This family of rollers has some interesting traits, including grouse feathered legs like Loper!
I like that guy’s videos. Piano Tail is gorgeous! Looks like he is wearing a tuxedo!
That feather pluck looked intentional to me. Like he was looking at it, and pulled it.

Checked on my pigeons this morning. It was 16º F. One bird gave up the ghost. It looked liked it starved to death. I am thinking it may have ingested wood pellets that I have began to use for floor bedding. I will begin to investigate when I have more time.
Lack of food I assure you is not the problem.
Has anyone else had this sort of problem?
Bummer! Hope you find the cause. Did your temps drop drastically? Ours have been up and down, up and down. I always worry more about the birds on this weather roller coaster.