(12) In described cases of eagles with this syndrome, all remiges and retrices are malformed, (9,13) and contour feathers are sometimes malformed to varying degrees as well.
For classification as POS, feather alterations in white-tailed sea eagles had to meet 6 or more of the following criteria: 1) loss of all or most flight and tail feathers and eventually covert feathers during the nestling or fledgling period (Fig 1); 2) longitudinal splitting or deformation of the rachis of the primary or secondary feathers and retrices (Fig 2b); 3) excessive keratin deposition on the ventral side of the rachis (Fig 2c); 4) extremely shortened primary and secondary feathers and retrices, including the calamus (Fig 3); 5) curved appearance of the primary and secondary feathers and retrices; 6) replacement of lost abnormal flight and tail feathers by new abnormal feathers; 7) new feathers easily removable; and 8) constriction of the distal part of the calamus.
(33) Very similar to the condition in white-tailed sea eagles, the goshawk fledglings with POS had malformed retrices, coverts, and primary and secondary feathers and were not able to fly.
