Conjoined twin Barn swallows, Hirundo rustica,
found July 17, 2008 in Searcy, Arkansas after they fell from their nest.
Image: Samuel Peebles (Daily Citizen, AP Photo).
Last week, a homeowner discovered a pair of young barn swallows that had fallen out of their nest after a sibling flew off to learn to forage from its parents. That’s a common event, but this particular pair of young birds were remarkable: they were joined at the hip — literally.
Conjoined twins — sometimes known as “siamese twins” — have been described in humans and other mammals as well as in reptiles, but not among birds that anyone recalls. This might be because conjoined twin birds die before anyone finds them.
“I can’t even say it’s one in a million — it’s probably more than that,” said Karen Rowe, an ornithologist with the Arkansas Game & Fish Commission. “There’s just very little to no records of such a thing.”
Unfortunately, the twin birds did not survive. By the time the person who discovered them had notified wildlife officials, the two birds had stopped eating. One bird died shortly thereafter, on Friday morning, and a veterinarian later euthanized the surviving twin.
The birds first appeared to have only three legs, but further examination found a fourth leg tucked up underneath the skin connecting the pair. Additionally, X-rays showed that the birds were fully formed, alhtough it is not clear if they are identical or fraternal twins. Their bodies are being sent to the Smithsonian to gain a better understanding of how these birds developed.
According to Rowe, the twins had to develop from a double-yolked egg. But even if they had survived, it would have been difficult to teach the birds to fly, added Rowe, who is a master of understatement.
Barn swallows are aerial hunters that capture and consume insects in midflight. They build construct familiar mud nests that they plaster to walls and often to support structures in barns, hence their name.