Tweeters,
Today, March 3, I watched a harbor seal chase, mortally injure, and at least partially devour an adult Common Merganser. This occurred on the Duwamish River next to the Boeing Developmental Center (off East Marginal Way across from the Museum of Flight) between 2:17pm and 2:39pm.

I'd been scanning the river and saw two male Common Mergansers with one female near a flock of Mew Gulls. As I scanned to the right, I saw what I thought to be two more mergansers, one of which was chasing the other. (The glare off the river at that particular time made it difficult to see, but the one being pursued was clearly a Common Merganser.) When "one" of the mergansers surfaced, a harbor seal head popped up right next to it. The seal went under the merganser, and (apparently) pulled the merganser under. The merganser went under backward, which is not the usual way it dives. I realized then that what I mistook for the second merganser was the head of the seal as it pursued the merganser.

In the next several minutes, the merganser would occasionally float to the surface--head up--and the seal would surface either next to it or very close by. The seal would then push the merganser and then dive beneath it, or simply dive beneath it. In either case, the merganser would go under, either straight down, tipped forward, or tipped backward. This occurred at least 7 times during the succeeding minutes. Once, the merganser came to the surface in a "flattened," head-down-on-the-surface position. Once, I saw the seal grab one of the orange feet of the merganser and pull the merganser under the surface. At no point after the initial chase and submergence did I see the merganser open its wings or otherwise attempt to escape.

The last time I saw the merganser apparently alive (it turned its head to the side), the seal pushed it, then submerged, whereupon the merganser was again pulled under. A minute or so thereafter, the seal surfaced with something in its mouth (not a fish: very white) and then dove. Several minutes later, I relocated the seal when it surfaced. I did not see the merganser again. I did see some feathers on the surface, but that may have been from the initial chase.

At 2:45 pm, I saw the seal moving against the tide back down the channel.

I've certainly heard of sea mammals attacking and eating birds, but this was the first time I'd personally seen it.

Denis J. DeSilvis
Phantom Works - The Boeing Company
206-655-1938
denis.j.desilvis at boeing.com