Unsure about the cause of "notches" missing from tail feathers...

[Ghosty]

Stress Bars
Feather growth requires a myriad of nutrients for normal feather development. Therefore, if there is disruption in the assimilation of nutrients during the time of feather development, this will result in the production of stress bars on the feathers. Stress bars appear as black or depigmented lines that transect a feather, and multiple lines may occur at different levels on the feathers, if multiple bouts of disruption have occurred. If a young bird develops gastro-intestinal problems, digestive disturbances, prolonged chilling or periods when it is not fed (nor fed enough), this will result in the production of stress bars at the same level on all the feathers that were developing during that time.

It may well be feather mites. They live on the chicken and you should be able to see them if you look carefully.
If not, the above can cause similar.

Quill mites are microscopic and live most of their lives inside the shaft of the feather. They can't be seen.

 

[Shadrach]

Quill mites are microscopic and live most of their lives inside the shaft of the feather. They can't be seen.

Oh okay then.
I suggest the OP has a look anyway. Try with a magnifying glass. Feather mites are relatives of the red mite afaik. I must have seen something else then.

 

[Ghosty]

Oh okay then.
I suggest the OP has a look anyway. Try with a magnifying glass. Feather mites are relatives of the red mite afaik. I must have seen something else then.

Definitely worth a try. I'm just quoting what I read, no offense. May have to take a sample in to get it examined.

 

[Shadrach]

Definitely worth a try. I'm just quoting what I read, no offense. May have to take a sample in to get it examined.

No offense taken. I'm not exactly a feather mite expert having only seen the problem once and even then not been absolutely certain about what I was looking at.

 

[rozzzatar]

Stress Bars
Feather growth requires a myriad of nutrients for normal feather development. Therefore, if there is disruption in the assimilation of nutrients during the time of feather development, this will result in the production of stress bars on the feathers. Stress bars appear as black or depigmented lines that transect a feather, and multiple lines may occur at different levels on the feathers, if multiple bouts of disruption have occurred. If a young bird develops gastro-intestinal problems, digestive disturbances, prolonged chilling or periods when it is not fed (nor fed enough), this will result in the production of stress bars at the same level on all the feathers that were developing during that time.

It may well be feather mites. They live on the chicken and you should be able to see them if you look carefully.
If not, the above can cause similar.

They have access to unlimited amounts of Purina Start & Grow. The only time they don't have it is between 7:30PM and 6:30AM. I pull it out of their area at night and put it back out in the morning. They also have access to grass and bugs when their run is open during the day and variety of leftover veggies/fruit from the house a number of times throughout the week.

 

[rozzzatar]

I have seen feathers cut right on the shaft creating a V shape. Never seen the side part looking like a scissor cut.

The issue with mine turned out to be mice during the night. I caught them in the act. They had quite a nest in a wall cavity.

I thought mice as well maybe! Put mint and other repellent herbs in the coop and around the night run as well once this started. Having their feed hanging helps keep the food waste on the ground to a minimum plus pulling it each night too.

 

[rozzzatar]

This is their space right now. Working on building their permanent day run. The red and white "barn" is their night time coop/run and the new wood structure is their day run with a moveable fence portion that I move around every other day. At night they're in the red/white portion which has 1/4 inch hardware cloth walls and a 1/4 hardware cloth skirt running 6 inches into the ground and 12 inches away from the structure.

 

[aart]

Here's some info on depluming mites:
https://www.backyardchickens.com/th...es-nothing-works.1256486/page-3#post-20162786

 

[Trux]

Here's some info on depluming mites:
https://www.backyardchickens.com/th...es-nothing-works.1256486/page-3#post-20162786

That was my thought as well aart. Remember the post of the person who posted microscope pictures of a mite in the poop smear. You won't see deplumbing mites with a magnifying glass, they live inside the feather shafts

 

[Goatcrazychickengirl]

What do you feed your chickens?

Could this be a parasite? I've never hear of one eating feathers...