The comeback of the bald eagle is one of the most celebrated success stories of modern conservation. But along the Pacific Northwest coast, the majestic eagles are marauders. Their increasing numbers are putting other bird populations at risk. For now, biologists are not inclined to intervene. The eagles’ prey must adapt or die.
Most every day of the week, you can find birdwatchers Bus and Delena Engsberg at an observation platform by the Cape Meares lighthouse on the northern Oregon Coast. For years, the couple has aimed high power spotting scopes at the nearby cliffs and offshore rocks that teemed with seabirds.
Delena Engsberg: “When I aimed this out here, we would have fun with the children. We’d ask them to count the birds. One time, a little boy said, ‘One, two, three… LOTS,’ because there were thousands… Now, as you can see, there’s not a thing there.”
Delena Engsberg and her husband have watched as bald eagles in the last few years have driven the huge colony of common murres off their nests.
The common murre is a black-and-white diving bird that resembles a small penguin. The Engsbergs have captured dramatic home video of eagles flushing the seabirds off the rock. Then the real damage happens.
Crows and gulls swoop in to gobble up unguarded eggs.
Video: “Aha! Oh, great. This eagle just went and grabbed a murre. You can see it carrying it in its talons…”
Home video by Delena & Bus Engsberg
The Engsbergs say murres have abandoned the nearby Three Arch Rocks as well. That used to be the biggest common murre colony south of Alaska.
Bus Engsberg: “It’s not only the murres that are affected. It is the cormorants, the gulls, everything. This is a real disaster.”
This is the first year Bus Engsberg has seen hungry eagles drive cormorants off their nests and eat their eggs.
Biologist Roy Lowe oversees the National Wildlife Refuges along the Oregon Coast. From his post in Newport, he’s watched the murres beat a retreat as bald eagles expand their range from north to south.
Roy Lowe: “Now, every colony north of Yaquina Head is either not productive or is producing very, very few young. So we’ve basically lost all of the breeding colonies north of here. Birds are still returning. They’re coming onto the colony, they’re laying eggs, but the disturbance is so repeated that they are being flushed off the rocks.”
Common murres are not endangered now, but Lowe expects to see the seabird population decline given the cascade of nesting failures.
It’s an environmental paradox. The recovery of our national symbol threatens another species.
Roy Lowe: “The predator-prey association isn’t always easy to watch, you know.”
At least one park manager wonders out loud whether to haze the resurgent eagles during murre breeding season. But Roy Lowe says that’s just not going to happen.
Roy Lowe: “This is a natural situation. So we’re just trying understand it, document it as well as we can and see how it unfolds.”
Some bird researchers are seeing signs of adaptation.
Oregon State University biologist Rob Suryan monitors a seabird stronghold from a perch high atop the Yaquina Head lighthouse. He gets a fantastic overhead view — and an earful — from the murre colony on the rocks below.
These barren rocks still teem with tens of thousands of murres packed shoulder to shoulder tending baby chicks. Suryan says this colony has tripled in size in recent years.
Rob Suryan: “For one, these birds are finding safety in numbers. But also, part of the story is the eagles, their presence on coast — especially on the north coast where there are more eagles — seem to be redistributing the murres.”
Off the northwest tip of Washington state, University of Washington scientist Julia Parrish has observed adjustments occurring at Tatoosh Island.
There, some murres are nesting under bushes to hide from eagles. Cormorants are adjusting too.
U.S. Fish and Wildlife Service biologists are seeing more of them nesting under bridges along the coast. It may be a way to stay safe from eagles.