October 2001 Magazine
You have made the decision to breed your cockatiels. You understand that breeding pairs that are too young can cause problems because the parent bird is still using her body's calcium supply for growing bones and other metabolic processes. The inbreeding of related pairs cause heartache, needless suffering and gross deformities in offspring. Breeding birds that are in poor health is risky because of the problems with egg binding, peritonitis, and cloacal prolapse. Sick hens can transmit bacterial or viral agents while the egg is still in the uterus.
Now that your tiels have been examined by an avian vet and are in excellent health, they should reproduce healthy chicks. Incubation of cockatiel eggs is a wonderous, awesome event that takes place and yields tiny little fuzz balls which grow into beautiful healthy cockatiels. The very best incubator available is that of the hen's body.
The cockatiel is an opportunistic breeder. One of the triggers that will cause a pair to go to nest is an increase in the amount of daylight hours. Since we live in synthetic environments in our homes, we have daylight even when it is pitch black outside. These increased daylight hours provide the right trigger for getting your tiels to breed in January. Another important trigger is the nestbox. Research has shown that the parent birds have an increase in the sexual hormones that stimulate them to go to nest. So often just the presence of the nestbox will stimulate the pair and they will begin nesting activities. An abundance of soft fresh foods and daily showers stimulate breeding in a bonded pair of cockatiels. The cockatiel is an opportunistic and prolific breeder. When in captivity, if the tiel has the right stimulus, it will have no problems going to nest.
THE COCKATIEL HEN
A cockatiel hen will usually lay a clutch of four to six eggs. She lays an egg every other day until the entire clutch is laid. Most tiel hens do not start incubating once the first egg is laid. Some may start sitting after the second egg, but many will wait till the entire clutch of eggs have been laid before starting the incubation process.
The hen should be monitored while she is laying eggs. The key sign that a tiel hen is going to lay is that she will have an enormous dropping which is usually a shock to the first time breeder. This signifies that the hen will be laying an egg in about twenty-four hours. Eggs laid should be candled to make sure that there is a yolk in the shell. Sometimes the yolk doesn't make it into the hen's reproductive tract and falls into her abdomen. This can result in egg yolk peritonitis which is a serious infection that must be treated by an avian vet immediately.
Eggs are incubated by the pair for 18-21 days. As the time approaches for the eggs to hatch, my pairs will divide the eggs between them and sit together as they anticipate their chicks hatching. During this time the male will feed his hen and guard their nest from predators. When the eggs are ready to hatch the pair will bury an egg to allow a time for the egg to cool down. This is very important and causes a change in the gas exchange in the egg, increasing the amount of carbon dioxide within the egg and signaling the chick that it is time for the internal pip into the air cell.
With inexperienced breeders you may have some spats between the parent birds as they sort out who does what job in the incubation process. Rarely is there violent aggression between the two birds. However when this does happen, it is important to remove the male bird, as he may seriously hurt or kill the hen. Not all cockatiel pairs make good breeders and there are some cockatiels who should never be allowed to breed. It is better to allow them to remain pets.
DIET ALWAYS A CRITICAL FACTOR
The diet of the cockatiel hen is vital to successful breeding since everything the embryo will need to sustain life and develop must be contained in that egg before it is laid. Feeding a varied, nutritious diet plays a significant role in the health of the embryo as it is developing in the egg. Calcium, Vitamin D3, and phosphorus are important to the diet of the breeding hen. Without these essential elements in the diet, the hen's bones are depleted of the stores of calcium in her as her body tries to maintain its normal blood calcium level.
Fertilization takes place when the sperm cells enter the yolk after traveling the length of the hen's female reproductive tract. There is approximately a fifteen to twenty minute window when fertilization of the yolk is possible. This must take place before the first layer of albumin is laid down on the yolk. The nutrients in the egg are what sustains the embryo while it is developing. The importance of calcium is mentioned frequently so that the hen's body isn't drained of the necessary resources. It needs to be mentioned that the embryo receives calcium from the egg. An inadequate supply of calcium to the embryo can result in rickets, splayed legs, or even the death of the chick. The formation of the egg shell is dependent upon enough calcium being drawn from the hen's body to form the shell layers of calcium carbonate.
In the process of incubation, cockatiels share the duties of sitting on the eggs. Most often the male tiel will sit on the eggs during the day while the hen sits during the night. Males will guard the entrance to the nestbox to protect the hen and his eggs from any predators. It is normal during this time for the male cockatiel to be aggressive if anyone comes near the nest. My own males will give me what I call "the beak of death" which is a warning that I should not come too close. I find that the male parent is gentle and tender towards his hen and his chicks and quite protective of his family. The parent birds will turn their eggs many times a day. This is extremely important to the vascular development of the embryo. The turning also prvents the yolk from laying in the same spot for a long length of time, ensuring that the chick will be in the right position for hatch.
Heat causes the embryo to start developing. When the heat is too high or too low, the chick dies before it has an opportunity to hatch. The higher the heat, the quicker the development of the embryo. The best possible scenario is for the embryo to develop in the same time frame of that of the parent birds. Cold temperatures or a chilled egg almost always results in the death of the embryo in the critical first two weeks of incubation. One of the problems encountered with inexperienced or immature hens is that they will come off the eggs at a critical time in the incubation of the eggs, allowing them to become cold or chilled. When this happens in the first two weeks, the embryos stop developing and this results in dead in the shell chicks. The hen will come off the eggs to eat and take care of her needs. The eggs that are left in the nest, being in close proximity to each other, will remain warm for short periods of time. It is when the hen abandons the eggs for hours at a time that there is cause for concern. After the first two weeks variations in temperatures seem to have less negative effects on developing embryos.
The humidity regulates the amount of moisture that is able to escape through the pores of the egg. During the incubation process, the egg loses weight due to the loss of water during the time of incubation. When the humidity is too high the chick takes on extra fluids in his body resulting in a water logged chick. As a consequence the chick may drown in the excess fluid because it has no air cell from which to breathe oxygen. With a higher humidity you will also notice a smaller air sac and the chick will do an external pip below the air sac. This means that his critical need for breathing oxygen at this time is not taking place.
Humidity that is too low causes the chick to adhere to the inner shell membrane and makes it virtually impossible for the chick to hatch without assistance. It is possible to have a chick hatch that is dehydrated because of inadequate humidity. It is then very important that the chick be given fluids and placed back in the nest box with an increase in the humidity. The cockatiel hen will daily bathe her breast feathers in order to provide her eggs with the necessary humidity. A flat shallow dish of water needs to be provided in the cage for her to bathe in everyday. I've found that in the Northeast that homes are heated and are too dry for birds that are breeding inside. To alleviate that circumstance, I add a small amount of salt into the nesting substrate. The salt draws moisture into the box and increases the humidity. Since starting this practice I haven't had any problems with chicks hatching normally.
Once incubation is complete and the chick is starting to hatch there is now a greater need for a higher humidity level. The higher humidity will make it less likely for the chick to stick to the membrane of the egg. Since the incubation of the eggs is complete, there is no need to worry about the transpiration of water from the egg because at this time the chick has pipped in the air cell and is breathing oxygen on its own. Overly dry membranes will cause a chick to have problems with hatching. Malpositioned embryos will have problems with their heads not in the right position to externally pip the egg. When the humidity has been too high the air cell is very small and the chick's internal pip will often be below the air cell. The chick's need for oxygen is critical at this point and because the internal pip is not into the air cell the chick becomes disoriented in the egg and turns so it is malpositioned and its head is in the narrow part of the egg away from the all important air cell. This results in a chick who dies while trying to complete the hatch.
One of the signs that the egg is getting ready to hatch is that the air cell at the wide end of the egg will begin to slide off to one side of the egg. This is know as draw down and happens just before the chick begins to hatch. The amount of time between draw down and the chick hatching is anywhere from 48-72 hours. The chick's internal pip is into the air cell where it will take its first breath of air. It is at this time, when the chick is starting to breathe oxygen for the first time, that you may hear the chick peeping inside the egg as it is getting ready to hatch. Before the internal pip into the air cell, the chick received oxygen and exhaled carbon dioxide through the pores of the egg shell. In draw down you see the air cell enlarging at the wide end of the egg. An external pip looks like a small dent on the outside of the egg. And this is a sign that the hatch is progressing. It can take up to 72 hours for the chick to complete the hatch. One of the things that is extremely important is that there is adequate humidity so that the chick doesn't stick to the membranes of the egg while it is trying to hatch.
DEAD IN THE SHELL CHICKS
There are several major reasons why this can occur. Malnutrition of the parents is a contributing factor. Deficiencies of vitamin E and Selenium cause reproductive problems in breeding birds. Excessive humidity during the incubation process causes problems with transpiration through the pores of the egg shell. The gas exchanges take place through the pores of the egg before the internal pip of the chick into the air cell. A high humidity can cause the chick to attempt to hatch from the wrong end of the egg. The right relative humidity is therefore extremely important to having chicks hatch successfully.
Incubation of cockatiel eggs is as you can see a very complicated subject. Successful breeding and hatching of chicks is dependent on many different factors. Healthy parent birds, a nutritious diet, the right amount of heat. One important thing to remember is that your cockatiel hen can't overheat her eggs. The turning of the eggs is so important for the vascular development of the embryo and for correct positioning in the egg for hatch. Humidity is a critical factor and must be checked regularly. The age and experience of the cockatiel must be considered, as problems are likely to be encountered if she is too young or inexperienced. I hope this article has given you a better understanding of the incubation process. Until next month, when I will continue this series on the responsible breeding of cockatiels.
Winged Wisdom Note: Iris, Bob, and their three children live in Maryland. They are owned by 19 birds. The flock consists of a bare eyed cockatoo, a Congo African grey, a quaker, a senegal, a green rump parrotlet, a lori and 12 cockatiels.
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