Rare egg within an egg found in Northland - we're not yolking!

The egg was found inside a much larger egg. Photo / Supplied

This rare egg within an egg was discovered by a reader who sent a photo to the Advocate.

The smaller egg sits entirely within a much larger eggshell, with extra albumen (egg white) around it.

An egg within an egg happens when a fully-shelled egg gets held up in the oviduct and one of two things happens - either a complete egg, including yolk, is combined with one large shell or the original egg gets another coating of albumen and another shell.

It is different from a double-yolk egg, which occurs when two yolks are released at the same time and combined within one shell.

This can be an issue for certain breeds of hen and for young hens just starting to lay.

Around one in 1000 eggs are thought to be double-yolkers, but eggs within eggs are a rarer occurrence.

The unusual phenomenon up close. Photo / Supplied