Last week, Bufflehead ruled the North Basin Cove; they were everywhere, in loose rafts, in small groups, and solo. This week the Scaup have taken over. Long trains arrived and at the time I visited there were three rafts of them, each well over a hundred birds strong.
As a beginning birder, I could well be mistaken when I identify these as mostly Greater Scaup. The Lesser Scaup are also here. The Greater have heads that are more rounded and less peaked, and shorter, rounder foreheads, than the Lesser. These in the video look like Greater to me. Expert birders out there, feel free to post dissent; it wouldn’t be the first time I’ve made a bird ID mistake.
What was most curious to me about these birds was how they decided which way to paddle. In the video above, you’ll see a sequence where individual birds suddenly do a 180 and paddle the other way. The whole flock around them did that. Which bird initiated that change, and why, and how that got transmitted to the flock, was not obvious at all. Each of the rafts that I observed were actively paddling, sometimes diving, in Big Picture patterns without obvious plan or purpose.
I’ve seen studies of how motion changes happen in schools of fish and in dense flocks of flying birds. If anyone has information about the motions of rafts of swimming birds, please post.