[texbirds] Re: Slaty-backed Gull mantle color
- From: Chuck Sexton <gcwarbler@xxxxxxxxxxxxx>
- To: TexBirds TexBirds Posting <texbirds@xxxxxxxxxxxxx>
- Date: Mon, 17 Feb 2014 08:32:11 -0600
TexBirders,
I think more needs to be said about this topic, actually. The Laredo bird and
Slaty-backed Gulls in general are *not* “black-backed” gulls. I am certain I
overlooked the Slaty-backed Gull on my first afternoon at Lake Casa Blanca on
Wed., Feb. 12, because I was erroneously expecting a very dark-backed
(blackish) gull. Some of the pics of that individual from the LBF weekend
appear quite black-backed. In the late afternoon sun on Wednesday, I kept
looking past the one (distant) large Herring-type gull which seemed to have
just a slightly darker medium gray mantle. Yet in hindsight, I’m sure it was
the Slaty-backed.
I believe what Dan’s link to the Surfbirds.com pics of Slaty-backed Gulls was
meant to suggest is that the mantle color is variable (a) among individuals,
and/or (b) by angle and lighting conditions, and/or (c) by photographic
measures. Precisely because the Slaty-backed Gull has an intermediate mantle
color, it can seem to be much lighter or much darker due especially to the
angle of sunlight and cloud conditions. My experience on Thursday, Feb. 13,
with real-time discussion with several birding friends as we looked at the
(known) Slaty-backed through 20X to 60X scopes continued to emphasize how time
of day, side lighting, and shadows could deceive the eye into believing the
mantle color of the Laredo bird could be virtually anything from pale Herring
gray to Black-backed.
Chuck Sexton
Austin
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