In general, can I substitute egg species for either egg-only or egg-centric dishes? (Prompted by an interesting radio show on ducks and duck eggs).

For general uses, in either an egg-only dish, or an egg-centric dish like a custard or quiche, can I use eggs other than chicken eggs?

Other than the obvious that the volume of the dish will vary, and perhaps the cooking time, can I make a fried quail egg on toast, or a duck egg quiche?  Or for that matter, to echo another recent question, a soft-boiled ostrich egg - presumably with lots of dipping toast!
More or less, yes. Just know that eggs of different species have different "flavors." There may be some issues with substituting in dishes due to varying fat content of the yolks and such...

I've had duck and goose egg quiches. I've had fried quail eggs on toast. I have yet to try an ostrich or emu egg.