Tuesday, July 1, 2008

Photo Essay - From Hatching to Fledgling

Looking at this photo I wonder at the marvel of creation and how compactly the developing chick is in the egg prior to hatching. It is a marvel as I know that the chick does not even occupy the entire egg. It sits in the narrow part of the egg during its development. The broad part is filled with air which has increased as the chick develops until, at the time of hatching, it occupies about 30% of the egg’s volume. This space is a reservoir for the air that the chick will need when it hatches. Prior to hatching, the embryo does not use the air in the space. Instead, the egg-shell is porous and gases are exchange through the shell. Stale air passes from the embryo to the outside and fresh air replaces it.

When the chick is about to hatch, it uses its egg-tooth to break through the membrane separating the air-space from the rest of the egg. The egg-tooth is a hard bit at the tip of the beak. It will fall off after the chick has hatched. After the chick chips a hole through the membrane, it is able to breath the air in the space. It then turns its entire body around so that it occupies the broad part of the egg instead of the narrow end.

After the chick performs this contortionist manoeuvre, it will squeeze its entire body into the broader part of the egg and it will occupy about 60% of the entire egg. It then uses its egg tooth to chip through the membrane that surrounds the egg shell and the egg shell itself until it makes a hole. It then turns its body ever so slightly and chips a little more of the egg and continues to do this until the almost the entire circumference of the egg has been chipped. The action is much like using a can-opener. The chick will rest in-between chips and it may take 2 hours or more to chip around the entire circumference of the egg.

During the time that the chick is working to emerge from the egg, the incubator lid should not be opened if the egg is being hatched in an incubator. To do so will result in cooler air entering the incubator and this could cause problems in hatching.

When almost the entire circumference of the egg has been chipped, the chick heaves its upper body upwards. It may take several heaves over many minutes but eventually the narrow part of the shell separates from the bottom and the chick emerges. The photo shows the chick after it has partially emerged from egg-shell. After it has rested, it will push its way out of the rest of the shell.

The parents, usually the hen, will remove the two pieces of egg-shell. They will take it in their beak and deposit it in a corner of the aviary. Sometimes, the egg-shell will be deposit "as is" or the parents will peck it into bits or perhaps even eat it. By taking a count of the egg-shells, an observer can have a good guess at the number of chicks that have hatched without tooking into the nest and stressing the parents.

You will see from the photo that 3 of the 5 eggs have hatched. The other 2 eggs are also fertile and will hatch a day or so later.

The embryo starts to develop when the temperature outside the egg is above 21 degrees centigrade (70 degrees fahrenheit). In the tropics where the daytime temperature is often above 30 degrees centigrade, it will be seen that the embryo will start to develop almost immediately the egg is laid. The embryo’s development will be faster if the outside temperature is warmer and it will slow down if cooler. The ideal temperature for hatching shama eggs is in the region of 37.4 degrees centigrade. If the temperature is much lower than this but above 21 degrees centigrade, the embryo will develop much too slowly and the chick will die prior to hatching.

What happened with the above eggs is that the hen commenced sitting after the third egg was laid but she only covered the eggs during the day. On the third night, she did not sit on the eggs but roosted on a perch. The following day, she laid the 4th egg, sat during the day and again roosted on a perch at night. She only commenced fully sitting on the eggs after the 5th egg was laid.

The result was that the first 3 eggs hatched more or less on the same day followed by the hatching of the 4th egg a day later and the 5th egg after that.

....... to be continued

These are Icon's chicks at less than 2 1/2 days old.

Last year, I took 12 chicks from the parents of which 6 were male. The males included Longbow, Fireworks and Max. The tail lengths of 3 of the males after the first molt from juvenile were 10 1/4", 11", 11 1/4" with the remaining 3 chicks having tails exceeding 13". All the chicks are worth having but Longbow, with 11 1/4" tails, arguably can compete with Pretty Boy as the bset male I have ever bred.

I repeated the mating this year. The parents are feeding the chicks. As all the 5 chicks are about the same size and look happy and well fed, it can be seen that the parents are doing a wonderful job.

The mother laid 6 eggs of which 5 hatched. The female will usually lay 3 to 4 eggs and commence to brood when the penultimate egg is laid. When this happens, the last egg will hatch a day later and the chick will have less chance of surviving.

After the 3rd egg the mother did not sit and I was already happy. I expected her to sit upon laying the 4th egg but she did not so I knew there would be a 5th egg. She entered the box on the 5th morning and I was sure there was another egg but again she did not sit. She only commenced to brood after laying the 6th egg. The result is that all the 5 eggs hatched within the same day.

The 11th day after the mother commenced brooding was last Sunday. I was home for most of the day. I counted 2 half eggshells in the morning and another 1/2 eggshell in the afternoon. These eggshells were from the broader part of the egg and tell that at least 3 chicks had hatched. There could be more as the parents may have eaten the eggshells of the other eggs so that no eggshell can be seen.

The parents were attentively going up to the box with food in their beaks so many times that I felt sure there were 4 or more chicks.

I was anxious to know if the chicks were OK so I checked this evening and found 5 chicks. I have successfully had 5 chicks from a nest before. One of these days perhaps I will get 6 chicks from 6 eggs.

I should note that I usually do not check the nest as to do so may upset the parents and result in them abandoning the chicks. However, this pair is used to me and they did not mind me quickly checking and returning the box after photographing the chicks.

Icon's chicks at 6 days

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