The giant petrels, commonly known as 'geeps', are one of my key study species.
They're split into two species – the Northern and Southern,
differentiated by the colour of their bill tip. Red for Northern and
green for Southern. The sexes are basically the same, with the males
being marginally bulkier and with longer beaks.
Northern Giant Petrel. Check out that lovely eye and the impressive beak - the salt gland on top to enable filtration of sea water and the huge pointed tip for ripping through carcasses. |
The geeps get a
bit of a raw deal. The only time you'll see them in any sort of
nature documentary is when they're scavenging dead seals or waiting
patiently for defenceless young pups and penguins. They'll be
fighting with each other for rights to the kill, then shoving their
heads right inside these big dead seals, pulling out covered in
blood.
No waste on Bird Island. A recently deceased Fur Seal will quickly be reduced to a pile of bones and the geeps are the first ones in there. |
They're not as
eye-catching as the penguins or as elegant as the albatrosses, but
once you start spending some time with them you get captivated by
their charisma.
Describing
them
is
a
bit
like
describing
a
Frankingstein.
They're
the
largest
of
the
procelleria
family
of
petrels
and
prions.
Normally
when
you
think
of
these
birds
you'd
think
of
petite
Storm
Petrels
or
the
elegant
shearwaters
soaring
over
the
waves,
perfectly
adapted
for
a
life
at
sea
but
a
little
ungainly
on
land.
Unlike
the
smaller
members
of
the
family
the
geeps
have
strong
legs
that
enable
them
to
stalk
the
beach
like
dinosaurs.
When
they
fight
over
food
their
tails
are
up,
like
turkeys,
and
their
wings
outstretched
as
they
run
at
each
other,
shrieking
like
banshees.
A beach-master pose as this geep challenges anyone else to try taking his food away from him. |
Like most
wildlife, it's when you see them with their partners and young that
you really warm to them. Giant Petrels are monogamous with long-term
pair bonds and often nest in the same place, frequently the same area
they were born, year after year. Many of them hang around, with their
partners, through the winter.
A pair circling and calling together. |
They're amongst
the earliest nesters on Bird Island as the Northerns start laying
eggs in mid-September with the Southerns about a month later. The
nest can be a simple scrape on the ground but is usually a turret
built from mud, moss and tussac grass. An ambitious pair may try to
use an old Wandering Albatross nest.
The pair will
take turns sitting on the egg for around a week at a time while their
partner is off feeding. The egg takes about two months to incubate
and during this time the birds have to put up with whatever the
weather throws at them – wind, rain and snow. There's no
ground-based predators here, no rats or cats or mice (which is one of
the reasons Bird Island is so important), so there's little threat to
the geeps from other life. With a bill like that they're not worth
messing with, although there's the occasional territorial squabble
between adults.
Each of the
approximately 500 nests in my study area gets a number and I'll take
a GPS reference so I can plot them on a map later. The majority of
the birds here carry rings and darvics. I'll take the numbers down
and enter them onto an existing database, from that we'll know
whether each individual has stuck with the same partner, changed
location, been seen before and many other things. Throughout the
season I'll visit about once a week to check on the progress of the
egg and chick, ultimately recording whether the pair have bred
successfully or not.
Writing down nest number, location and ring numbers of a particularly unconcerned pair. (Hannah's photo). |
This is all part
of an ongoing, long-term study collecting data on these species to
find out all sorts of things like population and population changes,
breeding success and survival rates.
Giant Petrels are scavengers as well as predators and can often be seen following boats in the south seas, waiting for any scraps. |
Amongst the
Southern geep population there's the occasional all-white individual.
It's not an albino, it's just a morphological difference. They
interbreed with the more usual coloured birds. There's two females
like this in my study population of approximately 300 Southern Giant
Petrels.
A white morph chick, pretty much full grown and ready for departure. |
Two months after
being laid a little white chick pokes its way out the egg with this
big clunking beak. It's parents stay with it, continuing their
regular change-overs for another few weeks, after which time it is
left alone. Like most birds of it's kind it defends itself with a
snapping bill and the threat of regurgitation – viscous vomit that
could ruin an assailant's plumage, fur or jacket.
A week-old geep chick getting it's first rays of sunshine, yawning or calling for food. |
As they get
older the young birds lose their downy fluff and grow a layer of
sleek, black adult feathers. They start to wander away from the nest,
but not too far as you never know when a parent will return with
food.
Half way through chick development, when they've grown to a decent size but are still covered with down, keeping them warm as the adult feathers develop beneath. |
By March the
Northern chicks are three to four months old. I'll head round the
study area and take weight and bill-length measurements from all of
them, also giving them a unique ring so they can be identified in the
future. All that remains then is for them to lose their remaining
chick feathers, stretch out their wings and head off to sea. By
mid-April they'll all be gone with the Southern geeps about a month
behind them.
Ready to go. This was the first egg laid last season, in mid-September. By mid-March she was looking beautifully slick and smart and was soon to depart. |
They're
long-lived birds. I've not seen any figures for ages but there's ones
here breeding that are older than me and it wouldn't surprise me if
they can get to double that age. Many of these chicks will return to
the same areas of their birth to breed, but it'll be a few years
before that happens. I was finding apparent first-time breeders this
season that were ringed here as chicks in 2005 and 2006. Ongoing
experiments using tiny geolocator devices are trying to work out
where the young birds go during their teenage years. Ringing
recoveries have shown that within a few months of leaving these young
birds can be found as far away as Australia. Similar such work has
shown a difference in feeding strategies, with females more likely to
feed out at sea while males patrol the beaches. As with all good
science, the answers are sure to throw up many more questions.
Southern Giant Petrel. Their presence on the island during the winter is one of the highlights of going for a walk. |