What are Stress Bars on Bird Feathers?

Stress bars are lines that run horizontally across the width of a feather, and appear as the feather is growing.

They are most commonly seen on tail feathers and can be caused by a variety of reasons including:

– Nutritional deficiencies
– A stressful experience
– Trauma to the feather as it’s growing
– Illness

All of these reasons would need to coincide with the feather growing in order to be present as stress bars.

Stress bars won’t go away until the next moult, so even if the reason for the stress bars appearing is resolved, they will still be present until the feathers fall out naturally.

The photo shows one of Louis’ tail feathers that finally moulted out which contains multiple stress bars, and we know exactly why this happened!

When Lou and Kip first came home to us, Kip was quite excitable and erratic, and would climb all over Louis to get to where he wanted to be. This often meant stepping on his tail. As Louis was growing in new tail feathers at the time, this one clearly took a bit of a beating and caused a few stress bars to appear! None of his other tail feathers have this, and We are glad he has finally moulted this one out!