maz wrote:(rats are very resistant making inbreeding relatively safe)
This resistance is what makes them so successful in being able to survive in a multitude of climates and habitats.
In similar terms I would think the Zebra would be on a par, resistance wise, so I would think they could probably be quite closely inbred.
I think with inbreeding in the way you described with a less resistant species you would really have to be ok with large scale culling should something nasty pop up.
Granted, it may bring out the best hidden genes in a given flock but you would have to be prepared for the worst too, and have the stomach for the wholesale culling that might have to be done.
Surely the worst aspects could be avoided and the good points enhanced with considered line breeding?
I totally agree that breeding records should be kept, even more detailed in the event of inbreeding or line breeding. Memory just cant be relied upon in this case.
I think parent and youngster pairing is ok,
if a specific trait is wanted
and other sources had been considered first, as long as the young produced from that pairing will be paired with a bird from a totally different source.
I wouldn't like to do sibling pairings. Bear in mind that my previous frame of reference regarding breeding was the dog show ring and this kind of pairing would have been frowned upon.
But having said that Gregor Mendel, is supposed to have bred mice, brother to sister for 40 generations without any noticeable difference except the increase in size. But, as we all know

mice are a resistant species.
In a species that I only have a couple of pairs of.
In my case I start off with two pairs from different breeders/location, this way I can make unrelated pairs so that I have the ability to mix up the youngsters in a later generation. When selling the young I try to have unrelated pairs, even holding onto birds for quite a while till I can get the right pair to sell on. When new blood is needed I buy another pair, hopefully from a different breeder than the original pairs and split them up to pair with the birds I already have.
With my gouldians
This is the species I have the most of. I have birds from several locations acquired over a period of time and this is allowing me to still use the adult birds I have without having to in breed apart, from one instance where I just couldn't get a clear YH headed Gouldian hen to put with a YH cock bird. So that particular pairing was parent and young.
Personal criteria for choosing, keeping.
The criteria I look for depends on the species, but after a healthy looking bird, bright eyes, tight feathers and clean vent, and no clicking or raspy sounds, I then go on to choose based on further personally preferred criteria.
With the gouldians I like a nice rise above the beak, no wing feathers crossing over each other on the back, and wings held up tight and close to the body. Also the tail held out and down, not like a wren carries their tail. With the white chested mutation, I like the white to be just that, white, no patches of blue or other markings. Head colours, I prefer to have no splits. Hens head colour must be clear, not keen on the ones with lots of black mixed in.
Not every clutch works out how I would like to be but where is the challenge if it did? Also those that don't work out are still perfectly acceptable birds, after all beauty is in the eye of the beholder.
In some ways I like the fact that there isn't a "standard" for a lot of birds like the Kennel clubs have imposed on dogs. Even when there is a standard it still boils down to one judges opinion over another judges preference.
These choices when a competition trophy is at stake regardless of the animal or bird being shown make it possible for certain traits to become "over produced" often to the detriment of the creature concerned.
I for one would hate to see that type of "standardisation" enter the bird world.