It is one of the most remarkable wildlife pictures ever taken: in the wilderness of the Antarctic Ocean, three albatrosses glide stiff-winged over the waves just behind the unmistakable dorsal fin of a killer whale.
There are only two black-browed albatrosses in the frame, because the picture is being taken from a miniature camera mounted on the back of the third, a revolutionary development which for the first time has given us the incredible sight of the far corners of the Earth seen through the eyes of an albatross.
Vast stretches of empty ocean, a distant ship, a glowing iceberg, other albatrosses flying alongside; all these haunting images have come from the lipstick-sized cameras attached to the backs of three birds by Japanese and British scientists. But it's the dramatic picture of the albatrosses clearly following the killer whale, or orca, which has aroused the most interest.
It undoubtedly shows some sort of relationship between the birds and the large dolphin which is almost certainly to do with feeding.
The researchers, from the British Antarctic Survey (BAS), Japan's National Institute of Polar Research and Hokkaido University, believe that the images show that seabirds far out at sea sometimes feed alongside marine mammals, perhaps scavenging the scraps that the bigger creatures miss or catching fish which have been forced to the surface.
The research is published online this week in the open-access, peer-reviewed journal PLoS ONE.
"These images are fascinating," said Dr Richard Phillips from BAS. "They show us that albatrosses associate with marine mammals in the same way as tropical seabirds do with tuna. In both cases the prey – usually fish – are directed to the surface and then it's easy hunting for the birds."
The study took place at the breeding colony of black-browed albatrosses at Bird Island in South Georgia, in January 2009, as part of a UK-Japan International Polar Year project.
Four albatrosses were selected at their nest site on Bird Island and still-cameras were taped on to the back feathers of the birds. One camera was not retrieved, but more than 28,000 pictures were taken from cameras on the three albatrosses as they made foraging trips that lasted between half a day and five-and-a-half days to collect food for their chicks.
In each case the camera was combined with depth and external temperature data loggers to study the interactions between the birds and their environment during their long trips. The cameras took one still picture every 30 seconds.
Albatrosses fly many hundreds of miles across the open ocean to find and feed upon their prey. Despite the growing number of studies concerning their foraging behaviour, relatively little is known about how their prey is actually located, which is why the association with the killer whale is so interesting.
Orcas, which are part of the dolphin family, occur regularly over the continental shelf around South Georgia, feeding on prey, such as whales, seals and penguin. The researchers point out that they are also known to feed on Patagonian toothfish by stripping them from longline fisheries.
Black-browed albatrosses feed mainly on squid, fish and krill, but the deep-water toothfish constitutes an important component of their diet in some breeding localities and it appears that deep-water fish could be available to shallow-diving albatrosses only through an interaction with deep-diving predators.
The camera, developed by the National Institute for Polar Research in Tokyo, is removed when the albatross returns to its breeding ground after foraging trips. It weighs 82g, and although it slightly changes the bird's aerodynamics, it did not affect the breeding success of those in the study.