Snow Petrels
Pagadroma nivea

1/ What are snow petrels like?

4/ Isn't it cold and windy sitting out on the sea ice?

In their appearance and behaviour, they symbolize the very essence of the deep south. They are frequently encountered in hundreds, rarely in thousands, but tend to be spread out over a wide nesting area rather than arranged into large colonies as are other Antarctic species.

They feed largely on krill and must always be near to the sea in order to feed. They are found therefore particularly along coasts and along the Antarctic peninsula.

The courtship ritual consists initially of a male snow petrel following a female as she flies around the nesting area which is frequently a rocky outcrop or cliff with suitable ledges or nest holes. 

The female then leads him around the cliffs in a high speed aerial ballet, climbing and diving, flying almost into the cliff face at full speed before changing direction with an imperceptible twist of the wing. The poor beleaguered male not only has to match this aeronautical master class, but he has to do it as close as possible to the female and without a script. Many seem to give up and get left behind, certainly in the early days. In this picture the male is calling to the female during a relatively relaxed moment.

Photographing this requires a lens on fixed focus, bright light, fast shutter, small aperture, a pile of film and much cursing. Even then, it all happens so quickly that you don't really know what you've got until the film is developed.

Attempting to approach a nest (as I did on many occasions when helping in a long term programme on nesting success) brings out the worst in snow petrels. A well aimed stream of foul smelling, bright pink, oily, semi-digested krill mixed with oily stomach secretions would come in your direction as their (admirably unpleasant) defence mechanism.

Snow petrels have been known to nest far inland on the Antarctic continent, nearly 200km. from the nearest sea that they must travel to in order to feed. They must nest on rock and in these cases choose "nunataks" isolated outcrops of tall rock ridges and mountains that protrude above the surrounding ice from the bed rock.

They frequently arrive surprisingly far south in the winter in ridiculously low temperatures and high winds for such small creatures and rest overnight on totally exposed sea-ice, as here. Any spring and summer shelter is blocked up by now. The reason they venture south in such adverse conditions would seem to be in order to take advantage of the abundance beneath the ice and the relative rarity of summer competitors.

That these animals are prepared to undergo so much to find their food is testament to the nutritional value of that food - krill. Here snow petrels (and in the first photograph a crabeater seal too) are taking advantage of a tide crack to fish through in the case of the birds and to breathe at in the case of the seal. A tide crack is a long narrow open lead of water that stretches between two points such as nearby islands or exposed rocks. It arises when the tide rises and falls, when the tide rises the crack opens when it falls, the crack closes. Such tide cracks can easily stretch for several kilometres, but never being more than about 50cm wide. 

The snow petrels space themselves out along the tide crack and sit patiently waiting for a krill to swim by at which point they jump out and hover just above the surface to take the tasty morsel.