Actually, male Calicos don't die easily, but they are born sterile (at least a great majority of them are).

The gene that produces the red color is linked to an X chromosome. Females carry XX and males carry XY chromosomes. To produce a calico, you need one dominant and one recessive gene. Since females have 2 X's (which produce the red), they can carry both the dominant and recessive genes needed to become calico.