Pigeon health

   Egg retention

WARNING! This article — and its photographs — is about the autopsy of a pigeon. If you have concerns about reading such text and viewing such images, please do not read this article.


I came across an extraordinary case some years ago. A mondain breeder called me because one of his hens was unable to lay the egg that was palpable just before the cloaca.
He tried to lubricate the cloaca by administering some paraffin oil on it, but this did not help. (In most instances it does not help.) The hen was a valuable breeder, so he wanted to know if a surgical solution was an option. Unfortunately, I was out of town and did not expect to get back before late at night. So the breeder took the hen to a colleague and I would see him in my surgery the following day.
The client decided to have his bird x-rayed in my colleague’s surgery. The film, however, did not give a good diagnostic hint – we will see later why. It was not clear if the egg was present on the film at all because the object did not give such contrast as a calcified organ – like bone or fully developed eggshell – would be expected to. Finally, the owner did not accept the risk and the cost of an operation, and the bird was put down.
The following day he brought the bird in to my surgery for an autopsy. The external examination revealed a well-palpable object ahead of the vent that was larger than an average mondain egg. However, it felt dense and elastic, resembling a tumor much more than an egg.

Click onto the photos
As I opened the abdomen, it turned out that the object was located in the lower part of the oviduct.
So, it must indeed have been an egg. When I cut through the uterine wall, a really large egg became visible which have no calcified shell at all.
That was the reason why it did not produce a visible contrast on the x-ray film. Beyond the first egg, I found an even larger second one in the oviduct.
This egg did not even show the regular egg shape like the first one; its longer axis was strangely bent. Its shell, like that of the first egg, was not calcified either.
When I took the first, smaller egg and cut it in half, another surprise occurred; the inner part of the egg did not show the classic picture at all: it did not contain liquid white and yolk. Instead, it was filled with a layered, elastically dense material.
Oddly, it seemed like the embryo had already started to develop inside the body of the hen. Then I took the second, larger egg and carefully cut it in half, exactly through the longer axis – and what I found was a shocking experience. In this second large egg we found an almost completely developed chick.
The picture clearly shows a partially absorbed yolk around which is a typically positioned embryo. Its head, the cranium, even the shape of the beak are clearly visible, as well as the backbone and the whole body. Even the impression of the umbilical chord that connects the embryo to the yolk is visible. Trying to find an explanation for this unusual case, I resumed the dissection and probably found the cause as well. On the sternum of the bird were signs of severe previous injuries.

Photos: Szabolcs Kürtösi, Hungary
This indicated that the bird had lately had an accident; maybe it had fallen down on the ground or hit a sharp, solid object. It is conceivable that the accident caused injury in the oviduct as well, rendering it incapable of building a calcified shell around the first egg and of passing it on. Then the second egg developed, which became even larger than the first one, and was wedged in the oviduct behind the first egg. The two eggs could not get out of the bird’s body, but they did not kill the pigeon. This is why there was enough time for them to start developing inside the pigeon’s body. Getting philosophical and thinking this case further, we can easily end up with interesting assumptions. If, by chance, the hen would finally have been able to lay the eggs and the chicks would have been healthy, they should have hatched long before the end of the normal incubation period, giving the breeder a hard time to figure out what happened. Furthermore, what a surprise it would have been had the hen given birth to one or two live chicks!
Wow… This really sounds like science fiction, but there really are examples like this in evolution. Indeed, we can find viviparous species in addition to mammals at earlier stages of the evolution. Examples of such a creature are sharks or vipers; the latter earned its name after this fact (viviparous in Latin: vivi para as vipera or viper). It seems that the possibility of possibilities is given to other species as well... Is what just happened during the autopsy of an unlucky mondain hen an insight into the deepest secrets of evolution? Whatever it is, if you look at the picture for a long time, a strange feeling starts to embrace you…
 
 
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