How do you know if a blackbirds eggs are addled?

Most duck eggs are larger than a chicken egg. PoultryTalk's Response: Smell the egg, duck eggs have a scent chicken eggs dont. Also most are glossy and sometimes they are a greenish color. Also duck...

Same way you know when your having a baby (human).

egg (ovum together with its shell or outer layer)

i would think, that you should rather break it into a dish if it smells it's old if you break it and it has feathers it's old and if ya break it and the colour is blackish it's old and lastely if...