Massive Bird Die-off Is Largest Ever Recorded

The murre die-off coincides oddly with the widespread death of other marine animals in the area from whales to sea lions. However, it would seem that these deaths are limited to common murres, rather than thick-billed murres.

The immediate cause of the bird deaths is starvation.

“They just simply aren’t able to find the food that they need to survive,” Renner said. Necropsies conducted by the National Wildlife Health Center in Wisconsin found the dead murres were emaciated, with no food in their gastrointestinal systems and no fat on their bodies.

But what’s behind the starvation?

Renner said biologists are focusing on three potential culprits that may be working independently or in concert with one another. And a common thread is heat, likely related to the “Blob” of warm water that persisted in 2014 and 2015 in the North Pacific and pushed temperatures as much as 3 degrees Celsius (5.4 degrees Fahrenheit) above normal.

“Warm water is implicated,” she said.

Warmer waters might have affected murre food supplies or altered the birds’ food needs by changing their metabolism, she said. Many past die-offs have been associated with warm waters, supporting the argument that the Blob is to blame, she said. The investigation is complicated because biologists have unanswered questions about the winter diet of murres, birds famous for their deep dives to forage for fish in summer.

“We know a lot more about what they eat in the summer than what they eat in the winter,” Renner said.

Another suspect is a series of strong storms that might have scattered already stressed birds this winter, she said.

A third suspect is harmful algal blooms, which proliferate in warm waters and have been connected to some other marine animals’ deaths.

So far toxins associated with algal blooms have not been found in any of the dead murres examined by the National Wildlife Health Center. Though the number of murres dying is very large, biologists are not yet worried about it threatening Alaska’s overall murre population, which is estimated at 2.8 million.

Source: adn.com