I take changes in their voices very seriously because it can be a sign of a respiratory disease or throat infection.I will try and either record a video or find a video of a duck making the same sound. I read somewhere that it could be a mould infection in her lungs, but their pond is cleaned daily and their cages are kept clean also.
Hens go broody when you don’t want them to… and won’t go broody when you do. 
