In 2017 I was contacted by the owners of ‘Aviario Gonzalez Pradas’. They had a pair of two blue Agapornis personatus. In the first nest there were to their surprise three blue and two green chicks. When they announced this on the internet, almost everybody was laughing. For most breeders this is impossible.
And indeed in 99% of all cases the offspring of blue x blue will be blue, but there are some situation where the progeny phenotypes do not match the Mendelian principles. We know now that genetics is a lot more complicated than Mendel’s laws (genes and alleles), some cases of genetic inheritance can be far more complex than simple Mendelian inheritance.
So this is indeed possible. It is rare but it is possible. It is no joke!!
We are working on this, we collected DNA from these birds and we are hoping to get more answers in the future. As soon as we have more info available, you will read it all in the BVA-International magazine.