Global warming is turning Washington State gulls into cannibals – ‘Over the last eight years, there’s a 100 percent correlation between hot years and high cannibalism’Posted by Jim at Tuesday, August 02, 2016
By Tristan Baurick
31 July 2016
PROTECTION ISLAND, Washington (Kitsap Sun) – 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. 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. […]
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. […]
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. […]
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." [more]