I cannot see the video for some reason. How long has this been going on? Did it happen right after eating some feed? Do you see any watery/bubbly eyes, sneezing, or nasal drainage? Stridor is a sound they can make when a small piece of feed gets stuck in the airway. Here is a video in post 1 of a chicken having stridor, which usually goes away in a few hours, unless they are having respiratory disease symptoms: https://www.backyardchickens.com/threads/silkie-w-possible-stridor.1218528/