Common murres show small signs of a comeback from Gulf of Alaska to the Bering Sea
Common murres have had a few bad years. The unusual warm weather temperatures, known as the blob, dramatically shifted the availability of their food supply in the Gulf of Alaska, starving thousands of birds to death. And most murres stopped breeding. But there is some good news. A small amount of baby murres are hatching again in colonies from the Gulf of Alaska to the Bering Sea.
It’s not unusual for common murres to have die-offs. But Heather Renner, a supervisory biologist at the Alaska Maritime National Wildlife Refuge, said the die-off a few years ago was unprecedented.
“There's about two or three million common murres in Alaska and we don't know exactly how many died during the big die-off of 2015 to 2016, but probably about 500,000,” she said.
Renner said it’s clear the warm weather temperatures from 2014 through the beginning of 2017 were responsible for starving thousands of common murres. The sudden change in temperature led to fewer fish for the murres to eat and there are a couple theories as to why:
“One thing that we know is that some bigger fish actually increase their metabolism when water is warm and so they may have a higher need for food themselves,” she said. “So another theory is that maybe there were plenty of the normal number of forage fish available but the bigger fish that were competing with seabirds were actually consuming more themselves.”
The warm water did not just mean dies-offs.
“In the years of the blob there was absolutely zero breeding,” she said. “Very few birds laid eggs at all and the few eggs that were laid failed. They didn’t fledge a chick.”
By fledged, she means successfully left the nest. Renner studies eight different common murre colonies from the Gulf of Alaska to the Bering Sea. Now that water temperatures have returned to a somewhat normal state, she said she’s seeing some changes.
“We are not seeing unusually high numbers of birds washing up on beaches anymore,” she said. “So that's a good thing. There were at least some eggs laid and at some colonies, a couple of chicks fledged as well. So still lower numbers than we're expecting to see in a good year but there was some breeding that took place.”
U.S. Geological Survey Wildlife Biologist Sarah Schoen also sees small but hopeful signs of a comeback. She studies common murres in Chisik Island in Cook Inlet and Gull Island in Kachemak Bay near the Homer Spit. These colonies suffered during the blob. But in Chisik, the birds did make an effort to breed this year, even though no birds successfully left the nest. Gull Island recovered a little faster.
“There were some chicks this year so the birds were doing better,” she said. “It certainly was not anywhere as productive as in the past.”
Schoen is still trying to figure out why and why more birds weren’t coming back to breed.
“It takes a lot of energy to breed, for the females to produce an egg and for the adults to fly to catch fish and provision their chicks, takes a lot of energy so they might have just needed time to kind of rebuild their stores," she said.
Both biologists don't know how many birds from their colonies died during from blob. But Renner said the smaller murre population, by itself, isn’t alarming. Murre numbers were growing in the decades preceding warmer water temperatures and their numbers were able to sustain a few bad years. But their death tells us something is off with what they’re eating.
“We're concerned about what the murres are telling us about the health of the ecosystem but we aren't yet concerned about the health of the population of murres in Alaska,” she said. “The murres sample small fish and large plankton around the waters of Alaska. So the fact that they weren't able to find food over several years indicates that something had changed in the system."
In the past, warm water had only a temporary effect on the birds. If this year is similar to years past, than the birds could take another step toward recovering during this summer’s breeding season. But it’s possible things could be different this time and the murres could take much longer to recover.
Editor's Note: An earlier version of this story incorrectly stated the location of Gull Island. It is in Kachemak Bay near the Homer Spit.