Rumpless: Blue egg layers with no tails

[Meadowlark Ranch]

For Araucana breeders who have rumpless birds: I have a flock of Whiting's True Blues that are 3 generations down from Murray McMurray Hatchery birds. All of the original hatchery birds had tails, some of the F1s had tails with no bones, and this year, I have about 3 of 16 birds with no tail at all. There are no bones or fatty tail structures past the pelvis.

The 3 chicks all had trouble hatching but all are healthy. They aren't as big as their siblings at 3 months (photo of one of the hens with her brothers) and their rear ends are a little messy as they can't lift their tail when eliminating. So I have questions:

1. Are there any concerns with adding them back to the flock mix or selling as blue egg layers? I don't want to pass on problems either way.

2. Is this genetic condition called rumpless and what is the heritability? Any articles?

 

[Meadowlark Ranch]

I did just find this posted on another thread:
https://www.sciencedirect.com/science/article/pii/S0032579119429684

I must have "accidental rumplessness" as the parents of all 3 birds have tails? Or an intermediate form that isn't the dominant Rp?