Indeed, they do start out tiny and fragile. I mean, they are still tiny when they grow up, but they're a bit less fragile.
Zebra Finches are one of the hardier species, which may be surprising because of their size (though I have noticed that the smaller species tend to be more well adjusted, for some reason).
Carolyn, I looked at that forum. The person has great pictures of the growth process, but what intruiges me is specifically the picture of the chick next to one-day-old chicken.
It is adorable, yes, but the person says that the chicken hatched from an egg at Trader Joe's.
It's just like: "What?" I usually get my eggs at fries, though it would scare me, if I were to open one, and there would be a developing chicken inside.
I'd imagine the egg was bought while the embryo was at an early stage, and somehow survived being refrigerated (probably recently stocked at the time).