Birds have nucleated red blood cells while mammals don't, which made me wonder about this question. I read that birds are easier to clone than mammals, because in mammals you have to look for a white blood cell, which are rarier than red. Is that true? I never got around to understanding cloning and bioengineering, but I thought I might as well ask.

Neither chickens nor any other kind of bird have been cloned yet.

So far, mice, rats, rabbits, cattle, pigs, sheep, goats, deer, horses, mules, cats, and dogs are the mammals that have been cloned.

Closing uses epithelial cells and not red or white blood cells.

see
http://www.fda.gov/AnimalVeterinary/Saf … .htm#Myth9