Thank you!!! I hope its 2. or 3. Great info!The Legbar long, long ago got it's lovely egg color from a Collonocas that was crossed with an unknown breed. The "Collonocas" laid blue eggs and were rumpless. This is the bird that later had ear tuffs breed into it and is now called the Araucana. So your bird is most likely missing it's tail for one of three reasons.
1. It was damaged during incubation and is a fluke.
2. It is expressing a recessive gene from the original Collonocas blood in the Legbar.
3. Someone at some point breed this strain of Legbars to an Araucana to improve egg color and again your Roo is expressing a recessive gene.
Hope that helps!