An Albatross Census From Space
Researchers are using high-resolution satellite images to count the large birds on remote islands.
Peter Fretwell has never been to the remote islands off the coasts of Argentina and New Zealand where albatross make their homes, but he has seen hundreds of them.
Well, he’s seen hundreds of tiny, pixelated white dots against a greenish-brown background on a computer screen. That’s how albatross—white seabirds known for their wingspans—appear in images taken by a high-resolution camera on a satellite orbiting Earth. Fretwell, along with his colleagues at the British Antarctic Survey and the Canterbury Museum in New Zealand, used these images to scour the landscape of distant islands from the comfort of office desks and count albatross one by one to create a census from space.
“It’s a strange way of birdwatching,” Fretwell said.
Fretwell said their recent survey marked the first time that satellites have been used to count individual birds from space. The research, described in a paper in Ibis, targeted two threatened species of albatross: wandering albatross on South Georgia, an island located southeast of Argentina, and northern royal albatross, found on the Chatham Islands to the east of New Zealand’s mainland.
Researchers have gone and studied these birds the old-fashioned away, showing up on boats and wandering through the flora to observe the albatross with their own eyes, or chartering low-flying planes to take aerial photographs. The work can be labor-intensive and expensive. Fretwell described a colleague who spends the Antarctic summers sailing to the islands on a yacht, battling rough seas, and scaling cliffs to catch a glimpse of the birds. Counting albatross from space, Fretwell said, requires much less effort and doesn’t risk disturbing the animals. The Chatham Islands are especially difficult to access, and there were no recent population estimates of northern royal albatross there before the satellite survey, Fretwell said.
Fretwell and the team purchased the imagery from WorldView-3, a commercial U.S. satellite that produces views akin to aerial pictures on Google Maps. Fretwell and the team split up the images into grids, tallying all the pops of white in one grid before moving onto the next because, well, can you imagine losing your place after 300-something albatross? Albatross like nesting on flat, grassy terrain, and their white feathers stand out against the vegetation, making them fairly easy to spot. Here’s what one bird looks like from space:
The team compared their counts to available ground-based tallies and found the numbers were similar, save for one island in the Chatham Islands. The researchers attribute the disparity to a decrease in breeding among the northern royal albatross during the years between the ground-based count and the satellite survey.
Fretwell said the team actually has the U.S. government to thank for this extreme birdwatching. In 2015, federal regulators granted permission to DigitalGlobe, the maker of WorldView-3, to sell images at a higher resolution on the open market, easing a restriction that banned commercial satellite companies from selling images with a pixel resolution sharper than 50 centimeters to anyone besides the U.S. government. The WorldView-3 has a viewing power of 30 centimeters, can see through smoke and spot objects as small as a fire hydrant—or an albatross.
Researchers have used space-based technology to track animals as early as 2004, when scientists from the Wildlife Conservation Society used a satellite orbiting 280 miles above Earth to survey the inhabitants of the Bronx Zoo, snapping blurry photos of giraffes and gazelles. “That’s like standing on top of the Empire State Building and spotting a deer in Maine,” one of the scientists said back then. The resolution has grown sharper in the years since, and researchers have been able to capture animals in far more distant parts of the world than New York City.
In 2011, a group of researchers used satellites to track the population of Weddell seals in Antarctica. Fretwell, who was not involved in the work, said seals are trickier to spot because they appear as “small, black blobs” that could be mistake for shadows on the ice. But the satellite survey matched counts made on the ground, suggesting that the fairly new method could provide accurate data. In 2012, Fretwell and his colleagues used the technology to estimate the populations of two species of penguin on the Antarctic continent, as well as the trail of guano they leave behind, which show up in satellite imagery as brown streaks along the ice. Fretwell has also tracked southern right whales off the coast of Argentina, which show up as white smudges that pop out against deep-blue seawater.
In 2014, a team researchers used satellites to study the distribution of polar bears on a small island in the Canadian Arctic, and another used them to observe wildebeests in the open savannah of a national reserve in Kenya. In 2015, DigitalGlobe worked with a humanitarian group in Africa to capture photos of elephants in the Garamba National Park in the Democratic Republic of Congo, which appear as pale figures that cast distinct, elephant-shaped shadows against beige-colored plains.
Even you, dear reader, can look for animals from space. The researchers behind the Weddell seal project have posted online satellite imagery of hundreds of miles of Antarctic landscape and encourage users to join in their search, tagging teardrop-shaped spots as they scroll through pixels and pixels of ice. That’s the best part about all of this, Fretwell said. Some parts of the study of wildlife populations, a historically arduous and labor-intensive activity, can be done from the comfort of your couch.