[EBB Sightings] Strange Ducks at Arrowhead/MLK Shoreline on Sun, 1/27/08

Friends: I did not find the Yellow Rail, but I had a good lesson in opening 
mussels from a Glaucous-winged Gull on the boardwalk at Arrowhead Marsh.
There was a pair of "odd ducks": very dark brown, purple, almost black with 
green heads. The larger one had a fluff of feathers jutting out from its 
(his?) head and held the wings at an odd, upraised angle. They both had dark 
bills, dark yellow green with black markings.
They were with mallards in the channel along the path to the boardwalk. 
Exotics? Escapes? They were larger than the mallards they were with. Maybe 
they are resident weirdos that you all know about but they were new to me. 
Any help?
Best of birds to you!
Alan Kaplan