Twin HatchesCockatiel eggs are various sizes and weights. Sometimes mutations have something to do with size, or it is inherited, how long it takes to travel through the oviduct. Shapes vary from totally round to very oblong. The average egg weight is 5-6 grams. The 1st. Illustration shows several egg sizes with weights with notes as to the abnormal appearing eggs.
I am going to focus on the larger egg, which in many cases can contribute to a double yolk and a twin hatch.
I learned many years ago that even writing down and counting the eggs in the nest can result in more chicks than expected. This happened a couple of times before I realized what was going on. There would be 4 eggs, yet when I checked a few days later after hatches there would be 5 babies. What?…When did I move an egg or baby around? Did I count wrong? There are no eggs or babies missing in other boxes. What is going on? When I first started breeding I made up nest box cards to write down info in regards to when an egg was laid, hatched, fostered, etc. as a means of keeping track of things.
Then I started to really look at the variances in egg size. I noticed mutations like my recessive silvers and fallows had smaller, rounder eggs. Some hens consistently had oblong eggs, many first timers would have a tiny egg, and some of my pied lines I was breeding for splits to other mutations were laying very large eggs. Out of curiosity I started to weigh the eggs. Since I had learned that certain times of the years I was having a lot of DIS (dead in shell eggs) I started candling eggs, and used candling as a guide on development and monitoring close to hatch. In doing this the mystery was solved as to the extra babies. In candling it appeared that there was more yolk than there should have been in the larger eggs. I broke open a couple that were infertile and noticed that there were 2 yolks. On other large eggs the yolk was oversized compared to a normal yolk from a normal sized egg. I also made it a common practice to also break open any egg that was DIS or did not hatch to use as a learning tool on why they did not hatch. In doing so I discovered that in the larger eggs that had the oversized yolk there were two dead chicks, sharing the same yolk. And the double yolked eggs had 2 chicks that developed independent with each other because they were not sharing yolk and blood supply which greatly increased their chances of successfully hatching. The second pix shows a DIS twin hatch with a shared yolk.
The third pix shows two pieds from a successful twin hatch. The mother of these babies was an older sister of the hen that had the DIS twin egg.
I have the daughter, Thomasina, of the pied hen that has had both live and DIS twin eggs. She has been breeding for several years and has always had normal appearing eggs, good hatch rate and her and her mate, #4 (ran out of names) excellent parents. Thomasina and #4 have had one clutch this year, and are weaning out a baby and had started their second clutch. We have been having a lot of erratic weather that can affect hatches. Extreme changes in temperatures can disorient the pipping eggs, and many times have an erratic pip and hatch out the side of the egg. We have went from a very dry winter and spring to our rainy season and excessive humidity. The excessive humidity is problematic because in addition to the parents wetting the egg, the egg is porous and can draw in additional moisture from the air. When this happens the air cell starts to reduce in size. When this happens there is a great risk of the chick swelling from the excess moisture and smothering or drowning from the excess fluid in the egg. This time around Thomasina had very large eggs. I had also fostered a couple of eggs I had in the incubator under the pair that were approx. the same stage of development. While candling the eggs I noticed the air cell size was getting smaller with Thomasina’s eggs. I though: ‘Oh crap, humidity’ Then I noticed that they had tried to open the egg. I pulled the egg and put in an incubator. From the bit of chick that was exposed it looked very swollen, and wound up dying, so I took it out of the egg (pix 4 &5) and noticed the yolk was partially congealed. I had never seen that before and the only thing I could think of is excessive heat because it has been getting almost 100 degrees during the day, in addition to 100% humidity. The pairs are setup in a shaded screened in porch, but the air temp is hot. I have eggs actually hatch on their own without being incubated because of the heat. The pairs would just go in to turn the eggs. I try to have my breeding season done before summer, but it has been warmer than usual this year, and we have had no winter to speak of.
Back to Thomasina and #4. In candling some more of her eggs that I was monitoring the air cells they appeared to have become DIS. I opened up the one in the 6th pix and was puzzled by the contents. I couldn’t get a close enough shot to bring out detail but it appears that cause of death may have been by an early death of an additional embryo. Hmmmm…then I started to go back in her records and noticed that Thomasina was the daughter of a hen that produced double yolked and twin eggs, like the ones in the 2nd pix.
Years ago when I first realized that I was having some occassional twin hatches I confided in my vet and showed pix’s when he came over for a flock visit and evaluation. He had insisted that the chicks would be identical, and I showed him pix’s and some live hatches and none were ever identical, only fraternal twins. Most times it was 2 different mutations in the same egg. For instance, in pix 2 there was a fallow baby and a dark eyed yellow down baby. The mother of that pix was also a twin hatch…she was a normal pied, and her twin was a cinnamon pearl pied. The last live twin hatch I had contained (once feathered) a normal grey and a WF emerald. I have also learned that the only way there can be a live hatch is if there are 2 yolks. When there is 1 yolk the embryos are sharing the yolk. As they develop they are on either side of the yolk, and as they get close to piping, if not in sequence and positioned right one will weaken and die, which can cause the death of the other chick. Assist hatching is very risky because it is hard to tell where the babies are exactly, and which one to actively assist. With a double yolk the babies have a little more freedom in movement independent from each other as they get close to hatching and start to pip. Many times their pip marks are on opposite sides of the circumference of the eggs, and they pip in tandem to get out.
Sorry for the long posting. Has anyone else ever had suspected twin hatches or some strange eggs and hatches?
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