Following last year's massive die-off of Alaskan seabirds, scientists still looking for answers
It’s been over a year now since dead murres washed ashore in the tens of thousands along stretches of Alaskan coastline and other, more unusual areas. This die off was conservatively called “unusually large” at the time in a statement by Alaska Migratory Bird Management (AMBM).
The common murre is a seabird found in subarctic waters, living much of its life out in open water along the North Pacific and North Atlantic. The murre looks like a thin penguin and is considered to be indicator species.
The National Park Service (NPS) says researchers utilize murres as they nest in such large numbers that a change in food availability results in rafts of dead washing ashore. However, the carcasses of an unpredicted number of dead murres were found by marine biologists and regular people alike in 2015 and 2016, sometimes in unpredicted places.
As to how many died, and where, that can be hard to pinpoint, scientists say. Kathy Kuletz, a biologist with US Fish and Wildlife Service, says we still don’t have a definitive answer as to how many, but at least 30,000 dead birds were found. “Geographically and that it lasted a year, that’s unprecedented, Kuletz said. “And we still don’t have a good handle of the numbers of birds, but it’s certainly well over a hundred thousand and it could go many times that.”
Heather Renner, a supervisory wildlife biologist with Alaska Maritime National Wildlife Refuge, agrees. “About 30,000 carcasses were counted in some way or another, but we know only a small percentage of those that die actually make it to the beach. Nobody has generated a useful total estimate, I would say possibly hundreds of thousands were killed.”
And it’s not just how many died, it’s where they died. “There were some in Lake Iliamna, down on the roads along the Kenai Peninsula, and all the way up to Fairbanks. Murres aren’t supposed to be there,” Kuletz said.
In January of 2016, there seemed to be few answers as to what was causing this massive die-off phenomenon, and now, one year later, a definitive answer is still not entirely there. The cause of death is simple enough, according to Renner.
“Almost always it’s been starvation, so it’s clear the birds haven’t been able to find the kind of food that they need. They are relatively large, they have to eat a large percentage of their body mass every day, so they need a lot of food,” Renner said.
But why are the murres starving? Murres primarily eat small forage fish like pollock, a staple in Alaskan commercial fishing. The lack of pollock is where the situation gets murkier.
“It seems very likely that there’s a warm water link to this, but there’s no definitive proof to that. We have observed warm water, and we know that the birds have had a hard time finding food,” Renner said.
Kuletz agrees, saying that the long term trend of ocean waters is a continual warming pattern. “If you look at the long term trend, it continues to warm. And certainly the last couple years have been some of the warmest ever recorded. If you look at the long term, [the die-off] certainly looks related to climate change.”
According to Renner, murres eat pollock when they’re zero to two years old, and commercial fisheries generally harvest larger, older pollock. This could mean that the decrease in murre food source won’t manifest a problem for fisheries for another two years.
“Sea birds are top predators,” Renner said. “They’re sort of sentinels for our environment. They have definitely let us know that there’s change going on in the ocean ecosystem, trying to understand what that change is and how it makes its way back to the top of the food chain is a very complicated process. There are lots of studies going on trying to determine cause of death.”
In addition to the effect that the reduced polluck could have on commercial fishing, the habits of murre and the resulting lack of them could be detrimental to Alaska in several ways, according to Kuletz.
There are still subsistence communities that rely on seabirds for a certain portion of the year’s harvest, both adult birds and eggs. Whale population could also be affected, as the seabirds find fish, and then whales hone in on these feeding flocks.
Kuletz also mentioned that the tourism industry benefits from abundance of sea birds found in Alaska. “The abundance of bird life we have here, people come from all over the world to see them,” Kuletz said.
In 2017, the murre seems to be faring better than last year. Renner says no massive die-offs have been observed this year, however that could be in connection to the exceptionally low birthing season in the summer following the initial die off in 2016.
This reproductive die-off meant a “total failure” of murre reproduction that year, something that could disproportionately affect the ecosystem in the future, scientists say. “The reproductive die off is something we’ve never seen in murres before, widespread. The refuge (AMNWR) has been monitoring these colonies for 4 decades and it’s like nothing we’ve ever observed before,” Renner said.
Renner says there will be similar investigations this summer into the reproduction of the murres that discovered the birth decline in the summer of 2016, to see if the trend will continue. As an indicator species, Kuletz says the murre species could already be adapting.
“Birds like this are pretty adaptable, Kuletz said. "They’ve been here a lot longer than we have, and it’s possible that they would adapt to different prey, so it’s hard to say if the warm water will continue to reduce their numbers. However, we will be watching them closely.”