hunched back

Hi, what can it mean if a pigeon goes into these phases where he sits slightly hunched with his head stretched and low, level with his back? Thankyou

(Video Uploaded)Wings falling toward the side ,hunched back,head downwards. Hi everyone, Hope you all are doing good with your birds.I have a fantail female that has wings falling toward the side ,hunched back,head downwards and calcium deficiency.She is eating and drinking properly.She is...