What is the birth rate of Calicos Is there usually only one per litter?

Calicos are just ordinary cats with a certain color mix. If you mean the number of kittens born to a calico mother, it's usually 3-5 per litter, the same as for any other cat. If you mean the number of kittens in a litter who are calico, it all depends on chance and the parents.

It takes these 3 genes to make a calico:

--An orange pigment gene from one parent.

--A black pigment gene from the other parent (normal males only get their pigment from the mother, so they can't be calicos).

--A gene to make white patches and separate the black & orange into their own large areas.

So the parents need the right genetic mix. If both parents are missing the black, the orange, or the white patches, they can't have calico kittens. If all 3 genes are available, then luck of the draw decides how many kittens actually do get the full calico combination. It could be all or none of them.

For the technical details, see http://www.fanciers.com/cat-faqs/tricolors.shtml