Right photo – The (or a) “mantle” refers to the feathers in the upper middle of the back that form a “V” shape below the neck feathers (the nape) on the back of the head. Bird guides such as The Sibley Guide to Birds show the parts of birds under the section Bird Topography. NBG eaglet HE is showing off her “mantle” above.
Left photo – To “mantle” or mantling refers to when a raptor spreads its wings and haunches over its prey after capturing and while eating it, and is likely a way to prevent other raptors or animals from seeing and stealing their prey. All three NBG juveniles have been seen “mantling” over their food on the web cam.