The first ever satellite study of the globally vulnerable Spectacled Petrel has revealed new information about the rare bird’s ecology, with important conservation implications.
“For the first time, the species was tracked from its winter feeding grounds all the way to its only breeding site across thousands of miles of ocean,” said Dr. George Wallace, American Bird Conservancy’s Vice President for International Programs. “The data revealed a substantial overlap of Spectacled Petrel feeding grounds with the preferred fishing areas of the Brazilian longlining fleet, indicating that the birds are at high risk from drowning on longline hooks.”
Seabirds often follow fishing vessels looking for a free meal, and can drown when they try to take the bait attached to longline fishing hooks. The Spectacled Petrel has a breeding population of just 9,000 pairs. It was only recognized as a unique species, separate from the White-chinned Petrel, a decade ago, and up until now, very little was known about its non-breeding distribution. However, thanks to a donation of satellite transmitters by North Star North Star Science and Technology, LLC, in partnership with American Bird Conservancy, researchers were able to obtain groundbreaking data on the petrel’s non-breeding activities in Brazil.
Leandro Bugoni and his colleagues from the University of Glasgow, Scotland, and Projeto Albatroz, Brazil, captured five birds off the coast of Brazil using handnets. They attached transmitters to them that provided exact locations every 30 minutes, enabling the researchers to track the birds’ movements, day and night, for about a month.
“The petrels travelled vast distances, each covering up to 45,000 square miles of open ocean. One bird travelled an astounding 8,800 miles in just 49 days,” said Bugoni. Its final journey was from the coast of Brazil all the way to the aptly named Inaccessible Island, the species’ sole breeding grounds in the South Atlantic, mid-way between South America and Africa, at times flying as far as 370 miles in a single day.
To the researchers’ great surprise, rather than foraging in the cold, shallow waters of the productive currents close to shore, the birds mostly fed farther out to sea, in waters nearly two miles deep, and along the continental shelf break.
The Brazilian pelagic longline fleet now sets about 9 million hooks annually. “We know there are high rates of bycatch of both Spectacled and White-chinned Petrels, and also two albatross species, the Atlantic Yellow-nosed and the Black-browed, both of which are considered globally endangered,” said Tatiana Neves, a researcher with the Brazilian conservation group Projeto Albatroz, who has been studying seabird bycatch in the region for over a decade.
Through the satellite tracking project, the Spectacled Petrels were observed travelling similar distances and at similar speeds both day and night, indicating that, unlike the White-chinned Petrels, they may forage around the clock. This is significant for the conservation of the species, because, if verified, it means that mitigation measures must be used at all times of day to prevent bird deaths in the fishery.