Pied-billed Grebe.... what was that?

Kinda of an uneventful day birding.... Took a run over to Stoney Creek Metropark... Didn't see much on the lake... A bunch of coots and a big flock of Canada Geese at Eastwood beach.... Some smaller geese, but I didn't feel comfortable calling any of them Cackling Goose.... While scoping the Geese, a pair of Pied-billed Grebes came close to shore and each one started flapping there wings rapidly... one at a time... then they swam away... Not sure what that was about but it was interesting to watch..... Feeders in my yard were going crazy today... Mostly Goldfinches, House Finches and Juncos.... Saw a few Tree Sparrows, but none ventured into the feeders...

Pied-billed Grebes