Hi All,
I've had limited access to the internet over the last three weeks, so I'm
just catching up on the responses to the scrubwren discussion from across
that period.
While I accept that eye colour in scrubwrens is probably influenced by the
age of the individual, I still think there could also be an environmental
component to it. There's been a lot of research in humans that correlate an
individual's health with eye colour. In earlier emails, I've suggested that
blue/plain eyes in individual scrubwrens may be related to their
physiological condition which, in turn, may be related to environmental
conditions to which they are subjected (e.g. salt-loading of their diet,
dietary deficiencies, reflectivity of light). In doing so, I hypothesized a
possible hormonal mechanism for blue/plain eye colour. Therefore, if there
is a variation in eye colour within a single population, then that may
reflect different age groups (as promoted by Jeff), but it may also reflect
differences in exposure to environmental conditions experienced by
individuals. For instance, some individuals within a coastal population may
be consuming a saltier diet than others within that population, depending on
the location of their home ranges in relation to salt deposition across the
landscape or individual variation in access to food. In other words,
blue/plain eyes could denote individuals that are experiencing more
physiological stress (i.e. less healthy scrubwrens) based on their degree of
exposure to local environmental conditions. This may explain to some extent
why some scrubwrens east of Adelaide and on Kangaroo Island have blue/plain
eyes. If the eye colour of adult Spotted Scrubwrens in the wet forests of
the South-west are predominantly yellow or buff, and those found in coastal
dunes are predominantly blue/plain, then I would argue that would reflect
differences in environmental conditions (as well as habitats) to which the
two sets of populations are exposed.
Cheers,
Stephen
Stephen Ambrose
Ryde NSW
-----Original Message-----
From: Birding-Aus On Behalf Of
Jeff Davies
Sent: Wednesday, 9 May 2018 2:14 PM
To: 'Martin Cake' <>; 'Graeme Chapman'
<>
Cc:
Subject: Scrubwrens
Looking at those blogs Martin,
You are picking out the odd bird on those particular blogs with plain eyes
when the majority on the same blogs show buff eyes.
My money is on those odd individuals being subadult or subordinated adult or
whatever, a bit like what happens with Corvids, start out dark, become
pale(even blueish) imms, before eventually becoming breeding adult.
Before you ask, I haven't any research to back this up.
But if the majority of def adult East coast Scrubwrens are showing buff
eyes and you have a handful that don't fit, you don't ignore the majority
view, you look for an explanation as to why the occasional bird doesn't fit.
That Mornington Peninsula bird in particular looks good for an immature.
Looking at the Spotted types, same deal, go through all the photos you can
find and then tally up what the majority appearance is for the adults,
rather than picking out the odd variant.
And the see if the add variants can be accounted for as imms, non-breeding
adults or whatever.
It's the appearance of the overwhelming majority of adults that count in
this comparison.
Cheers Jeff.
-----Original Message-----
From: Birding-Aus On Behalf Of
Martin Cake
Sent: Wednesday, 9 May 2018 12:08 PM
To: Graeme Chapman <>
Cc:
Subject: Scrubwrens
G'day Graeme
Yes interesting puzzle isn¹t it.
I guess we can¹t say whether DNA will have the last word, until it has the
last word!
As for some images of live White-broweds that don't fit the pattern, here¹s
a few examples found from a quick search:
A bird with grey-green eyes at Greens Bush, Mornington Peninsula
https://maltpadaderson.com/2015/01/03/1st-jan-2015-and-a-quiet-start-with-p
hotography-at-greens-bush/
Some weakly-spotted birds with pale grey-green eyes at Cleland Wildlife
Park, in the Mt Lofty ranges
http://tcphotosdotnet.blogspot.com.au/2012/11/cleland-blitz.html
A non-spotted bird with a pale grey eye near Gluepot
http://www.wilddogphotographics.com/page39/page2/
A male with a grey-green eye near Minghorn Gap NSW
https://mdahlem.net/birds/17/wbrscrwr.php
A neutral grey eye from Narrabeen NSW
https://www.birdforum.net/opus/index.php?title=White-browed_Scrubwren&oldid
=163362
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