This is another diver duck, but is not regarded as a 'fish' duck, in that it may occasionally eat fish/crustaceans, but it primarily eats, like scaup (bluebills), vegetable forage such as coontail and water celery. 

The redhead ducks are about the same size as the greater scaup (bluebill) and is slightly smaller than a canvasback, and/or mallard. For many people, it is difficult to distinguish between a female redhead and a female canvasback, and sometimes even a drake bluebill. The red on the drake redhead's head is a dark red/rust colour, much the same as the rust/red, but a bit deeper than that of common red primer paint often seen on vehicles to be painted. 

Too, a redhead, generally, has a 'puffier' looking head than a canvasback duck, and a broader beak/bill, with more of a blue/grey colour on it. As well, the very front of the redhead beak is rounded, much like a bluebill's, whereas the canvasback beak is a bit slimmer, and goes down to a distinctive hook/down on the top of the beak, at it's tip. The canvasback beak as well, starts much higher up on the duck's head/forehead area. This is where a picture is worth a thousand words, please look at the graphics for a better explanation of what I'm saying here. 

The redhead is a great duck for eating, and decoys readily, and generally aren't as wary as canvasbacks. Because of their similarities in habitat preference, you'll often find bluebills, canvasbacks and redheads all using the same staging areas. Redhead populations were in decline over the past several years, but due to good breeding seasons in the past couple of years, their numbers are rebounding, and here in the Long Point (Lake Erie - Canada) bag limits have risen this year (1997). 

Redheads will decoy to either canvasback or bluebill decoys, and of course, to redhead decoys. I don't know of anyone using primarily redhead decoys in their decoy spreads though, and most hunters will have a few redheads mixed in with their bluebill decoys.