Like any amateur chef, I'm always looking for new, unknown, reclaimed, or forgotten food or ingredients. Duck eggs fit many of these descriptors.
Prized by bakers for their superior protein content and richness, duck eggs are almost never seen in grocery stores. Fortunately in San Francisco you don't have to keep your own ducks to acquire them. You can find them, if you're early enough on a Saturday morning, at Haney Egg Ranch at the Alemany Farmers' Market in flats of 20 for $12.
They're larger than most chicken eggs, similar in size to a "jumbo" chicken egg. They're off-white with a tan tint and a slight opalescence which creates the illusion of translucence.
Their shells are thicker than chicken egg shells, but they cook the same way once you crack them. Soft boiled, poached, or over-easy highlights their flavor best.
Duck eggs have a richer, denser yolk than chicken eggs; it's almost custardy when cooked. However, the whites cook up to be a bit more gelatinous than chicken whites.
They're basically a straight substitute for chicken eggs in recipes, though you'll need to treat them as jumbo eggs for picky recipes. You can see a conversion chart here.
I use them primarily for baking and breakfast: waffles, pancakes, and omelets. They work fine as fried eggs too, but that's where the gelatinous white is the most evident. They're nothing in comparison to ostrich eggs though, but that's another (and less appealing) story.