A difficult decision for many of us fanciers is how to match our birds for breeding to try and get the best results. Because there has been no new blood introduced to my family for seventeen years it gives me a tight gene pool, therefore I have to be very careful as to how closely related I can match up the pairs, but with accurate records it is still very much achievable to date. To match my pairs I use a system known as (C.O.I) which is short for what is known as the Coefficient of Inbreeding. It is a system similar to which is used by the Kennel Club for dog breeders finding the right bitches for their dogs and vice versa. It measures the common ancestors of the sire and the dam that has been selected for mating. (C.O.I) can be very confusing and difficult to understand so I will try and explain how I use my system in a simplified way.

As we know, all of us have a family tree and so do our birds. Two Parents + Four Grandparents + Eight Great Grand Parents and so on, doubling up with each passing generation. Some people call this data a binary tree or a pedigree. I use a five generation field for my records which lists sixty two ancestors when matching a pair of birds.

When we match related birds together, some of these sixty two ancestors will appear on both the sires’ and the dams’ side of the family tree and become known as common ancestors. When these common ancestors appear the family tree stops growing. An example being that there might now only be three individual grand parents instead of four. When this happens it is known as pedigree collapse because there are less individuals listed in the family tree than there would be by the continuous mating of unrelated birds.

Below are a few examples of pedigree matching of my own birds, (except for example one), with the common ancestors showing in red segments.

Example 1 is how a pedigree will look using (C.O.I) with continuous matching of unrelated birds.

Example 2 is how it will look when matching brother and sister.

Example 3 is the matching of cousins.

Example 4 is the matching of birds from the top and the bottom of the gene pool.

I have no idea how genetically dangerous it is when matching closely related birds but I think fertility and mortality would be the danger areas to consider, so for safety I do not allow my pedigrees to collapse beyond (75%), which means I am allowed a maximum of forty seven red segments from the sixty two showing on the match sheet. I like to have the white segments travelling through all five generations without being blocked by red on at least one side of the pedigree. If they hit a wall of red segments on both sides I do not allow the match. The above pedigrees are typical examples of how i use my system.

Example 1 is continuous out crossing. Example 2 is a definite no go area for me. Example 3 is as close as I dare go because it’s border line and Example 4 is very safe.

Below are two examples of pairs I put together in 2019.

Pair 1

This pair produced nine eggs over two rounds resulting in only two chicks being raised to maturity. The rest were infertile and dead in shell.

Pair 2

This pair produced nine eggs over two rounds resulting in all nine being fertile with five first round chicks all being raised to maturity but the second round eggs were not required to hatch so they were withdrawn.

The results of the two examples above show me that too many red segments on the pedigree match sheet could spell danger with fertility and mortality.


I purchased my system many years ago from a company called East Coast Software but I am not sure if it is still in production, but if you search the internet for cage bird management systems, similar items can be found. A useful tool to have at hand as it saves hours of study and paper work so well worth a purchase. 


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