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Fertility Maintenance

Parrot, Please find attached a theory on improving or maintaining fertility while breeding ones birds.
I have based this on my own experience, what I have read and what has worked for me.


Poor reproduction and infertility is a problem that most breeders will run into if they become impatient with small gains towards the standard.  In some instances the breeder will use the first outstanding offspring regardless of its history.  It makes no difference to the breeder if the bird comes from a nest of two or three chicks.  The bird is mated, as soon as it is mature, to multiple hens in order to transfer his good characteristics among the flock.  The chicks are all right, but not the phenomenal birds the breeder was expecting.  A few generations later, after having fallen for the good looking birds with hidden faults and diverting from the breeding program, the breeder notices that almost all of his hens are laying  2 or 3 eggs, with only 1 or 2 hatching and fletching.  The breeder may or may not realize at this point that trouble has arrived, and his or her departure from the breeding plan has led to infertility, low egg production and potentially poor quality offspring as more generations pass and gene combinations are drastically reduced.  This is not an inbreeding issue or a sterility issue, it is the fault of improper selection criteria, and improper application of the tool (inbreeding).  Infertility or sterility is a dead end if grounded in chromosomal incompatibility.  Just about anything else may be managed.

Infrequently a new mutation will occur and a breeder will focus on close breeding and heavy culling to improve the overall repeatability of the mutation.  Observers will suggest that his approach is absolutely wrong, and that he must immediately move to mate the new mutation to a wild colored bird,  thereby introducing strength and health.  This, purportedly, will prevent inbreeding and the downward spiral to infertility, dead-in-shell and finally sterility in his birds.  Others will say that you should not breed back to the parent types because the mutation needs to be assessed (dominant, sex-linked, recessive, co-dominant etc...) and one can only do that by going outside to a strong bird that is unrelated to the parental line.

Going outside the line is problematic for a number of reasons, including the unknown nature of the mutation, its transfer mechanism and statistical probability.  Several  reasons that lend credence to inbreeding are:  1)  Depending on the mutation mechanism, the most rapid way to identify whether a mutation is dominant, recessive or sex-linked, is to cross it (them) back to the parents;  2)  That the use of inbreeding, an old-fashioned or un-educated position as some would call it, is based on mathematics: A mutation occurs by chance, so one only need look at the possibility or probabilities of that particular gene alignment happening again in the same birds. This in turn helps to determine the intrinsic value of separating the parents and mating them with their offspring or keeping them together;  3)  Any outcross to a wild type bird with a fully heterozygous genome could mask or interfere with a mutation and its expression, after all it happened by chance;  4)  A back cross to the parental generation will enable the breeder to determine which sex (if sex-linked) carries the mutation or whether the mutation is dominant or recessive (determined by phenotype and statistical presence of mutation);  5)  The genome similarity, if the mutation occurs in a line bred or closed breeding program.  In this case the parental and the mutation bird's genotype will be relatively similar, as compared to heterozygous, non select birds.  This in turn simplifies the establishment of an autosomal recessive mutation, as most new mutations are recessive to already established recessive mutations. The only challenge to this thinking is where a mutation is sex-linked and the hen offspring may reveal the cock's hidden chromosomal change (the mutation occurs in the cock's germ cell during early development, but is not expressed in its phenotype):  6)  That inbreeding can substantively improve or concentrate gene inheritance where a foundation sire or hen exists, and the breeder is seeking to aggregate desirable genes from the hen or cock, in the offspring;   7)  That a breeder with an established or developing varietal line or breeding program, would want to ensure that the new mutation carried the same desirable (homozygous) traits.

Inbreeding has developed a bad reputation from those who have not really practiced the art, or have selected poorly.  Some birds will naturally lay fewer eggs and have more dead-in-shell or infertile eggs, but it is the breeder's responsibility to manage that problem and prevent it from spinning out of control.  Some readers will jump to the immediate conclusion that the previous wording translates as "inbreeding leads to infertility and sterility".  It does not.  The selection criteria and methodology does.

Despite the derision for inbreeding, that seems to dominate the avian world, the evidence surrounding the success of inbreeding as a tool for hastening change and improving or engineering a discrete population's characteristics, it has held its own in the avian world.  The practical and tangible evidence for inbreeding success directly opposes those theories or perceptions of inbreeding as a waste of fertile birds, genes or anything else that people have tried to suggest.

Species failure in the wild could not and would not be offset or replaced by a few domesticated birds.  Any full scale species decline or loss suggests that something has impacted their environment in a way that nature has not anticipated or selected them for.  Please don't blame current avian enthusiasts.  Damage, if it was done, occurred early in this Century and would have been associated with large scale exports and economic depression in a number of countries.  Today, the few exports that occur cannot hold a candle to the exports of the past

Unfortunately, science is oft used as the leveler or spoiler in disputes over inbreeding.  If a mathematical or scientific method or formula does not provide consistent results or is not repeatable it is not good science, and therefore is unacceptable as a scientific method or so the theory would go.  This then, identifies why an individual can have such consistent success with their inbreeding or hybridizing programs, while others, who believe they are doing the same thing, fall into all of the traps.  The assumption is that all individuals are focusing on the same objective, but it is equally clear that something, predictably, goes wrong in trying to obtain the objective.  This is very similar to someone creating a delicious recipe for a cake, but the recipe that is passed on does not include the vital ingredient required to make the cake as moist, as tasty or as firm as the original.  Is this simple little example synonymous with the problems encountered in applying breeding and fertility selection processes ?

Overall inbreeding methodologies may be similar in turns of selection and pairing, but one or more steps are rushed, and the breeder undergoes several years of intensive selection and pairing before coming to the unhappy realization that fertility is dropping and an outcross is required: the kiss of death to an inbreeding or varietal program, where the goal is, arguably, the cloning of color and form of a desirable or concept type.  Is it possible to conclude from this that it is not the methodology that fails, but the application in the hands of an impatient or inexperienced individual or breeder ?  The method is sound, and many books refer to the process and success of inbreeding, but it seems that certain basic tenants are ignored in what is now seen as a complicated polygenic inheritance game (inbreeding), with little flexibility and disastrous implications: therefore, the best response for aviculturalists is a non response: better to keep it quite than spread misinformation or solve the inconsistencies.

What we end up with is a method that works, and as you state on your pages, it is hampered by a resistance to education or open discussion on the topic.

All of this says that people engaged in certain endeavors require specific understanding or knowledge in order to operate in that environment.  Most of those instances where something goes wrong in inbreeding are associated with those who have not been inbreeding long;  who really don't have a line or variety or any experience in developing one, but believes he or she can immediately begin inbreeding with their two or four birds (instant expert).  Are you beginning to get a picture as to why the the novice or untrained breeder may not be very successful, and why birds are made to suffer as a result of the lack of information out there ?  Education and the transfer of knowledge is key to preventing or reducing loss of life and congenital aberrations in our birds, but there are few who seem interested in hearing or wanting to believe it.  The result is continued contamination and mistakes in our perceived "pure' stock.

Inbreeding in Hybridism

If you are fortunate enough to have a hybrid bird that looks "pure" (95%), you may not be able to tell you have a hybrid.  However, once the bird is introduced it means that your flock is going to be "contaminated".  A hybrid will pop up at some point, and these occurrences will increase where there are no pure stocks to cross back to.

The breeder may not have the will to cull birds that don't look quite right, or exhibit a color, where there is not supposed to be any.  Unfortunately, the lack of information surrounding the background of the bird means that a "true mutation" is lost because it is seen as a hybrid result or combination hybrid result.  After all, which genes are crossing or swapping to create the new look: original or hybrid?

Only an absolutely clear understanding of species standards in the "wild" will help people to recognize what is pure and what is not.  Unfortunately, even that is complicated by natural or wild hybridization between species.  A variety, in my opinion should not be used as a standard for a wild species, as the variety may skew the scale towards hybrid acceptability (where a variety is based on a hybrid introduction), without taking into account the overall impact of the color.  Expectations may move towards the variety, and cause the original, wild bird to appear smudged, dull or imperfect by comparison.

Hybrids need to have more attention focused on them by Avian societies and advice should be available to newcomers / novices on how to cross and maintain them, while taking action to prevent inadvertent, wide scale mixing of genes and the confusion it can generate (we may be there already with some species) among non hybridized domestic populations.  Domesticated hybrid colors and forms are created for two purposes: 1) because the person can , and   2) because they are highly desirable for shows and color.  They are also a very important development in human history and its success.

Recognizing hybrids will help people to understand what they have and hopefully reduce their impact.  However, how do you maintain a hybrid if all of your "pure stock" actually compromises genes from another species gene pool.  Even at 90+% purity, these birds are hybrids, and lets not forget it.  The public-at-large still needs to know what to do with these birds.  What do you think ?   Should no one tell them that once they cross a hybrid with a pure mutation, any offspring from that union will carry hybrid genes ?   Has anyone contemplated or performed a mathematical calculation (algorithm) to determine the number of hybrids it would take to "pollute" a discrete population, over a definite time period, if the hybrid was fertile.  How does that translate to hybrid mutations impacting any species out there today ?

Knowing all of this, can dedicated breeders and professional aviculturalists remain quite about hybridism and the necessity for inbreeding inclusion when establishing a line or variety.  Inbreeding is, in many ways, the antithesis of hybridism, although it is also highly dependent on inbreeding:  Inbreeding goals target a homozygous state in a particular species.  Hybridism utilizes the homozygous donor species for color transfer or transmutation, but once achieved, makes every effort to cross the hybrid back into the wild or varietal, color receiving species.  Crosses are continually made to the best of the species ( as defined by exhibition birds), and these are often birds that have been selected for years and reveal the "defined" characteristics of the species, although complimentary genes may be quite different from the heterozygous, wild species.  Unfortunately, crossing hybrids will result in greater percentages of hybrid offspring or offspring that can appear quite different from the "parental stock" after a few generations of inbreeding.  It is understandable why those who have supported hybrid additions, are opposed to inbreeding practices that could confirm the hybrid nature of a particular "mutation".

What Avian organization do you know that has posted clear shots and a close up of the specialty, wild type species on their web pages: back, front side, head, wings underparts and rump ?  NONE.  Why ?  This should be the first step, where hybridism is abhorred.  However, it is not done.

For that matter, what club or organization has produced clear close shots of those bird mutations identified as winners in different shows?  NONE.  The pictures are obscured by bars, the color is difficult to see because of lighting, the rumps and underparts are not visible and the most contentious areas are often hidden in the shot.  Is it any wonder that people don't know what they should be breeding for. Look at the simple confusion surrounding what constitutes an acceptable fischer.  How can a "normal" Fischer compete with some of the mutational colors and varieties out there, when some may not be sure what a wild type fischer is supposed to look like ?

If one looks at the budgie, they can quickly see that the size is not all that has been lost in the pursuit of larger birds.  The entire form or structure of the bird has literally changed.  Gone is the straight back, the strong conformation, clean lines and wing carriage.  The bird no longer looks like a budgie.  Standards need to be maintained and established for new types or else anything goes.  If anything goes, there is no challenge in breeding and the hobby falls into disrepute. Everyone has an opinion, but the judges have a clear standard to follow, and if the bird is larger, it should be recognized for the full host of attributes and not just size.

Known Theory / Application

The most common inbreeding methodology sited on web sites and used by bird breeders is the replication or concentration of the cock's genes in its progeny.  In one sense this optimizes the benefits of the male genome and clearly identifies the cock as the most important bird in a pair (this is unquestionably incorrect, but we will come back to this later).  The cock bird is the homozygous (ZZ) individual in the bird world, while the female is the heterozygous (ZW) one.  The cock can mate with multiple hens and pass on its desirable genes to numerous offspring very quickly and thus is, economically, more valuable.  The cock carries its mother's Z chromosome: This chromosome is thought to impart or at least express a measurable impact on size and egg production.

The cock's, sire's Z chromosome may impart conformation and head position (angle), which is important in the overall structure and stance of the show bird: One of the cock's two Z chromosomes are passed on to each female offspring in a randomized fashion, and when youngsters are mated back to their sire, a recombination of the sire's ZZ genome is the goal.  As matings are repeated over generations, with the best hens of each generation being back crossed to the foundation sire, more and more of the offspring will come to resemble that sire (and if everything goes off without a hitch: prepotent animals develop), and carry a large percentage of the cock's "blood" or genes.  Performed incorrectly, however, it is probably more realistic to expect productivity to decline, and more infertility and dead-in-shell occurrences with inbreeding activities.  Again, all of this points to the cock as the most valuable sex, based on its juvenile and adult capacity to produce offspring with multiple hens.

A contrasting position is that the hen is the most critical animal in the pair.  It is commonly held that the female will pass on size and a few other important physical or structural elements to its offspring.  The hen offspring are also held to express the phenotype of the cock, while cocks look more like the foundation hen: This is particularly noticeable when there is a sex-linked color mutation.  The overall health and vitality of the hen is absolutely critical, and this cannot be stressed enough.  A healthy hen is an absolute for the successful production and development of egg and embryo.

The production of the egg is often taken so much for granted among birds and breeders, that it slides under the radar of many.  After all, if a bird did not lay eggs, and the eggs were not fertile, we wouldn't have birds.  So, as ridiculous as this all sounds, it does not matter one whit how nice or valuable your cock bird is, or how virile it may be, if any part of the hen's reproductive system is damaged or unresponsive.  That damage may impair or neutralize the genetic material provided by the donating cock or negatively impact some other stage of early development.   Similarly, if the hen is unwilling to accept a cock or seems extremely selective about her mate,  success will be limited.  The reproductive organs do not need to be anything special for egg production, but they do need to be capable of normal activity and functioning properly.  It is when a hen is in poor condition from a lack of food or nutrients, from excessive breeding, that she will be unable to absorb the required elements or nutrients to generate shell thickness or perhaps form a yolk.  These deficiencies can, in turn, impact muscle strength and other organ function.  The hen needs to be healthy, and because of her value should always be provided for in the best fashion available.  In my own experience the hen has always been more important than the cock in forming a line.

Health can be defined by an exhaustive list, but foremost in assessing it, is hen size, form and stance, the number of eggs and their fertility.  The conclusion here is that the hen has to be in optimum ("normal") health in order to perform her function.  We all know the basics:  Healthy birds produce healthy youngsters. This being said, the hen is equally important as the cock and sometimes more so.  However, she will give up a year to the cock in terms of breeding offspring and numbers.

If the hen is to be the founding bird in your strain, the issue rapidly becomes how to increase the productivity of that hen and optimize her gene dissemination  Unlike the cock, she has a limited number of offspring per year and a defined number of nests, if the breeder is performing his job properly.  She can have multiple partners over the year (cocks = nests), but she cannot be crossed with as many cocks, as a cock can be crossed with receptive hens, in a one year time frame.  This means that the cock has a greater chance of "clicking" with a hen and producing outstanding progeny, whereas the hen is restricted by her breeding and care limitations. Just as a breeder would not want to put a poor or sickly hen with a foundation cock, neither would the breeder wish to pair a foundation hen with a sickly or indifferent cock.  A superior hen that lays three eggs, has two fertile eggs and one fledgling with a superior cock,  should be subject to a reassessment in your program, no matter how good she looks.  Conversely, a mediocre looking hen may produce 6 to 8 eggs per nest, hatch 4 or 5 excellent chicks and fledge 4 or 5 with a poor cock. Which would you keep ?

What is apparent from the variety of experiences with inbreeding, linebreeding or close breeding is that breeders are commonly selecting for cocks that are the best in form and color, but not necessarily for hens of equivalent value. They seem to think the outstanding cock is a good trade off for fewer eggs and chicks in the nest (or so the breeder is stating by selecting an inferior hen).  Unfortunately, this road can take him quickly down a path that is very difficult to back up on, and one can see where the lack of prolific egg laying will eventually lead to fewer eggs and sterility.  So how might a breeder theoretically address infertility, the perceived end result of inbreeding ?


The interesting element that ties budgerigars, lovebirds, finches, pigeons and lovebirds together is the inbreeding selection methodology touted throughout the "Web".  The breeder starts with the most desirable pair he can afford, and which reveal the characteristics that exemplify the standard.  These birds are bred together and the cock bird is mated to his first generation offspring (F1): the F1 hen showing the desired characteristics.  The result of this mating is an F2 generation. Once again, the best hen from the offspring is mated back to the foundation sire, and on, and on it goes.

Some would call this inbreeding in the 1st offspring generation, but linebreeding or close breeding, in later matings where the best hen in each successive generations is bred back to the foundation sire.  This can lead to a host of problems, but the most common is reduced fertility, and reduced offspring size, depending on the selection criteria and the unearthing of hidden autosomal recessives (sometime deformities).  The manifest problem at this point is a line of birds, looking very much as the breeder desires, but having begun a nasty spiral downwards towards eradication: fewer eggs, low to zero fertility and deformities among the young, where eggs are fertile.  Most breeders will look to go to an outcross at this time.  Unfortunately, this has a significant detrimental impact on the entire breeding process and can take you back to ground zero.

There is nothing left to the breeder, except to out breed when they reach this point.  However, there may well be an alternative to dealing with this problem and preventing the situation early in the process.  This step will delay your actual foundation stock selection, but is well worth the effort, as far as things go.  What is it ?

Hen The breeder, with purchases in hand, crosses the hen and cock and now looks to the hen offspring to assess the value of the cross.  He crosses as many juvenile hens back to the cock as possible in order to determine if the hens are equally productive, or if some are better than others:  they will excel or fall behind in egg production.  If a hen fails to attain expectations, sell it.  If they excel in egg production, and one would expect fertility, retain them.  This will ensure that the hen "line" will continue to be productive and not lead to mis-steps in the selection and breeding process.  Benefits will be passed onto the cock offspring and assist in maintaining egg production.

One of the greatest challenges is to ensure that the breeder does not get carried away by the occasional exceptional bird, but continues to keep to a rigid doctrine of selection based on female egg production and fertility, and similarly the use of replacement cocks, where necessary, from parental stock where egg and nestling numbers are at or above target levels.  If the exceptional bird meets the set or standard requirements for selection, by all means utilize it.  If it does not, the breeder has to force themselves to ignore the bird, despite its inherent aesthetic value, and keep moving forward with small gains.  If the bird cannot pass on valuable genes within its own select family,  it is of a highly questionable value to the breeder.  The challenge is always to remain focused on the initial objective and keep on moving towards it, instead of being diverted by a spectacular bird that can undermine breeding gains.

Some will try to say that you should be looking at only three to four eggs in a clutch, so that the hen is not overworked.  You have to foster any more than two or three chicks anyway, with showbirds, so why look to increase rather than maintain egg production levels.  Unfortunately, the 3 to 4 egg production target can and will, inevitably, lead to the problems so many breeders encounter with decreased egg production.

The high target is an important factor in getting through autosomal recessive characteristic inheritance or lethal gene combinations.  Continued assessment of cock and hen fertility should ensure that progressive loss of fertility over several generations does not occur.  It all seems relatively straightforward, but just a few birds of exceptional quality with poor reproductive capacity or low activity levels can quickly undermine years of gain and effort.


Inbreeding is a tool like any other and it is the lack of education around its use and application that leads to the horror stories that seem to so tightly adhere to its spoken or written use.  Sterility cannot be overcome if it is a chromosome linking or compatibility issue, but fertility and offspring can be maintained by ensuring target egg levels and fertility are maintained.  Some recessive characteristics may raise their head and interfere with hatching, but the larger the volume of eggs in each nest, the greater the chance for producing a bird or birds that do not carry the gene, and can keep the line productive.  Even these few birds will have to be held to production levels, to ensure rapid re-population of potentially diminished stock during these infrequent occurrences.

You often hear stories of people bringing in birds and of successful breeding efforts, that are soon replaced by inexplicable and staggering losses.  However, during the active production period, many offspring may have been produced.  With a little luck, some of those juveniles or new adults will have experienced small, unobservable or measurable changes that enable them to survive in a new environment, or they die.  Sometimes only one or two or maybe four might survive from a flock of 120 or more.  Fortunately, those survivors have adapted to the environment and they are able to pass on their "adaptive" gene (s).  If fertility was poor or egg production low, inbreeding to raise numbers could see all the birds disappear.  Fertile egg production is an important element in survival.

Look at, and know your birds and their history.  Know the differences in size between hens and cocks in the wild, and their physically distinctive characteristics.  Apply that knowledge to your breeding program and use those birds that are small, if they fit your parameters and you know their history.  Test those birds that you are unsure of, but remember that a bird's physical appearance does not matter in the scheme of things, if it carries deleterious or poor gene combinations.  By all means use the bird for show, but do not suggest that all related birds are genetically identical.   Interesting genes, gene alignments, masking or concentrations may have occurred in an eye appealing bird, but if the bird cannot pass on its genes with close family members, there is potentially, something undesirable happening .  Use only those birds that you are sure of in your breeding program.  Gains may be small, but the homozygous or prepotent target will continue to be approached.  Any undesirable or non complimentary gene inclusion will only undermine that goal and lead to another horror story.

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