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Climate change may be turning gulls into cannibals

In this photo taken on July 13, 2016, biologist Jim Hayward shields himself with an umbrella while visiting a large gull nesting colony on Protection Island, a wildlife refuge in the Strait of Juan de Fuca, near Port Townsend, Wash. Hayward’s research has found that climate change is triggering cannibalism among nesting gulls. (Tristan Baurick / Kitsap Sun via Associated Press)
In this photo taken on July 13, 2016, biologist Jim Hayward shields himself with an umbrella while visiting a large gull nesting colony on Protection Island, a wildlife refuge in the Strait of Juan de Fuca, near Port Townsend, Wash. Hayward’s research has found that climate change is triggering cannibalism among nesting gulls. (Tristan Baurick / Kitsap Sun via Associated Press)
By Tristan Baurick Kitsap Sun

PROTECTION ISLAND, Wash. – Jim Hayward slips on a hard hat and pops open an umbrella before stepping into a storm of angry gulls.

Hayward, a seabird biologist based on Protection Island in the Strait of Juan de Fuca, is making his evening rounds through the largest gull nesting colony in the Puget Sound region. He’s been monitoring this site since 1987, so he’s used to the shrieking, the dive-bombing, the frequent splatterings of gull poop, and the pecking at his head, hands and feet.

What he’s not accustomed to is the cannibalism, reported the Kitsap Sun. It’s hard to watch: A fluffy chick straying a few yards from its nest is suddenly snatched up by its neck. Another hungry gull swoops in and bites at the chick’s leg. The mother intervenes but is outnumbered. Her baby disappears under a frenzy of flapping and pecking.

Over the last decade, the gulls have shown a growing taste for their neighbors’ eggs and chicks. The trend appears linked to climate change.

“It doesn’t seem like a lot, but a one-tenth of a degree change in seawater temperature correlates to a 10 percent increase in (the odds of) cannibalism,” said Hayward, a professor at Andrews University in Michigan.

Over the past 60 years, ocean temperatures have increased about 15 times faster than any other time over the past 10,000 years. As temperatures rise, plankton drops into deeper, colder water. Fish that feed on the plankton also drop lower. The surface-feeding gulls, which depend almost entirely on fish while nesting on Protection Island, can’t find enough to eat.

“So they resort to feeding on their neighbors,” Hayward said.

Bird paradise

Protection Island is a high-cliffed and nearly treeless swath of land near the mouth of Discovery Bay about 5 miles west of Port Townsend.

More than 70 percent of the region’s seabirds nest on Protection – a fact that led to its status as a national wildlife refuge in 1982. The 380-acre island is home to the third-largest colony of rhinoceros auklet seabirds in North America and one of the last two breeding sites in the Salish Sea for tufted puffins, which nest in holes burrowed into sandy cliffs.

The island’s ecological value and the fragility of its habitat make it off-limits to the public.

Protection’s only full-time resident is a caretaker employed by the U.S. Department of Fish and Wildlife. Hayward and his wife, mathematician Shandelle Henson, also of Andrews University, spend two months each summer studying the vast glaucous-winged gull population.

High temps, high cannibalism

It was Henson who answered the cannibalism question.

Taking decades of Hayward’s data, she fed it into a computer model loaded with a range of climate and other environmental factors.

“We found that, over the last eight years, there’s a 100 percent correlation between hot years and high cannibalism,” she said.

She also found that gulls are beginning to synchronize egg-laying, possibly in response to cannibalism.

“On one day, we’ll see a ton of eggs. The next day – hardly any,” Hayward said.

Henson’s hypothesis: “If there’s a lot of eggs available all at once, there’s less chance your own eggs will be taken,” she said.

Gulls aren’t picky eaters. They’ll pluck a meal from a dumpster just as readily as a beach at low tide. But during nesting, their range is greatly reduced. They can’t be gone for long from their nests and must rely on whatever the immediate area provides. Increasingly, the region’s marine waters simply aren’t providing.

Forage fish such as herring and sand lance – key food sources for salmon, birds and other marine animals – are in decline. Fish accustomed to warmer water are moving in, but they pack less of a nutritional punch.

“Essentially, they’re getting junk food,” said Scott Pearson, an avian ecologist with the state Department of Fish and Wildlife.

The region’s puffins haven’t resorted to cannibalism, but climate change appears to be making them less committed parents.

During periods of high sea temperatures, Puffins tend to abandon their nests, fail to incubate their eggs or skip the nesting routine altogether. That’s probably because they’re so busy and exhausted from food hunting that they can’t invest time or energy into raising the next generation, Pearson said.

While puffin populations are struggling, a visit to any Puget Sound beach makes clear that gulls are anything but endangered, despite the rise in cannibalism.

But what happens with gulls may be happening or may soon happen with other species that aren’t as easy to study, Henson said. Gulls have long been a favorite species for scientists investigating how environmental changes affect animal behavior.

“They’re big, easy to see and easy to find,” Hayward said. The fact that they nest on the ground in densely packed colonies makes data collection fairly simple. Hayward strolls through each day, counting and measuring eggs and noting the occurrence of chicks or broken eggs in about 300 nests marked with numbered stakes.

“They’re a good indicator species, like canaries in the coal mine,” he said.

Meade Krosby, a research scientist with the University of Washington’s Climate Impacts Group, agrees.

“There’s no doubt climate change has already negatively impacted species around the world,” she said. “We know the oceans are getting warmer, so we can expect more cannibalism.”

Scientists have recently documented climate-related upticks in cannibalism among other species.

As ice recedes in the Arctic, polar bears are finding it harder to hunt seals and other marine mammals. In response, hungry males have been spotted hunting down smaller bears and cubs.

In 2013, warming waters off the coast of Maine sparked a lobster population explosion. With lobsters suddenly the most plentiful food source around, the opportunistic eaters began dining on each other.

“They kind of ate themselves out of business,” Krosby said.

Super cannibals

Cannibalism has been noted in about 1,300 species, including humans. Usually, animals resort to cannibalism as a stopgap measure during periods of food scarcity. Once food is plentiful again, cannibalism ceases.

But what if conditions don’t improve, as appears to be the case with climate change? It could give rise to what Hayward calls “super cannibals.” These are gulls that have largely given up on fish foraging and are instead specializing in hunting their own kind.

“You call tell them because they have scads of egg shells around their territory,” he said. “You see them slowly flap around the colony, and suddenly they drop when they see an unattended nest.”

They also take advantage of the panic caused when an eagle soars overhead. Most gulls begin flying frantic circles, but the super cannibals seize the opportunity, raiding eggs and plucking away chicks.

Cannibal gulls often eat two or three eggs a day – more than enough to meet their caloric needs. Hayward has recorded some of these gulls eating up to 80 eggs in a month.

“For a species, cannibalism is not a good long-term strategy,” Hayward said. “If there’s no food, it can get you across a bad year.”

“But every year,” added Henson, “could be a bad year with climate change.”

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