Bantam Langshan with Intermittent White Tipped Feathers

[Teila]

Howdy folks

What causes the tips of black chickens' feathers to go white?

This is a picture of Dusty [Bantam Langshan] in August 2014, the white bits are obvious [she moulted in April that year]:



Since that picture she has been all black at times and white tips at others. I noticed yesterday that she has white creeping back in again.

I have not managed to pin point a time-frame, for example pre moult or post moult, but I have noticed that in her three and a half years, sometimes she is all black and others, black with white tips.

I have a Bantam Cochin [aka Pekin here in Aus] and she is black and always been black, no intermittent white on her.

 

[Teila]

Just thought that I would add that I was asking out of curiosity only. As this has been going on for years and besides a couple of crop issues being related to 'Eyes bigger than belly' syndrome

, I am not concerned about her health as Dusty seems to be pretty healthy. No mites, lice or worms either.

I thought it could be environmental but I have no idea what and if it was, you would think it would affect my other black chicken. They have lived together in the same accommodation for over 3 years now.

I mainly asked in case others have seen this and may know the cause?