[Tweeters] Common Merganser flock on Saratoga Passage, Puget Sound, March 22

Ray White rw at seanet.com
Wed Mar 25 13:09:20 PDT 2009

Sunday, March 22, about 5:30 pm, I observed a mixed-sex flock of at least 100 (probably not more than 150) Common Mergansers swimming eastward in Saratoga Passage about 200 feet offshore from Whidbey Island's Strawberry Point area. I was on a bluff 75 feet above sea level and too far away to ID the birds by naked eye, but I got clear views through a camera lens equivalent to 10x binocs, and I took photos. Occasionally a male near the rear of the flock appeared to position himself among females and would undertake display behavior, swimming in circles and flipping his tail feathers up. At one point, many males (again in the rear half of the flock or so) reversed course and dashed to the rear and beyond the flock, scooting along with heads low, sometimes shallowly submerged and often with wings violently flapping the water. There may have been some chasing of each other. The whole performance must have been courtship ritual. Is such flocking the usual courtship mode for Common Mergansers? Is it also a migratory aggregation?

Ray White
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