Conjoined Barn Swallows

[KCFoggin]

This is a bit startling:

http://www.boston.com/news/odd/articles/2008/07/19/conjoined_barn_swallows_cause_stir_in_arkansas/

and from Associated Press:

http://ap.google.com/article/ALeqM5idTxQ25-aE9USdHcXJ26y_HJpZcwD920H7981

[dantheman]

Never heard of that in birds before. Although I've heard that Double yolkers in chicken eggs always were desirable and not that uncommon before factory farming. Wonder if any of them could have ended up conjoined if allowed to hatch?


(And I wonder if the 'humorous' opening line in the AP article is meant to also be doubly humorous - considering the presidential location of the swallows . . . )

[Lisa W]

Very interesting thanks for sharing this one, KC.

[KnockerNorton]

I'm rather cynical that these are conjoined, although I'll await further info.

It is hard to imagine 2 embryos surviving to hatch from the same egg. Let alone be conjoined. There would not be enough room in an egg for 2 to fully develop to the point of hatching. Also, to be conjoined at the hip would be very strange - conjoined animals are usually not joined at the extremities, it is usually from the trunk/midline. It seems much more plausible to me that these 2 young have become attached in the nest, and have 'knitted together' somehow through adhesion. Especially as the x-ray showed there were fully formed - the article even says that they were attached at the skin and 'possibly the muscle', and that they were otherwise fully formed. Conjoining does not generally produce 2 fully formed animals.

[Farnboro John]

I somehow doubt that they would have needed teaching to fly once separated. Its never struck me that small birds get flying lessons from their parents.

John

[gambirder]

Don't get your response knocker. Are you saying there's fabrication involved?

It might be worth noting that human conjoined twins can be joined at the hip, chest, cranium . . . apparently just about anywhere. Yeah, I know, the relation between human and swallow is not that close . . . but surely the comparison hints at the awesomely vast scope of possibilities in the animal kingdom? I can certainly imagine two embryos growing and developing together in the egg, maturing and being ready to break out of the egg at the same time. Why not?

[KnockerNorton]

Don't get your response knocker. Are you saying there's fabrication involved?

No, I'm saying that they're not conjoined, just stuck together by accident in the nest. I'd put money on one bird adhering to the next through a skin lesion (constant abrasion) or getting damp or something.

It might be worth noting that human conjoined twins can be joined at the hip, chest, cranium . . . apparently just about anywhere.

yes, but that involves bone and organs, doesn't it. Not just the skin (and only possibly muscle). have you ever heard of conjoined twins joined at only the skin?

I can certainly imagine two embryos growing and developing together in the egg, maturing and being ready to break out of the egg at the same time. Why not?

because for an egg to produce one embryo results in that embryo taking up the entire egg and being squeezed in so tight that it looks like this http://www.dkimages.com/discover/previews/887/45066269.JPG . Try and fit another chick in that! For 2 to be in there, they could never get to 'full term'. So it would either have to be a double-sized egg (and how would that come about, seeing as the embryo was only a few cells in size when laid? it would have to predict the size of the future embryos. Let alone the issue of passing such an egg) or the embryos did not develop fully before hatching, which is also a no-brainer, as they wouldn't then have the strength/capacity to hatch or survive.