Marauding young pelicans have been wreaking havoc on nesting murres at Yaquina Head –clearing the adults from their nests on the rocks and not only eating young chicks but shaking them until they regurgitate fish for the pelicans to eat. In the past two weeks, hundreds of chick carcasses have washed up on nearby beaches after being pushed prematurely from the rocks.
Researchers at Hatfield Marine Science Center studying the murres at Flat Top and Colony rocks say the unprecedented attacks might be the result of a lack of food in the ocean for the pelicans to eat.
According to Associate Professor Robert Suryan, California brown pelican disturbance of murre colonies have been documented on the Oregon coast since 2010, “but none have been this extensive.”
“We observed juvenile pelicans eating chicks, shaking chicks until they regurgitated fish meals and then discarding the chicks to eat the fish, and eating any fish parts that were on the rocks,” Suryan wrote in a report on his surveys.
“The prolonged and widespread disturbances allowed increased access for gulls and corvids, which ate their fill of unattended murre chicks. Finally, in the frenzy of activity related to the pelicans’ movements, untold numbers of murre chicks were pushed from the rocks prematurely. Many drowned or were pummeled by rough surf, while unattended by an adult on the ocean.”
Cheryl Horton has been monitoring the murres that nest on rocks at Yaquina Head as part of her master’s thesis on bald eagles preying on colonies of murres on the Oregon coast. She said pelican attacks on murres are part of the natural order but they are still unusual off the Oregon coast.
“Pelicans were removed from the Endangered Species List in 2009 and eagles in 2007, and they’re really great environmental success stories,” she said. “Everybody’s got to make a living.”
The most unusual part of these attacks was the way the pelicans were shaking the food out of the chicks.
“That was pretty weird,” she said. “We have never seen anything like this before at this site.”
The number of dead chicks washing ashore was completely out of the norm, as well.
It’s become fairly normal for bald eagles to hunt adult murres in their nesting colonies, she said (see the Oregon Field Guide episode on this phenomenon below). After the eagles attack, the gulls and ravens swoop in to eat the unattended chicks and eggs. Eagle attacks on murres have grown to the point where entire colonies on the North Coast have been completely abandoned over the past decade.
Horton said she is looking for ways to document whether the predators are having an impact on the murre population. Common murres have healthy population numbers and spend most of their time at sea. But if they can’t land on the rocks long enough to hatch eggs, said Horton, they won’t produce as many chicks.
Suryan reported around 28 percent of murre pairs in the Yaquina Head murre colony were successfully raising chicks to fledgling age – but that is without accounting for the pelican predation.