Ibisring

Reddening in some of our birds, it is currently a hotly debated topic with many aviculturists of ibises, flamingos, spoonbills and pelicans. On Ibisday 2007, we have already dealt with this topic extensively. We want to give you, on the basis of a number of articles, more information on this subject, in this way we give you the opportunity to become a critical judge on the usefulness of administering colours and the role they play.

This is the fourth part of this series of articles. These are the other parts:

• Part 1: Review of carotenoids
• Part 2: Dose administration carotenes
• Part 3: What does a wild red ibis eat, among other things to be red?
• Part 4: Red ibises in wild, the flying labo (current article)
• Part 5: Color additives in an aviary

We have tried to turn the scientific literature in a smoothly readable text. We think it is always nice when we get feedback on our articles, do not be afraid to state your experiences with us.

Part 4: Red ibises in wild, the flying labo

Introduction

Female birds can select a male partner on a large number of manners to pair. Thus they choose for example males with striking decorations, such as violent coloured and extended feathers. By choosing that splendid males, they are sure the descendants will be born healthy and vital. Because how better the males in condition is, how better their decorative expressie reach, therefore how better their genen. A correlation between these decorations and the condition and survival on the other side has been on the one hand shown already. When a bird will be in bad condition, this will reflect itself rather on its decorations then on other morphological properties. It is for a female therefore of very large importance to paire with beautiful males for this way descendants will obtain a good condition. Birds which are by an external reason less attractive although they are in top condition, will find less partners (Eeva et already. 1998, Olson & Owens 1998, Schantz et already. 1999). The reason why birds in bad condition produce less beautiful feathers, tracks, song or peaks; it is now discussed. This discussion will allow afterwards a critical view on the artificial colouring of ibises.

From free radical to antioxidant

In numerous biological processes (celrespiratie and - metabolism, biotransformation or demolition, immunity protection) free radicals are produced, who are molecules or atoms with single electron (= globule what floats around the core of the molecule). Such a configuration is energetically unfavourable and the radical will very rapidly want proceed to a paired structure by reacting for example endosperms, greases, cell membranes and even DNA. The end products which are formed, are detrimental substances for the body. Thus these radicals can damage for example the DNA seriously what leads to mutations which can influence the cell cycle negatively and even cancer to cause.

Oxygen (O2-) is an example of radical and because a lot of organisms are dependent on oxygen for breathing, is oxygen-based radicals very important in biology. The free radical will try electrons everywhere, it is as a matter of fact so reactive that they can take away an electron in a fraction of a second. Consequently there is another molecule that has an electron too a little what a collar response will start. A half-measure for the quantity radicals is oxidatieve stress; how more radicals, how larger the oxidatieve stress (Schantz et already. 1999, Opdenakker 2006).

The collar response which radicals initiate, can be stopped by antioxidant because these can neutralise a free radical. It can happen in two manners: first there are the enzymatic antioxidanten such as katalase and superoxide dismutase (SOD): in cell much oxidatie takes place in the mitochondriën for supplies of energy and as a by-product much free radicals arise. THE SOD directly will convert these into waterstofperoxide, which is demolished for its part by katalase. Thus several types of enzymes make thousands of radicals harmless. If these enzymes did not satisfy, then there are still the nutritieve antioxidanten, which are taken by means of food. These substances have the property that they easily give an electron without becoming thereby himself unstable. One distinguishes the vitamins (vitamin A and E and provitamin A), minerals (selenium, chromium and zinc) and other oxidanten (carotenoïden, anthocyaniden, amino acids, etc.). In contrast to enzymatic antioxidanten, nutritieve antioxidanten can perform their functioning only one time (Schantz et already. 1999).

From antioxidant to red ibis

Now the question can be asked what has these free radicals and antioxidanten have to do with the colouring of birds. Carotenoïden are antioxidanten which are also responsible for the colouring of beak, egg or feathers of birds. These animals can apply carotenoïden as a pigment when their low oxidatieve have stress. At high oxidatieve stress (much free radicals) these carotenoïden are, as it happens, used to neutralise the free radicals, these carotenoïden loose their colour in that proces. Consequently there is less carotenoïden for the colouring of the decorations of the birds. An additional condition is that there ned to be sufficient carotenoïden in the feeding of the birds. Only plants can produce carotenoïden, therefore animals can only by means of feeding take these necessary carotenoïden (Olson & Owens 1998). An additional impact of carotenoïden is that they stimulate hormone production that has an impact on breeding (Olson 1998).

Therefore there can be concluded that a bird in top condition has a little free radicals and therefore low oxidatieve stress. Consequently there must be less antioxidanten, therefore also carotenoïden, be applied for the radicals to neutralise. For this reason the bird can apply more carotenoïden as a pigment. Healthy birds have therefore a more striking colour. This manner of colours prevents that weaker animals can reproduce themselves by very striking indicators as colour. Weaker animals are, as it happens, not able apply a surplus to carotenoïden to use as sexual indicator. This way Darwin unique principle of natural selection remains intact because weaker and therefore less beautiful males can only reproduce themselves with more difficulty. Indicators, caused by carotenoïden are for this reason also called condition-dependent indicators of quality. (Olson & Owens 1998, Schantz et already. 1999, Hartley 2004).

Critical view on redcolouring of birds

From the previous becomes clear that nature has designed a particular interesting mechanism. In free nature coloration has been only put aside for the bests (vital, healthy, parasiet-vrije, etc.) males. Healthy males use much less carotenoïden to detriment harmless substances. For this reason they can use these dyes entirely to get a beautiful colou. Females always choose the most beautiful males and nature has ensured that this is always healthiest. These birds ensure that their descendants will be very healthy.

Also in our volières females choose the most beautiful males from (if they live together in a group). But in their food as such many carotenoïden that also the less healthy males have much surplus to dye, so that also they can paint their feathers very beautiful rscarlet. Indeed, in some zoos or at private collections, all ibises aresuper red, caused by a too large amount of carotenoïden. On the other hand to you see sometimes at other collections really differing in colouring between several birds, here no excess to dye has been administered.

At breeders that give too much carotenoïden, all males both healthy and the less healthy look very beautiful scarlet. The females can see no more difference between healthy and less vital males. Even less healthy males can breed, whereas in nature they probably never would come to. We can in fact, however, conclude that if we handle birds that way, we ignore he natural selection. We as birdkeepers must handle consequently and very strict towards our birds. Birds in less good condition we, how difficult that will be for some, cannot use to breed. We are already able of getting a much larger number of babies than in wild ever will succeed. The consequences of this are that also less fitte birds will survive. My proposal is that everyone once what more often would play Darwin at its own birds.

Text: Koen Thijs
Header photo: Valerie

References

• Eeva T., Lehikoinen E., Rönkä M., 1998. Air pollution fades the plumage of the Great Tit. Functional Ecology 12, 607-612.
• Hartley R.C. & Kennedy M.W., 2004. Are carotenoids a red herring in sexual display? Trends in Ecology and Evolution. Vol. 19, nr. 7, 353-354.
• Hermkens E., 2001. Anti-oxidanten: belofte voor onsterfelijkheid. Mens en Wetenschap 6.
• Hill G.E. 1992. Proximate basis of variation in carotenoid pigmentation in male house finches. Auk 109, 1-12.
• Olson V.A., Owens I.P.F., 1998. Costly sexual signals: are carotenoids rare, risky or required? Tree vol. 13, nr. 12, 510-514.
• Opdenakker K., 2006. Oxidatieve stress als modulator in metaaltoxiciteit. Eindverhandeling in de biomedische wetenschappen aan de Universiteit van Hasselt.
• Schantz T., Bensch S., Grahn M., Hasselguist D., Wittzell H., 1999. Good genes, oxidative stress and condition-dependent sexual signals. The Royal Society 266: 1-12.