Giant Petrels

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.

Geep scrap. These two males were fighting over a nest. The female sat by passively and then left with the loser. Like with most animals the fights are mainly posturing, establishing who is bigger, but then can lead to the interlocking of beaks and with those very sharp tips it's not unlikely that some blood will be spilt. This usually seems to signal the end of the fight.

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.