Two male Common Goldeneyes (Bucephala clangula) at the north end of Bodega Harbor this afternoon (near Porto Bodega) — the adult has a glossy green head, while the younger male has a chestnut brown head (note the beginnings of the white loral patch between the eye and the bill in the following photos).
Over and over again, these birds would lower their bills to the surface of the water and then tilt their heads back. See photo above and next image, too. Do you have a guess about what this behavior is about?
Goldeneyes have a dramatic courtship display, but in that case they arch their heads all the way back to their rumps, and the entire display involves even more ritualized movements. I didn't mention it, but we didn't see any females nearby today.
So we think this was drinking behavior — scooping up water from the surface and then using gravity to let it run down their throats. I mentioned that this was near Porto Bodega, so perhaps there was fresh water at the surface where Johnson Creek runs into the harbor.
It would be interesting to keep an eye out for this behavior to see if it occurs more frequently near creek outflows or other sources of fresh water.