but yes, he is rare. Only about 6 out of 1000 calico cats is male, and most of these are sterile.
This is because (I hope I have this right) both the red and the black color genes are carried only on the x chromosome (called sex-linked), and both are dominant. Therefore, if a male cat has any red in his genes, he will show the red on his coat. This is because there can only be one color gene per x chromosome, and males have xy cells.
Females on the other hand, have xx cells, and so can carry red on one, and black on the other. Since both are equally dominant, both show up in the tortoiseshell pattern (or calico if white is involved).
The reason most calico males are sterile is because for it to occur, there must be two x chromosomes per cell, making the cells xxy. This means the cat is a hermaphrodite, having both male and female sexual organs, often neither of which work.
Hope through some miracle this is clearer than mud. Maybe someone else can explain it better.