Birding: Coordinated Bald Eagle Attack on Mergansers
Birding: Coordinated Bald Eagle Attack on Mergansers
July 27, 2026 — 9:00 AM — Cooper Lake, Washington
We were parked up the road from Cooper Lake in a perfect spot, about 40 yards from the road and among the trees. The night spent there was quiet, and we got up “early” to see if we could spot the American Dipper.
No such luck, so we continued down the lake trail.
I immediately made note of how there were no birds on the water. It seemed odd, but perhaps the lake wasn’t habitable enough in some way.
We continued down the trail along the water, and that’s when we first spotted a female Common Merganser with a single offspring emerging from near the shore.
This made me more aware that something might be off, since Common Mergansers typically have quite a few more offspring in a season. Cornell lists their typical clutch size at 6–17 eggs, and their young are known to face predators including Bald Eagles. (All About Birds)
Again, we continued on, but I couldn’t shake the feeling that something was off about the lake.
Two Bald Eagles
I had found a few Dark-eyed Juncos, Chestnut-backed Chickadees, and Common Ravens when I heard it.
It almost sounds like a gull or a squeaky toy overhead: the call of a Bald Eagle.
I made my way to a clearing to overlook the lake to try to see it.
That’s when I saw them.
Two of them.
Across the lake to the west, perched among the trees but clear as day due to their immense size. Two full-grown adult Bald Eagles overlooking the water.
But the lake was no longer void of life.
There were two Mergansers: one female and one juvenile, wading in the water.
At that point, I started wondering if the presence of the eagles had something to do with why the lake had seemed so barren earlier.
I couldn’t know for sure, but the timing was hard to ignore.
Then, with the distressed call of the mother Merganser, I could only stand by and watch as the encounter unfolded.
The Attack
It was quite impressive seeing the two Bald Eagles swoop down along the water relentlessly as the juvenile Merganser dove, only to resurface as the next eagle came close.
The mother didn’t dive, however. Despite her ability to dive and remain underwater for extended periods, she couldn’t leave her less capable juvenile. Common Mergansers normally dive for less than 30 seconds, although they can remain underwater for up to two minutes. (All About Birds)
Instead, she used what looked like a sort of diving spin attack, propelling her feet into the air. I couldn’t tell whether she was trying to create chaos and disorient the eagles or simply using her strongest appendage to strike at them.
For about 90 seconds, this continued.
Then the two Bald Eagles struck the water within seconds of each other.
The first landed directly on the juvenile as it resurfaced. The second landed only a few feet away.
The first eagle stayed in the water, holding onto the juvenile and preventing it from resurfacing.
The other eagle flew back out of the water and immediately continued its attack on the mother Merganser.
From where I was standing, it looked almost coordinated — as if the second eagle was distracting the mother while the first dealt with the juvenile.
I couldn’t know whether that was actually intentional coordination, or simply two eagles taking advantage of the same opportunity.
It was 21 seconds from the moment the first eagle struck the water until it flew off.
It took a low and direct route to the north, carrying its kill into the trees.
The second eagle perched on a log emerging from the water. It was no longer attacking the female Merganser. The fight appeared to be over.
The Merganser was now wading on the surface of the water, alone.
It didn’t seem to fear the eagle any longer, despite how close it was perched.
The battle was over.
What I Think I Witnessed
We had never seen anything like that.
The entire encounter lasted no more than four minutes.
Sierra was distraught, and I had a similar feeling. We walked back to the bus and discussed what we had just seen.
Looking back, it made more sense why my observations of the empty lake and the single juvenile Merganser had felt off to me. There were large predators overlooking the water, and Bald Eagles are known to prey on waterfowl as well as fish and other animals. (U.S. Fish and Wildlife Service)
But I hadn’t seen anything like the tactics we witnessed that morning, and I never would have guessed that an encounter like this would happen right in front of us.
One thing I still don’t know is whether the two eagles were actually coordinating their attack.
From my perspective, it certainly appeared that way: one remained with the juvenile while the other continued engaging the mother.
I also initially thought the first eagle might have been deliberately drowning the juvenile. But that’s an interpretation of what I saw, not something I can establish from the observation alone. What I do know is that the eagle held the juvenile underwater, remained in the water after the attack, and eventually flew away with its kill.
Bald Eagles are known to dive into the water for fish and waterfowl, and the U.S. Fish & Wildlife Service notes that they may remain in the water or swim with prey when they are too wet to fly immediately. (U.S. Fish and Wildlife Service)
The Common Merganser is also an interesting species to see in an encounter like this. These ducks spend much of their time on the water and are highly capable divers. Their young leave the nest within a day or two of hatching and begin diving for aquatic prey themselves. (All About Birds)
So what I witnessed was a predator attacking a young bird that was already adapted to escaping danger by diving underwater.
I went to Cooper Lake looking for an American Dipper.
Instead, I ended up watching a small and brutal piece of the food chain play out in front of me.
My Birding Video
I made a video showcasing the birds and other things we found during the morning.
I also attached the unedited footage of the Bald Eagle attack below. I wanted to leave the footage unedited so that the encounter could be seen as close as possible to how I experienced it.
What I Observed
Two adult Bald Eagles were perched across Cooper Lake.
A female Common Merganser was accompanied by a single juvenile.
The two eagles repeatedly approached the Mergansers from the air and along the surface of the water.
The juvenile repeatedly dove underwater to avoid the eagles.
The mother remained on the surface and appeared to defend the juvenile.
The mother used what appeared to be a spinning, feet-first maneuver toward the attacking eagles.
After roughly 90 seconds of pursuit, both eagles struck the water within seconds of each other.
One eagle landed directly on the juvenile while it resurfaced.
The second eagle continued engaging the mother.
The first eagle remained in the water with the juvenile for approximately 21 seconds before flying north with its kill.
The second eagle remained nearby on a log while the mother Merganser remained alone on the water.
The entire encounter lasted approximately four minutes.
I don’t know exactly what motivated every movement I saw that morning. That’s part of what made the encounter so fascinating. I can document what I saw, research what is known about these birds, and leave some of the unanswered questions unanswered.
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