From: Nate Dias <offshorebirder@gmail.com>
Date: 2015-07-12 10:08
Subject: Re: mystery raptor NAIROBI NATIONAL PARK 11th July 2015
On Sunday, July 12, 2015, Brian Finch birdfinch@gmail.com [kenyabirdsnet] <kenyabirdsnet-noreply@yahoogroups.com> wrote:
NAIROBI NATIONAL PARK 11th July 2015
...
... Also here was a strange raptor
which defied identification and its images are attached. It was shaped
like a Black Kite, and twisted its tail whilst flying. It was also of
similar size, however it had a rounded, almost wedge-shaped tail. The
bill was grey with a black tip. The upperwing had a curios white mark
present on both wings, this was located across the wing-coverts rather
than the margin, and the inner edge of the wing-coverts was paler than
the leading edge. The tail like the back and wing-coverts were
considerably paler than all of the dark flight-feathers. The
underwings were as dark as the upper side of the flight-feathers, but
the head appeared paler than the breast and the rest of the
upperparts. It is a mystery any suggestions as to what it was most
appreciated, but also the reasons why you think it is what you
suggest.
Brian and all,
Dark morph Booted Eagle is a potential candidate that leapt to mind when I read Brian's description and saw his photos. Perhaps a partially melanistic immature individual? But I am not sure how far-fetched the presence of an immature (non-breeding) Booted Eagle would be in Kenya this time of year. Do immatures regularly stay on the wintering grounds and skip the return to northerly breeding areas during their second year?
Features generally consistent with dark morph Booted Eagle in Brian's photos are the fairly long + wedge-shaped tail, dark coloration above and below, pale marks near the leading edge of the upper wing, size and appearance roughly similar to Black Kite.
But some features of dark morph Booted Eagle do not match Brian's bird. It lacks a pale rump patch, lacks the significant buffy band across the wing coverts, lacks buffy scapular patches, plus a few other issues. But partial melanism might explain darker-than-normal coloration and missing or smaller-than-normal pale plumage areas. And buffy plumage patches often fade to whitish when certain bird species are in heavily worn plumage. And worn / missing feathers can give the appearance of whitish plumage patches. Maybe extensive feather wear explains the small whitish upper wing patches.
So perhaps Brian's bird is a melanistic immature Booted Eagle spending the season in Kenya?
I am by no means confident of this ID possibility, but it was the only thing that seemed remotely feasible to me...
Nathan Dias - Charleston, South Carolina, USA