PIGEON

Working downward is size is the pigeon.  Again, plain white, small brown specks here & there.  I love Joe's 3-D holder.  It shows such a typical pigeon.  Funny thing is, I too found a pigeon egg one day in a window ledge in an office building, I just couldn't get to it.  Seems pigeons lay were they are. No nest, and no sitting on them to hatch.  Kinda careless, I think, but the then, pigeons are, just look at the top of your car someday.

CHICKEN
Now we come to chicken.  Doesn't sound too exciting, until you start looking up just how many sizes and colors there are of chicken eggs.  The  Ameraucana chicken comes from South America and it lays a green egg or a blue egg and I've seen several shades of each.  The brown egg goes from a very dark hot chocolate color to a very pair, just not quite white egg.  Then you've got you're white egg.  Not any difference nutritionally in any of them, but then you start with size.  The banty chicken, being the "bantum" weight of the chicken lays super small, for a chicken, egg.  Yes, there's one coming up.  Then you go up the scale to JUMBO, and they can be larger than a duck egg.  Commercial graders have laid the size out, so you know what you're getting, and if the recipe calls for a large egg, you had better use it, the results just won't be the same if you use two smalls.  Genetics makes the different colors, and I could make a long list of which breed makes what color, but I'm an egg collector, not a chicken farmer.

Duck

DUCK
To pick one size of duck egg is, well, pretty impossible.  I've seen duck eggs as small as a small chicken egg and almost to size of a medium goose egg.  I'm told that bakers like duck eggs because the yolks are "fattier" which makes lighter pastries.  Wouldn't know, I can't eat egg yolks.  I enjoy and have a lot of duck eggs, they're quite easy to get your hands on, but they are wonderful for playing with.  Check out my tulip made of two duck eggs, it's very easy to find the same size duck eggs, just get them from the same duck.  They have thicker shells, so they cut cleanly, and take to paint and dyes like a "duck to water"  (sorry)