I would like to hear the reason sail feathers on Eider HENS do not stand up as often as that as on a drake. Is it a breading thing, mood/ behavior change, or is that they really do not stand up at all ?
the feathers that you are referring to are known as "sails" or "thorns", and are actually "post humeral" feathers. Their placement is located after or "post" scapular group at the rear or posterial feather tracts or "pterylea" of the scapulars. These feathers (aka sub-scapulars) are stiffer feathers that support the entire scapular feather group in flight, diving, etc. They are also used for courtship displays in the eider species (genus Somateria). The female has smaller and shorter "thorns" and although they are usually covered by the scapulars, they are often visible.