking chick.|
|An unconventional approach to ringing. This strange position keeps the chicks passive and safe, allowing a quick squeeze to apply a unique ring.|
Around November, after about nine
months on the nest, with the weather warming a little in the
Antarctic spring the chicks start to fledge. By this time they've
lost their down and have a complete covering of dark adult feathers.
For a long time they get off the nests and walk around, investigating
their surroundings. On windy days they'll hold out their wings,
feeling the breeze rushing through their feathers and trying a bit of
flapping, building up those flight muscles. This increases the older
they get and late in the season you can see these huge birds facing
into the strong winds, jumping and flapping, getting 6ft in the air
but wobbling in a rather uncontrolled manner as they try to master
the balance and timing it takes to move in a straight line. It takes
a lot of practice to make flight as easy as the adults manage.
|An almost fully developed chick getting a visit from both parents. It's rare to see both adults together, particularly at this stage in the season when they are both continually heading out and returning with food.|
|Letting the breeze blow through your wings must be a great feeling. |
|Not far off departure, looking for a launch spot.|
Once they fledge the young will
probably spend at least the next five years at sea before returning
to their breeding sites, though they don't usually start mating and
laying eggs until they are 10 - 15 years old. During this 'teenage'
period they will follow the circumpolar winds and currents,
travelling clockwise around the whole Antarctic continent. A
successful pair will not breed for another year and instead will
return to the ocean where they are most at home, soaring effortlessly
over the waves on huge, unflapping wings.