Climate Change Might Have Some Gulls Resorting to Cannibalism

With rising sea temperatures making food scarce, Puget Sound's Glaucous-winged Gulls have turned to their own species for nourishment.

On Protection Island, gulls like their eggs raw or hatched. Here in the largest nesting gull colony in Puget Sound, cannibalism is on the rise—an eerie and unprecedented phenomenon that scientists have linked to climate change. Analyzing a decade of data from the island’s population of Glaucous-winged Gulls, researchers from Andrews University found a high correlation between hot years and egg cannibalism. 

"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," biologist Jim Hayward told the Kitsap Sun.

According to Hayward, when the water warms, it creates a domino effect in the food chain that leaves the gulls without their most reliable food source. From the Sun: 

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.

Observed in roughly 1,300 species, cannibalism is a common coping mechanism for times of food scarcity. It’s already happening in polar bears and lobsters affected by melting ice and warming seas. But cannibalism isn’t just unsavory; it’s evolutionarily unsustainable. And while most gulls are far from endangered, this climate-caused behavior may soon exist in threatened bird species. 

More than 70 percent of Puget Sound’s seabirds nest on Protection’s 380 acres, including the third-largest colony of Rhinoceros Auklets and one of the Salish Sea’s last colonies of Tufted Puffins. While the gulls are the only species yet to resort to egg cannibalism, the researchers have noticed that rising sea temperatures are leading many puffins to abandon their nests, too exhausted by food hunting to incubate their eggs.

Some good news for the birds is that the National Oceanic and Atmospheric Administration
issued a ruling this spring protecting vital fish species off the Pacific Coast—a monumental victory for seabirds and their prey—but that will only help so much as long as warmer water temperatures persist. And so, at least for now, baby gulls on Protection Island will have to stay extra alert in this new bird-eat-bird world.