[obol] Re: Tricolored Blackbird photos from Linn County
- From: Wayne Hoffman <whoffman@xxxxxxxx>
- To: "W. Douglas Robinson" <w.douglas.robinson@xxxxxxxxx>
- Date: Fri, 18 Jul 2014 09:09:23 -0700
Hi -
Good find.
I am writing to comment on a couple of somewhat subtle aspects of epaulet
color.
1. If you look carefully at the fourth photo (lose-up of ad. male facing
right) you can see that the white band does not look completely white at
the front end, where it meets the red. On my monitor it shows a bit of
buffy or creamy infusion in that area. I am not sure if this is pigment,
or if this is filtered red from underlying feathers? but this is not rare
in Tricoloreds. I have photos of birds that show more of this. So the
point is, Tricoloreds have white, not yellow, in their epaulets, but it is
not always stark white from end to end. The separation from Red-wings is
not quite as complete as the field guides tell us.
2. As the field guides say, the red of Tricolor epaulets is darker and
"purer" (without orange tones) than that of Red-wings. However, the actual
shade of red is not identical on all Tricolors. It probably does not
overlap with our local Red-wings, but some are darker red than others.
This should not be a surprise, as red and pink colors in birds tend to
come from pigments obtained in diets, and different individuals may obtain
more or less of these. In some other birds, ability to obtain and express
these pigments is correlated with health (e.g., birds with heavier parasite
loads tend to have less in their feathers) and may even be used by females
in choosing mates. As far as I know, this kind of research as not been
done with epauletted blackbirds, but I do see color variation in the red.
3. My final point is that the red shade variation can be exaggerated in
photos, both in-camera, and as expressed on computer monitors. For
example, if you let a camera set the exposure of a blackbird, particularly
spot-metered, it is likely to overexpose it, compared to how it would
expose a paler bird in the same light. This will make the red look less
saturated than on a less-overexposed photo. (On the other hand this
relative overexposure will tend to bring out texture in the black feathers,
and you may prefer the image that way). If you have not carefully
calibrated the color balance of your monitor, it may affect the shade of
red (and of the white) quite a bit.
So, in the field and with photos, it is good to use other information for
identification in addition to the epaulets: overall size and shape, bill
size and shape, plumage of females, and voice. Most of the Tricolors I
have seen in Oregon have been in places where Redwings are also present, so
direct size/shape comparisons are often available. Tricolors tend to be
gregarious, and females are more distinctive from Redwings than males, so
if you find a questionable male, look around for females.
Wayne
On Wed, Jul 16, 2014 at 3:09 PM, W. Douglas Robinson <
w.douglas.robinson@xxxxxxxxx> wrote:
> https://www.flickr.com/photos/114081245@N06/14485173447/in/photostream/
>
> I have not found any mention of previous Linn County records, although
> surely there must be some.
>
> If you are staying inside and considering July to be terribly boring
> birding, reconsider. Tons of birds moving around to favorable foraging
> areas (often riparian zones), lots of young-of-the-year everywhere, and new
> arrivals of shorebirds every day. July and August are really super times
> for birding in Oregon!
>
> Have fun
> Doug
>
>
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