Science

Bering Island Was a Giant, Extinct Seabird’s Last Stand

New fossils show that the Spectacled Cormorant, an enormous bird once native to Japan, had a much wider range than anyone thought.

Spectacled Cormorant. Illustration: John Gerrard Keulemans/The Natural History Museum, London/Science Source

Sometime around the year 1850, the last Spectacled Cormorant died beneath biting seaward winds on Bering Island, a frigid outpost off Russia’s Kamchatka Peninsula.

In the short time the seabird was known to science, it was found only on that one island, and scientists considered the enigmatic bird to be an animal specifically adapted to life there. As a comparatively huge cormorant, with either little will or capability for flight, the bird was thought to echo other quintessential island birds like dodos or Jamaica’s flightless ibises that traded mobility for size on tame, predator-free islands. But 120,000-year-old Japanese fossils described this month in The Auk: Ornithological Advances show that the Bering birds were actually a relict holdout, the last remnants of a formerly wide-ranging species.

The first descriptions of Spectacled Cormorants (Phalacrocorax perspicillatus) were written by German naturalist Georg Steller, who encountered the birds on an expedition in 1741. They were goose-like in size—significantly larger than any other cormorant species—and slow and ungainly, not keen on flying or avoiding humans. These quirks, coupled with the animal’s bulk, abundance, bright yellow eye ring, and double crests atop the head, made the birds hard to miss.

Members of the expedition quickly discovered that they were quite edible. In the decades following, the Spectacled Cormorant fell victim to waves of hungry whalers and fur traders. Only a century after Steller first noted their existence, the island’s giant fish-eating diving bird had disappeared.         

The living birds had disappeared, anyway. In 1960 and 1987, a large set of vertebrate fossils were unearthed in Shiriya, the northeastern point of the island of Honshu. Many of the bird fossils weren’t formally described at the time, which is where many years later Kyoto University researchers Junya Watanabe and Hiroshige Matsuoka came in.

“Once we started to work on the material, it at once became apparent that a cormorant species much larger than any of the four Japanese native cormorant species was represented in the fossils,” says Watanabe, lead author on the new paper.

The team initially thought that they might have a new species on their hands. But when Watanabe looked closer at the 13 fossil bones, he found that the dimensions were incredibly similar to Bering Island’s giant cormorants.

“Eventually,” Watanabe says, “we became quite convinced that our Japanese fossils belong to the same species as the bones collected on Bering Island.”

The Spectacled Cormorant, then, likely resided in prehistoric Japan some 1,500 miles south of Bering Island—giving the species a much larger range than anyone thought. That would also mean that whalers and fur traders alone didn’t drive the species extinct. Watanabe doesn’t think prehistoric peoples put hunting pressure on the birds, though, since the birds’ bones aren’t found in archaeological kitchen trash heaps, better known as middens.

Instead, Watanabe ties the cormorants’ extinction to a prehistoric climatic shift that began long before the relict population on Bering Island was extirpated. Paleoclimate data show that some 20,000 years ago, plankton living in the sea surrounding Shiriya experienced a population drop. The loss of an important food source like this would have likely disrupted local food webs and affected seabird populations, potentially causing die-offs not unlike recent mass deaths of Tufted Puffins in the very same sea. Events like this could have narrowed the cormorants’ range from a ribbon of territory stretching along the edge of northeastern Pacific—from Kamchatka, through the Kuril Islands, and into Japan—to Bering Island alone, where the remaining survivors were quickly picked off.

It also means that the story of the Spectacled Cormorant’s extinction is more complex than those we tell about more famous giant island birds like moas and dodos, which appear to have perished primarily by hunting.

Jamie Wood, a paleoecologist with Landcare Research (Manaaki Whenua in Māori), one of New Zealand’s Crown Research Institutes, who was not involved in this study, notes one extinct lineage that may be similar is that of Australia’s emus.

“At the end of the last glacial period, rising sea levels cut off [the] island population of emu, which then became quite different to mainland populations,” Wood says. “But [they] were hunted to extinction by humans.” This process occurred multiple times to different emu populations on different offshore islands.

The study helps illustrate that the species distributions we see today sometimes only capture a small slice of a species’ lifespan—which can stretch back hundreds of millennia. For example, up until the late 1800s, grizzly bears were found over much of the North American continent, even in plains and deserts. Lions prowled southern Europe as recently as 2,000 years ago.

The Steller’s sea cow (Hydrodamalis gigas) lived throughout the North Pacific in prehistoric times, but by the time of its discovery, it was limited to the seas surrounding Bering Island—which it shared with the cormorants. And like the cormorants, the large dugongs were also hunted to extinction by Steller’s expedition mates and subsequent whalers and fur traders visiting the island.

The shared range collapse to the island may not be a coincidence. Watanabe and his colleagues are now studying other extinct seabirds from the region to further investigate the climate-change hypothesis that might explain the fate of Bering Island’s most incredible, and mostly forgotten, seabird.

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