Jeanna Bryner, livescience.com Yahoo News 7 Oct 09;
Miniature digital cameras have caught for the first time an albatross feeding alongside a killer whale, waiting for scraps from the messy eater, scientists report.
The snapshots spotlight the so-called black-browed albatross (Thalassarche melanophrys), a seabird named for its dark eyestripe, with a wingspan of just under 8 feet (2.4 meters) and weighing up to about 10 pounds (4.5 kg). The birds are declining about 2 percent to 4 percent every year, partly as a result of getting caught on long fishing lines.
Though past research has provided insights into what albatross eat, relatively little is known about how the seabirds spot fish prey in the seemingly "featureless" open ocean. The new study, detailed this week in the journal PLoS ONE, suggests they do so in groups when diving and might even rely on a top predator to bring hard-to-reach fish food to the surface.
One caveat: Many of the images were too dark, obscured by feathers on the birds' backs or, as in most cases, just of the open ocean rather than a foraging event.
"Out of the many, many thousands of images we got, there were remarkably few that showed us how they feed. It is a big ocean," study researcher Philip Trathan of the British Antarctic Survey told LiveScience. "We have a lot of pictures of this very big ocean." He added that technological advances could allow for smaller and lighter cameras that can be fitted onto the birds' heads (to ensure feather-free scenes) as well as cameras with video capability.
Cameras onboard
In January, the research team attached miniature digital cameras, each about the size of a large lipstick and weighing about 3 ounces (82 grams), to the backs of four black-browed albatross breeding at colonies on Bird Island, South Georgia, in the Southern Ocean.
Over about five days, the cameras collected some 28,725 images, revealing the birds dive relatively infrequently, though when they do take the plunge they tend to do so with other birds, and in one case with a killer whale (Orcinus orca).
The killer whale snapshot revealed a camera-equipped albatross along with three of its kin following the top predator. Subsequent images, however, got obscured by the albatross's feathers, though temperature measurements suggest the albatross did land on the ocean surface after spotting the killer whale.
Ocean pals
Here's what the albatross get out of the deal: Killer whales feed on a wide range of prey, including other whales, penguins and Patagonian toothfish (Dissostichus eleginoides) by stripping them from longline fisheries. While black-browed albatross feed mainly on squid, fish and krill, the deepwater toothfish can be an important part of their diet in some breeding grounds, the researchers say.
Since albatross are shallow divers, they can only access the toothfish through an interaction with deep-diving predators like killer whales, or with commercial fisheries, the researchers say.
And the albatross depend on messy eating of sorts. When killer whales feed, fragments of their prey are often left near the sea surface, where clever seabirds can snatch them without expending too much energy.
"Targeting the less-mobile prey fragments may also reduce the number of plunge dives needed to capture a prey item," the researchers write. "Therefore, a close association with foraging killer whales would help albatrosses to find food more efficiently in the apparently 'featureless' sea, especially in a year when the availability of aggregative prey species (such as Antarctic krill in South Georgia) is low."
What do killer whales get out of the deal?
"On very rare occasions, I suppose if an albatross stayed on the surface within reach of the whale for too long, there is a remote chance it could itself be eaten," Richard Phillips, also of the British Antarctic Survey told LiveScience. "Many tropical seabirds are eaten by sharks, and indeed this is one explanation why most tropical seabirds do not roost on the water overnight but instead return to land." Phillips leads some of the Survey's albatross research, but wasn't directly involved in the current study.
Revealed: the albatross's unlikely dinner date
Images from camera mounted on bird's back show giants of the skies hunting for food in concert with killer whales
Michael McCarthy The Independent 7 Oct 09;
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.
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