I am just curious as to why you would keep them seperated? Cockateils are very social birds and can become very depressed if kept singly. I have raised cockateils since I was 9 years old. If you are home most of the time then I wouldn't worry about the bird but if not it is advisable that the bird have a playmate. Also the information that you have on a certain color determining whether one is male or female is wrong. The only way you can tell whether you have a male or female is to have the bird sexed at the vet. I have several females that look like your so called male cockatiel. The albinos don't even have orange cheeks and the male and female look identical. I am not trying to be rude, if I come off that way I am sorry. Also females also mount males so this should not be used to determine sex either.