Of the 5 species of lovebirds kept in Australia,the Black Masked Lovebird in second only to the Peachfaced lovebird in terms of aggression.They are best bred in a colony set up,but fighting can occur which will be fatal if the birds are left to their own devices.It is best to introduce Masked lovebirds at the same time,and to allow 5 nest boxes per 3 pair of birds.Masked Lovebirds take a bit longer to establish as a breeding colony,but once established,they are prolific breeders.They reach sexual maturity at 6 months of age,but are better breeders in their second year.They continue to grow for 2-3 years before reaching their maximum growth.The wild form does have an orange tinge between the black mask and yellow bib of the bird,which has been said by some breeders to be a result of hybriding with other birds.I don't believe this to be true as it molts out in the birds second or third year and birds in the wild go through the same process.
I no longer keep mutation Masked Lovebirds,instead preferring to keep Pure 100% Black Masked Lovebirds in the natural wild form (split for nothing).There are only a handfull of breeders in Australia that do this.