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| LINEBREEDING FOR IMPROVEMENT OF STOCK Copyright © 2006 Linda S. Rubin All Rights Reserved |
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| ORIGINAL BOOK REVIEW by Dr. Rainer R. Erhardt "Well, there is help on the horizon and anyone seriously interested in color genetics should take a look at Linda Rubin's book: COCKATIEL GENETICS MADE EASY! Though this book is primarily directed to breeders of cockatiel mutations, there is enough information in this volume to teach anyone the secrets of dealing with recessive, sex-linked, and dominant mutations..." ACBM, Vol. 65, No.12 CLICK TO READ THE REST OF THE REVIEW! 112 pages, 15 chapters, glossary & more! |
Copyright 2006 Linda S. Rubin
| c. 2007 Nancy Johnson Mello |
| LINEBREEDING FOR IMPROVEMENT OF STOCK ©2006 LINDA S. RUBIN www.CockatielsPlusParrots.com “All Rights Reserved” First published in NCS Nov/Dec 2006 Journal Introduction Although this article does include exhibition stock as its focus, readers should realize that it applies equally to the production of quality companion birds and non-exhibition stock. Aviculturists are responsible for the quality of birds they bring into this world and therefore the goal should be to produce large, healthy, fertile, long-lived cockatiels, whether such birds are destined for a deserving child, a loving family, a hobby aviary, or the show circuit. What follows below is an introductory article to just some of the considerations when improving stock. Is this Normal? A common question I receive from cockatiel breeders is how to utilize a good quality Normal to improve their stock. Yes, an exceptional Normal Grey can help to invigorate a failing or inbred bloodline. However, that is because the Normal Grey selected is of superior quality. Just because a cockatiel is a Normal Grey, does not guarantee that it would automatically be a superior bird. The confusion perhaps stems from those of us who used to breed Normal Green Budgerigars to improve champion bloodlines known to budgie aficionados as “dipping into the green” - even aviculturists working with other species of parrots have utilized the same principle. Breeding the best Normal Greens (or Grey-green, etc.) budgies is known to improve bloodlines because the Nominant Green bird, when exceptional – which it often was - was difficult to beat by any other color. However, this strict code does not necessarily always apply to cockatiels. Indeed, work in cockatiel color mutations among breeders and exhibitors has so improved over the past two to three decades that we now have lines of exceptional Cinnamon, Pearl, Lutino, Whiteface and even Pied primary mutations that could put many a Normal Grey to shame. That does not mean there are no longer any exceptional Normal Greys, quite the contrary. It simply illustrates that Normal Greys are not the only primary color that can invigorate lines and that the cockatiel is not limited to improvement solely by working with the wild Nominant race. Genetic Traits The key to improving existing stock is to determine first which traits are missing and to purchase those traits in appropriate outcrosses from proven sources. Even if you are not an exhibitor, the best way to determine outward, physical characteristics is to place individual birds in show cages, which are designed to exhibit cockatiels at their best, and compare them one at a time, then one-on-one with one another. Study the show standard for desirable traits and check to see how each bird measures up. Sizing Up the Situation A trick when determining size, shape and proportion is to wait until dusk, then view the silhouette of individual birds as dark settles in. The larger birds will stand out; keep these - presuming size is appropriate and satisfactory – but before eliminating any from the lineup consider the overall shape and proportions. Show standards require that proportionally, cockatiels should measure in three equal sections from the top of the crown to the vent – from the top of the shoulder to the wingtip – and from the vent to the tip of the tail, ideally reaching equal proportions, excluding the crest. Now, examine the substance that is a critical aspect of size. A cockatiel should appear sleek and streamlined, yet full-bodied with enough substance through the width across the chest and shoulders (especially in adult hens), from both the front and back view. Next, review overall carriage and deportment. The wings should be large and wide, held tightly and close to the body while blending into the straight backline and tapering abdomen. Wingtips should lie close to the tail without rising above the backline. Flight feathers should be held up tightly, close to the wing, rather than dragging or dangling down. Allow for birds that are tired, because a bird’s appearance can change as it moves around. Don’t worry about perfect feather condition; that is something that can be enhanced should you ever wish to exhibit a bird. You are looking only for outward genetic traits and overall conformation. Lights Up Now, turn on the light. Examine the birds close up and start at the top. Are the heads large, well rounded, lacking a flat top with a pronounced frontal brow-line, creating a proud, “hawk- like” appearance? This physical trait is more important than, for example, perfect cheek patches or white wing bars, which later can be refined once more important traits are embedded. The crest of the cockatiel is its chief, physical trademark. Is it approaching three inches, full and showy, curving back gracefully with the longer filaments graduating evenly down towards the rear of the skull? Is there any evidence of bald spots behind the crest, which is an inherited fault among inos (Lutinos, Whiteface Lutinos or Albinos) and Fallow color mutations? Consider now the fine details. For example, is the upper and lower mandible of correct shape? Have you spotted any crossed, “scissor” beaks, undershot or overgrown beaks, any of which can be genetic (if not caused by accidents) and difficult to work out of a line. Are the eyes round or almond shaped, lacking drooping eyelids, signs of bulging, or gaping lower conjunctiva? These undesirable traits can be inherited and as such are faults. Are the nares (nostrils) of correct size and position without deformity? Are the legs and feet strong and straight? Finally, examine the color mutation of each bird. The Standard calls for 5% for depth and uniformity in color, with the remaining 5% for degree and consistency of markings. This 10% is the “icing on the cake” only after you produce the rest of the qualities sought. The Top Birds Emerge Take the final bird(s), or group of birds that have not been eliminated; these are your top birds. You can use these birds to help further your line, or if they are good enough, create a line or build additional lines. It all depends upon your breeding goals. The remaining birds are your “culls,” and may be sold to other breeders or used in separate lines to produce pet stock, providing they are all healthy, fertile and will not pass on undesirable genetic traits. The latter must be qualified; although it is by no means necessary to set show qualities in the production of pet stock, it is necessary to avoid passing along any genetic flaws, or traits, that would negatively impact the health or reproductive abilities of future generations of any cockatiels, show stock or otherwise. Foundation Stock If none of the birds are of sufficient quality to begin your line and your goal is to establish your own cockatiel stud, then securing the best foundation stock that you can afford and starting with fewer birds that are of superior quality, is the way to go. It is senseless to breed a larger number of lesser quality birds, especially if you are breeding for show. Even breeders of champion lines usually have extra stock for sale, which is often superior to the best stock made available by less accomplished breeders. Choose someone with a reliable reputation for consistently selling good stock that reproduces high quality birds and buy fewer birds for a higher price as a future investment. Most reputable breeders will not take advantage of a novice or those wishing to begin breeding for show, and will want to get them off to a good start if for no other reason than for positive word of mouth advertising or repeat business. (That is, if they value their reputation). They will be the one’s to stand behind their reputation to make certain you are satisfied. Remember the adage, “like produces like.” One cannot breed quality if it is not there to begin with. Quality must be present in order to produce better birds. Even if the aviculturist is not breeding for exhibition, the same objective is shared; that is, to produce large, healthy, viable young. The goal of any breeding is to eliminate detrimental faults while maintaining positive traits in both the genotype (the full genetic “makeup” including species survival traits such as innate parenting skills and effective fertility), and the phenotype (the outward physical appearance). ”Like produces like,” can similarly, be applied to passing on detrimental faults such as a droopy lower eye-lid, or a bald spot in the phenotype, as easily as it is to pass on a desirable trait. Outcrosses When attempting to improve existing stock and bloodlines, it is best to bring in an unrelated outcross that exhibits the superior traits you are seeking to infuse into your stud. For example, if you determine that your lines lack thick full showy crests, large round cheek patches, or deeper facial masks, then you must secure birds that outwardly exhibit and reproduce these traits in all their offspring. The key to successfully using an effective outcross is to secure the bird from stock that is also linebred, so that it has the necessary qualities already set as dominant traits in its line. These qualities will then be evident in future offspring when birds are correctly paired. Deterioration of the Stock Another appropriate time to introduce an outcross is when breeding stock or bloodlines show symptoms of degradation or deterioration. Phenotypic examples might include chicks that diminish in overall size, lack crest density or good wing carriage. More serious genotypic examples include frequently producing chicks with weakened immune systems, failure to thrive, early liver disease or cancers; or when parenting skills decline so that pairs quit sitting eggs full term or feeding chicks through weaning. Cockatiels that have each clutch of young repeatedly pulled and are never allowed to finish feeding out their own offspring may eventually lose the ability to do so. Unfortunately, if the cycle continues, future offspring and subsequent generations may become affected by losing the traits that provide effective parenting instincts. Aviculturist become trapped in a cycle of forced handfeeding when parent birds quit sitting full term, or abandon their young before fully weaned. To prevent this, aviculturists can allow pairs to feed out at least one full clutch at the end of the breeding season. Another genotypic trait to watch is fertility. Fertility must never be sacrificed at the expense of other traits. Healthy cockatiels must maintain the instinct and ability to reproduce in order to survive. Pairs that produce only one to three eggs in each clutch are showing signs of reduction in fertility. It is not only necessary to pair such birds to vigorous partners; it is necessary to follow and record the quantity of eggs produced from these birds so that better producers are selected for to continue viable bloodlines. This selection will enable the genotypic trait of fertility to be set in a failing line. If breeding for show, some obvious outward signs of stock deterioration may include a lack in |
