Egg abnormalities are a normal part of chicken keeping. You’ll see odd shapes and sizes, color variations, even eggs within eggs.
Very small eggs without yolks as well as regular sized eggs missing their shells are often referred to as “wind eggs” or “fart eggs”. Apparently this originated from an old belief the eggs were a result of being impregnated by the wind rather than a rooster.
Notice the size of the eggs below. The two larger eggs are normal in size versus the tiny wind egg:
According to Merriam’s Dictionary, a wind egg “is an unimpregnated, addled, or imperfect egg; especially : an egg with a soft noncalcareous shell.”
Wind eggs can range from a normally sized egg without it’s shell (it still has a membrane holding it together) to tiny, usually “yolkless” eggs. Sometimes people refer to the eggs without shells as “Rubber” eggs.
While wind eggs are considered a fairly common event I’ve only seen the tiny, yolkless kind twice in three and half years of keeping chickens. I’ve had hens who periodically lay the eggs without a shell. This can usually be remedied by providing free choice calcium but that’s not always the case. I have one Easter Egger hen who has never laid a normal egg, even as a pullet. She’s a great layer but her eggs often have weak shells, large calcium deposits or are missing their shells. No amount of calcium can fix her, she has an internal glitch. Hens like this can have normal, healthy lives but it’s important to monitor their vents for prolapse or irritation.
Wind eggs are nothing to panic about. If you know who’s laying them it’s good to monitor that hen but typically this resolves itself quickly.