Last week while driving past Clearlake in California I got to observe the Crows and Mergansers in action. There were about a hundred Mergansers lined up along the shore and twice as many in a loose raft just offshore. Every five minutes or so a group of about fifteen to thirty Mergansers would start at the shore and swing about a fifty foot arc out away from the shore and then back in again. They would drive the baitfish ahead of them. The crows would line up and wait along the shore. When the Mergansers got close to shore a feeding frenzy would break out. It was fascinating to watch. I tried to get closer to the action but they wouldn't allow an approach of any kind. So the attached photo is no piece of art.
Nice Chris. Not perhaps an example of cooperative feeding, more that the crows are intelligent and opportunistic and have recognised a situation here that they can take advantage of. I assume they were getting the odd fish that swam too far up the beach.
John,
You are correct it wasn't a cooperative act on the part of the crows at all. I didn't observe them helping to guide the fish to the shore or help corral them. They were just making the best of a good thing.
Mergansers and Crows
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