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Hybrids

 


This is one topic that can generate incredibly heated arguments. The issue is whether hybrids birds (the result from the breeding of parents that belong to two different species) should be "made" and if so, should they be sold to the public. I don't claim to have covered all the points of this discussion, by the way.
 
For starters, let's agree on the definition of a species. A species is defined as a group of individuals that are more related to each other than they are to other such groups, and this has come about because of genetic (reproductive) isolation. This is to say that a set of individuals (a population) have been breeding amongst themselves, and in doing so, natural selection, mutation and chance have caused each population to become genetically different from other populations (if there is migration among populations, that will have a certain effect in mixing things up). By "different" I mean that genetically, each population will eventually develop distinct, characteristic frequencies of alleles, with alleles being the different "versions" of given genes. One key reason those populations remain genetically distinct is that the populations do NOT intermingle, and if they do, they trade genetic material at a very low rate (this level is arbitrarily set).

At least part of the confusion comes from Mayr's biological species concept, which spells out that the offspring of a mating among individuals belonging to different species is sterile; this DOES happen in some cases. Unfortunately, in using that definition, people often stick "to the letter of the law" and fail to see "the spirit of the law." In such cases, the fertile hybrid is then seen as the "missing link" that "proves" the unity of two otherwise discrete populations, and the sterile individual is seen as the culmination of a series of genetic steps, the ultimate proof of true separation of the two populations. Yet, equally thorough genetic isolation can happen well before there is the production of infertile young. As long as the populations don't mate, whether that is due to behavioral, physical or geographical reasons is irrelevant: genetic exchange doesn't happen, period! Genetic isolation among populations is THE effective parameter in this discussion, as long as people are willing to define the species involved according to their behavior and geographical range in their natural, UNDISTURBED habitats.

When we take up the discussion of whether two individuals capable of mating and producing viable, non-sterile offspring are the same species or not, we must decide WHY WE CARE about the outcome of the argument. To some people, the relevance hails to their belief that allowing a mating in captivity that would never happen in the wild IS doing a disservice to the evolutionary trajectory of each species/population in question. Alternatively, others argue that the fact that the breeding animals are no longer in their natural habitat already introduced a very chaotic factor into the populations' genetic futures, and that anything else that may happen in captivity and which doesn't directly involve the wild populations is irrelevant to the future of the wild populations. Obviously, the people that support the first interpretation oppose hybridization in captivity, while the others don't. I am not trying to convince anyone that hybridization in captivity is good or evil; I'm here simply trying to summarize the arguments offered by both sides.

There are some incontrovertible facts that also affect this discussion: many populations of wild birds are in eminent danger of extinction due to the loss of their habitat. Even if sufficient habitat was secured and a population was established, population genetics models predict that, unless the population is sufficiently large, it will eventually go extinct due to inbreeding (which accelerates the expression of inheritable characteristics, whether they are good or bad). Another fact is that there are representatives of at least some of those species being kept in captivity, and that some or most of those individuals are capable of breeding.
bullet1. Each bird that is bred to an individual of another species COULD have been breeding with a member of its own species and creating young that can help maintain genetic variability. (Remember that birds must form a bond with their mate, this takes time and is different from the more "casual" mating rituals of other species).
bullet2. Each non-hybridized individual we have is a vessel that stores valuable genetic information. This genetic information may be used in the future to help natural populations recover from the damage that has been done by human intrusion (in the form of hunting, capturing birds for the pet trade, and destruction of habitat).
bullet3. "Pure" (non-hybrid) birds are more beautiful than any hybrids anybody can create. Hybrids are aberrations that were not "meant to be."
bullet4. If hybridization doesn't occur in the wild, it shouldn't be allowed to occur in captivity.
bullet5. We still don't know a lot about breeding birds in captivity, in particular about the nutritional requirements of baby birds, and we may be using nutritionally incomplete formulas. Hybrid birds may have different requirements from what non-hybrids of either parent species are believed to need, and because of our ignorance we may not properly nurture hybrid offspring.
bullet6. There is no way to ENSURE that a hybrid bird won't be bred. Even if the owner swears they won't breed the bird, unforeseen circumstances may come into play. Ask any breeder and they will tell you that many of their breeding birds were formerly pets: that means that a lot of birds DO get passed on to others. The same thing may happen with a hybrid, and the new owner may not be as careful about upholding the promise not to breed the bird.
bullet7. The reports of hybrids parrots occurring in nature are rare, many such matings may have occurred due to human intervention or disturbance of natural habitats, or to people facilitating the mating of animals that would otherwise prefer to mate with their own species. Many such reports are anecdotal and unverified. Also, hybrids are rare and only occur in the zone where the geographic boundaries of two species meet. Hybridization is NOT a common occurrence nor is it part of the "natural scheme of things" in particular when the species involved DO NOT have overlapping geographical ranges!
 
bullet1. Not all birds kept in captivity are capable of breeding. Hand-fed birds in particular seem to have a high incidence of showing no interest in bonding with members of their own species. Even if they were capable of breeding, their owners may not be interested in allowing them to be bred. Because of these variables, it is not truthful to say that each pet bird counts in this conservation effort.
bullet2. There is no unified program controlling the matings that take place in captivity. For the most part, no records were kept of where the initial breeding stock originated, so for all practical purposes we may have lots of hybrids in the pet trade that are believed to be "pure" representatives of one species or another. Likewise, most breeders have not concerned themselves with preserving subspecies. In other words, the populations of birds that we have in captivity have, for the most part, an uncertain background and as such are useless in providing genetic material that can be traced back to a certain geographic region or another. If the anti-hybridization people don't feel these distinctions are important, then they should be just as happy with repopulating the habitats with whatever parrots can be had, regardless of their species or of whether they are hybrids.
bullet3. Beauty is in the eye of the beholder, and some people DO like the coloration of some hybrids. For instance, there are many color mutations in some species of captive birds (e.g., budgerigars) that, although they didn't originate from hybridization, are very beautiful in their own right. Hybridization (mixing of genetic material from two distinct groups or species) has had a place in the domestication of every grain we eat and also played part in the domestication of most or all our farm and companion animals. Hybridization has been a key part of the domestication process and perhaps it will help us create pet birds that are more comfortable and happy in a human home.
bullet4. There are lots of things that don't occur in the wild, like having a veterinarian care for the animals, and offering a balanced diet, and keeping the birds in human homes. Or keeping birds in cages and clipping their flight feathers. Captivity IS an unnatural circumstance, and whatever birds are bred in captivity are NOT "playing by the rules" that regulate the lives of wild birds. Because of this, we may in fact be breeding birds that won't have what it takes to survive in the wild.
bullet5. Hybrid chicks seem to be doing just fine, if they weren't, they wouldn't be for sale and we wouldn't be having this discussion, right?
bullet6. Hybrids occur in nature. Hybridization is natural. Don't accuse me of failing to care for my bird for the length of its lifespan, or of providing for its care if I can't do so, you don't know me, blah blah blah, et cetera.
bullet7. There aren't that many hybrids being created, therefore their numbers don't pose a threat to any "domestic breeding for future repopulation" efforts. Besides, there will be no return to the natural world as it was, so we must start talking about modern evolution, which happens when humans intervene.
The counter-counter argument to that is something along the lines of: "fine, even if all that is true, AND the world is going to hell in a hand basket, AND there is a hole in the ozone, AND the rainforests are gone, not creating hybrids AT LEAST IT DOESN'T COMPOUND ON THE PROBLEM and COULD help preserve species as we know them."
 
As it stands, making, selling, nor owning hybrids is illegal. I think most rational people can see that there ARE arguments for both "pro" and "con." Ultimately, as long as there is a market for hybrids, there will be hybrids. As is, I can't imagine domestic breeders as a whole "saving" any wild populations via their breeding stock because of point #2 above. As long as there is no agreed, encompassing course of action, all we have is a bunch of people running their own breeding and domestication programs, (programs that may include inbreeding, hybridization, breeding of unsuitable or unhealthy birds, dubious record keeping...). Which is to say, the great majority of breeders (and the birds they own and produce) are NOT (and probably CAN'T be) part of pro-conservation army, because more likely than not they are breeding PETS for the pet TRADE, or at worst, are just pumping out a commodity the market demands. Most certainly they are not breeding wild birds meant to be the basis of a re-release program.
 
With that said, I hope people think about these issues before they buy a hybrid bird strictly on its appearance. As is the case with other purchases, people need to decide if they are OK with being part of the pro-hybridization crowd because whenever a hybrid is purchased, the buyer IS supporting hybridization in general. Likewise, let us all remember that the birds are NOT to blame for what is going on. Hybrids deserve as much loving care and respect as any other animal. Their owners likewise don't deserve to be ostracized because (1) they may have NOT been informed they were buying a hybrid (both ignorance AND false advertisement can be to blame on this one), or (2) they may have rescued the animal --meaning, they were not directly, deliberately contributing to the demand for hybrids-- and (3) because, after all, the impact of domestic hybridization on parrot conservation hasn't been assessed [and if it has, and anyone has info on it, please pass it on and I'll edit this section].