I actually wonder if the eye colour is related to the amount of light to
which scrubwrens are exposed. For instance, scrubwren individuals that occur
in the undergrowth of forests are likely to be exposed to lower light
conditions most of the time than those that fly between scattered and/or
low-lying vegetation on coastal dunes, where there is often glaring light.
So perhaps eye coloration is important in preventing damage to the eyes
under bright sunlight conditions (such as in coastal dune scrub) or somehow
assisting scrubwrens to see more clearly under the light conditions to which
they are most often exposed (dark or bright sunlight). I did a quick check
of field guides and it appears that scrubwren species in PNG and northern
Australia, where I would expect to find them mostly in low-light
environments, had dark eyes (brown or reddish-brown). Similarly,
Yellow-throated Scrubwrens and Large-billed Scrubwrens, which live in
coastal forests of eastern Australia have dark eyes. Perhaps the yellow-eyed
WBSWs along the east coast of Australia that Graeme refers to are mostly in
lower-light environments than a lot of Spotted Scrubwrens along the south
and south-west coasts, but in more brightly-lit environments most of the
time than those scrubwren species in far north Qld and PNG, so have an
intermediate eye coloration.
Overseas research suggest that eye coloration in some bird species is also
influenced by age, diet and/or reproductive fitness. While diet may explain
in part the geographical differences in eye coloration of scrubwrens, it is
unlikely that age and reproductive fitness would explain the geographical
variation.
Anyway, they are just my thoughts, which may or may not be on the right
track. It's perhaps an interesting topic for someone to take on as a PhD
project.
Cheers,
Stephen
Stephen Ambrose
Ryde NSW
-----Original Message-----
From: Birding-Aus On Behalf Of
Mike Carter
Sent: Friday, April 27, 2018 11:05 AM
To: 'Graeme Chapman';
Cc:
Subject: Scrubwrens
Hi Graeme, Your postscript line implied you were attaching a photo of a
Kangaroo Island Spotted Scrubwren but I couldn't see one. Here is a shot of
mine from Kangaroo Island taken in the late evening. To me the eye seems to
have more of a greenish tinge. Local Victorian birds look white-eyed to me.
Cheers,
Mike Carter, 03 5977 1262
181/160 Mornington-Tyabb Road
Mornington, VIC 3931, Australia
-----Original Message-----
From: Birding-Aus On Behalf Of
Graeme Chapman
Sent: 26 April 2018 10:52 AM
To:
Cc:
Subject: Scrubwrens
Hello Kev,
It would be interesting to me to know the eye colour of the White-browed
Scrubwrens from the Adelaide hills. If anybody knows, please inform us.
Adult White-brows from the east coast have yellow eyes.
All the Spotted Scrubwrens I have seen and photographed have blue eyes - a
very different look.
It has been suggested to me that this might be a latitude thing.
Cheers
Graeme
This is a Kangaroo Island Spotted - might well be closer to White-browed
but DNA isn't the last word.
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