Scaup Staging

Greater Scaup (Aythya marila) scattered on North Basin; then small flock organizing for takeoff.

Scaup stopped here by the thousands in late October (See A Thousand Scaup, Oct. 20) on their way down from their Arctic breeding grounds. On that visit they clustered together wing to wing and beak to tailfeather. Most of them then flew on further south. Now in early March several hundred, maybe a thousand, are here again on their way back north. I was struck by how they scattered. It seemed like they were copying us Covid-struck humans by social distancing on the water. They showed no organizing pattern; their paddlings to and fro looked random, like Brownian motion. But gradually, some patterns started to form. Off in the far distance I saw a circle forming of a couple of dozen birds. Then, closer to shore, as shown at the end of the video above, a fantail of birds formed behind a leader. This was a female closely followed by six other females, with a mixed-gender grouping behind them, gradually tailing off into the random pattern farther back. (See photo below. Males have white sides; female bodies are brown.) The North Basin water is serving as a staging area for the northward migration. They will not all depart at the same time. Small groupings of a few dozen will pull together and take off separately. They will depart in the evening and do their flying at night, like most ducks and many other birds. They’re headed for breeding grounds in the Arctic tundra. They can fly at 75 mph. By the end of March, the North Basin will be empty of Scaup, except probably for a handful who, for reasons known only to themselves, decline to migrate at this time and will stay here into the summer.

As far as I can tell from reading the literature (and I haven’t read it all), we don’t know exactly how small migration groups form out of the random scattering of many hundreds of birds on the water. Are some ducks widely recognized among their peers as migration leaders who know the route and have the stamina to go all the way? If so, how are these qualities communicated? How do individual birds select the small groups they will join? Do the groups have criteria for membership? Lots of questions, no answers. Bird communications can be quite advanced and sophisticated. We humans have a lot of work to do if we’re ever going to understand it.

Flock of Greater Scaup (Aythya marila) preparing for takeoff

More about them: Wikipedia Cornell Audubon In Chavez Park

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