How likely is it for hens to have twins?

Double-yolked eggs are about as close to twins as a chicken will get. These will not be able to reach full development (without extensive human interference) due to shortage of albumen (the protein-rich egg white) so really the chances are almost zero.

The chance of hens laying double-yolked eggs is a tricky question, because it depends on the age of the bird and its nutritional state. Young hens lay more double-yolked eggs as do well nourished birds.

Hi Samuel,

Paolo may well be right if you mean "identical twins" which develope when a fertilised egg splits. In humans we also have "fraternal" or "dizygotic" twins when two eggs (ova) are fertilised and develop simultaneously. This is actually more common that identical twins.  Actually in chickens a normal clutch size probably averages about 3, so if you think about it it is actually normal for chickens to have triplets! they aren't identical ones though.


Alastair

True twins - two identical embryos that developed from the same egg and were hence contained within the same one eggshell - have been recorded in birds, but I think only once. This was in emus. The fact that it has been recorded once shows that it almost certainly occurred on other occasions, but on those occasions went unnoticed or unrecorded. Clearly, true twins are possible in birds, but very, very rare.