Cassin’s auklet (Ptychoramphus aleuticus) is a small but hardy bird that nests off the west coast from northern California to British Columbia. The birds live in small burrows and eats shrimp and zooplankton, especially krill.

It is normal for some of the birds to die off during the winter, especially during big storms. This year, however, has see a die off of 100 times the normal number of birds. Since October more than 100,000 of the birds have been found from British Columbia to San Luis Obispo, California.

‘‘To be this lengthy and geographically widespread, I think is kind of unprecedented. It’s an interesting and somewhat mysterious event,’’ said Phillip Johnson, executive director of the Oregon Shores Conservation Coalition, to the Salem Statesman Journal.

Although researchers are still investigating the cause, at this point there is no clear reason for the mass deaths. There is no sign of disease and no indication that the deaths are a result of any kind of poisoning. Instead the birds appear to be starving to death, but that raises still more questions.

According to University of Washington biologist Julia Parrish other birds that feed on the same types of shrimp and plankton are not being affected. One possibility is that a ‘baby boom’ among the Auklets has caused increased competition for food and shelter resources.

“We are also hypothesizing — this is not proven, so our best guess — that these birds, which normally can go quite far out to sea — they’re small birds but they’re tough little things, and they’ll spend the winter far out over the North Pacific — we think for some reason the whole population is much closer to the shore,” said Parrish to the CBC.

Dave Nuzum, a wildlife biologist with the Oregon Department of Fish and Wildlife told the the Oregonian that, in addition to the dead birds, wildlife rehabilitation centers have taken in an unusually high number of the birds found alive, but storm stressed. He also stated that he doesn’t expect the die off to let up anytime soon.

“It tends to come in waves. Each time you get a significant weather event, you’re going to get a crush of birds,” said Nuzum.

Additional research and testing is being done in Canada and the United States, including the U.S. Geological Survey’s National Wildlife Health Center in Wisconsin, to try to find more clues as to the cause of the deaths.

At this point there is no real danger to the overall population of the Cassin’s auklet. Although new threats, including oil spills, sea temperature changes and invasive species pose some threat the population is still considered to be healthy. The bird’s conservation status is currently “least concern“.

“It’s a tragic event. It’s an untoward event.… We have never seen a die-off of Cassin’s like this, so that in and of itself says something. I don’t think it’s going to cause the population to wink out, but it’s enough to make me sit up and pay attention,” said Parrish.

Because there is no sign of disease there is no immediate public health concern for people. However, the public is being warned not to approach the bodies and to report any dead birds to local authorities.