The following information is the holy grail of successful Budgerigar Breeding. It is only conciously known by a relatively small number of the worlds greatest breeders, but subconciously many successful breeders adhere to these rules. Much of the content of this section of the website has been reproduced and modified with the kind permission of the original author - Phil Hodgkins.
When you visit a long-stablished breeder, their birds will tend to be similar in many ways - they will have been inbred to a degree and will have many genes in common so their appearances will be alike. This is what you should also aim for - but only for desireable features. These genes these bird have will be inherited recessive, dominant or sex-linked and to establish them through out your own stud, it will be easier if you know their method of inheritance. This means that you can apply the three rules of inheritance; dominant, recessive and sex-linked; to breeding that beautiful Best in Show bird.
To establish what inheritance rule applies for each factor can take a very long time - it may take several years before you have enough off-spring from particular pairs to see a pattern. There are a few things to look for that can shorten this period:
To do this, you will need to keep extensive records - the characteristics of each parent and off-spring.
When you have established the rule for a characteristic, you can use the rule to either spread it across your stud (e.g. large spots) or eradicate it (e.g. hinged tail).
Unfortunately, there are many features of a budgie which are affected by many genes, e.g. the general shape/size of budgie, but you can still isolate many features that may rely upon a single gene (spot size, spot shape, number of spots, etc.).