Not a “hunch-back”, but an eagle owl leaning foreward and delivering the “reefed tail” display. I have observed it only three times in GHOs in the wild, but during over 30 years of treating and rehabilitating several hundreds of raptors (including over 50 GHOs) I saw the display repeated several times by a few individual owls. My tentative (note: NOT definitive...) conclusion as to its significance was that it seemed to be delivered as a response to perceived menace when, for some reason, the owl was unable or disinclined to leave the area of the confrontation (as when confined for treatment/rehabilitation).
The incidents of observing the display in wild GHOs: a parent owl would perform the display during human visits to the nest for the purpose of blood sampling and oreo-pharyngeal swabbing of nestlings for rabies virus disease research purposes.
The display was often accompanied by bill-snapping, but not by vocalization. The performing adult seemed to be taking a break from more vigorous attacks on the nest invaders. Head, neck and shoulder protection was provided to the nest invaders!

I saw the same display delivered repeatedly by a captive eurasian eagle owl (same genus as the GHO (Bubo sp.) in a raptor display near BadWorishaven, Bavaria.

Dave

Not a “hunch-back”, but an eagle owl leaning foreward and delivering the “reefed tail” display. I have observed it only three times in GHOs in the wild, but during over 30 years of treating and rehabilitating several hundreds of raptors (including over 50 GHOs) I saw the display repeated several times by a few individual owls. My tentative (note: NOT definitive...) conclusion as to its significance was that it seemed to be delivered as a response to perceived menace when, for some reason, the owl was unable or disinclined to leave the area of the confrontation (as when confined for treatment/rehabilitation).
The incidents of observing the display in wild GHOs: a parent owl would perform the display during human visits to the nest for the purpose of blood sampling and oreo-pharyngeal swabbing of nestlings for rabies virus disease research purposes.
The display was often accompanied by bill-snapping, but not by vocalization. The performing adult seemed to be taking a break from more vigorous attacks on the nest invaders. Head, neck and shoulder protection was provided to the nest invaders!

I saw the same display delivered repeatedly by a captive eurasian eagle owl (same genus as the GHO (Bubo sp.) in a raptor display near BadWorishaven, Bavaria.

Dave

Not a “hunch-back”, but an eagle owl leaning foreward and delivering the “reefed tail” display. I have observed it only three times in GHOs in the wild, but during over 30 years of treating and rehabilitating several hundreds of raptors (including over 50 GHOs) I saw the display repeated several times by a few individual owls. My tentative (note: NOT definitive...) conclusion as to its significance was that it seemed to be delivered as a response to perceived menace when, for some reason, the owl was unable or disinclined to leave the area of the confrontation (as when confined for treatment/rehabilitation).
The incidents of observing the display in wild GHOs: a parent owl would perform the display during human visits to the nest for the purpose of blood sampling and oreo-pharyngeal swabbing of nestlings for rabies virus disease research purposes.
The display was often accompanied by bill-snapping, but not by vocalization. The performing adult seemed to be taking a break from more vigorous attacks on the nest invaders. Head, neck and shoulder protection was provided to the nest invaders!

I saw the same display delivered repeatedly by a captive eurasian eagle owl (same genus as the GHO (Bubo sp.) in a raptor display near BadWorishaven, Bavaria.

Dave