In the seven years we have been keeping backyard chickens I've never seen an egg as small as the two pictured above. Not in our nesting boxes anyway. Our daughter did a Google search for tiny eggs and here is what we learned about these mysterious mini-eggs!
One of your hens may be very young. For the first few weeks pullets are beginning to adjust their internal " egg factory". They can produce thumb sized eggs called peewee Eggs. They are perfectly good to eat, but usually have no yoke and sometimes these small " practice eggs " are are empty. It's possible a bantam breed of pullet will also lay pee wee eggs.
Naturally we had to crack them open and see for ourselves. They were yoke-less but not empty. Each egg did have egg whites. One thing we are sure of is that it is most likely one chicken laying the peewee eggs. They are both the same color and Easter Egger's lay the same color egg all the time. Peewee eggs can also be used for pickling. Typically a peewee egg weighs around 42 grams. Peewee eggs are generally not sold in groceries or supermarkets but are often given to bakeries and other establishments involved in food processing.
For more backyard chicken info go to here to read up on Chick Days at your local TSC ( Tractor Supply Company )
I'm linking this post to a darling blog I just discovered! Little Farm in the Big City