What Are Feather Stress Bars?
Ron Hines DVM PhD
During the period that a feather is forming, the follicle that produces the feather relies on a steady stream of nutrients (the amino acids needed to build feather β-keratin protein [ref]) obtained from the bird’s blood stream. If that steady flow of nutrients is interrupted, either by a lack of food or an disinclination to eat, the feather will no longer develop normally because the bird can no longer produce the keratin proteins that form the feather. When those nutrients again reach the proper level in the blood stream, feather development returns to normal. So a careful examination of a bird’s feathers gives you a look back into its past. In this particular dove, I apparently missed a scheduled feeding while the feather I am pointing to was developing. That resulted in the narrow white line – like a scissor cut present to the right of my finger. You can see that even the integrity and strength of of the feather shaft was compromised at that point. With time, that feather will break at both points. You can read a bit more about the problem and feathers in general here.
When a bird’s blood level of amino acids drops too low due to a lack of constant food protein, disease or environmental stress, a weak imperfectly-formed band will form in the developing feather (“blood feather”) that will not become apparent until the feather has fully unfurled. When these bars occur in a bird you are hand feeding, the usual cause is not feeding frequently enough during the day. Feeding a diet that is too low in balanced amino acids or a bacterial or viral problem can have similar effects.