Colleagues,
I have been reading the exchange of emails on scrub-wren eye colour, and
think that Stephen Ambrose's hypotheses have value. I have also just spoken
with Graeme Chapmen on the phone.
So I'll share with you all recorded iris colours on scrubwrens in the ANWC
from relevant areas:
Mt Lofty Range. Adult-plumaged males (n=7): cream (3), mid cream (2),
cream-buff, cream-ivory. Adult-plumaged females (n=5): cream (2), mid cream,
cream-buff, yellow. No juveniles.
Kangaroo Island. Adult-plumaged males (n=5): pale yellow, pale straw, straw,
pale grey-brown (probably subadult), pale cream-grey. Adult plumaged females
(n=4): pale grey (2), pale grey-brown (probably subadult), pale buff. No
juveniles.
Wet forested southwest corner of WA. Adult-plumaged males (n=7): cream (2),
creamy-white, creamy-grey, greyish cream, pale greyish cream, mid brown
(probably subadult). Adult-plumaged females (n=2): pale cream-grey (2).
Juveniles,(by plumage (n=4): creamy-white, dirty cream, mid cream, mid
creamy grey.
Shark Bay/Houtman Abrolohos: Adult-plumaged males (n=3): off-white
(Abrolhos, 1), light green (Shark Bay, 2). Adult -plumaged females (n=5):
off-white (Abrolhos, 4), light green (Shark Bay).
Now there is subjectivity of colour interpretation by different collectors
here and probable bias from dulling (darkening?) of irides between time of
collection and its recording on the specimen bench in the field. Nonetheless
it also shows that the issue is complex and that a more extensive
photographic record is needed before we can be certain of regional
differentiation in iris colour. Those photographs that are available I
accept as accurate. I also think it likely that the descriptor "grey" in
irides quoted above refer to the "blue" irides Graeme has been talking
about. These, from their photographs, I would interpret as pale bluish white
or pale blue-gray white, the same colour as the peri-orbital skin of Cacatua
triton (galerita superspecies) in New Guinea.
Cheers,
Dick
-----Original Message-----
From: Geoff Shannon
Sent: Sunday, 29 April 2018 5:09 PM
To: Graeme Chapman ; Mike Carter
Cc: ; Dr. Richard Schodde ; Stephen Ambrose
Subject: Scrubwrens
Just to add picture, male and female Tasmanian Scrub- wren April 2018.
Interesting discussion.
I am interested if anyone has good reference to the physiology /
biochemistry etc on eye colour changes. Is it just age or are there other
factors? There has been some discussion with Brown Thornbills ability to
change colour seasonally or even acute stress. I do not have references.
Thanks
Geoff Shannon
On 27/04/2018, 4:04 PM, "Birding-Aus on behalf of Graeme Chapman"
< on behalf of
> wrote:
Hello Mike,
Thank you so much for replying to my request. I'm attaching my K I image
that should have been attached to the original but was removed somehow in
birding-aus.
I'll agree, your bird's eye has a greenish tinge but it is also rather
dark and dull and in my opinion, a probable young bird.
I've been looking at the books on this one and what a can of worms! In
HANZAB you can take your pick in the text on soft parts and in the plate, it
shows maculatus with a yellow eye, which is wrong. The new CSIRO "guide"
opts out altogether on iris colour in the text and the plates are really too
small be of any use on this subject. What a pity this book wasn't published
as a concise handbook in A4 format. They obviously have all the information
but it has been compromised by shoehorning into too small a space.
What I am fairly sure about is that age is a factor here as it is with
many of our small birds - we know so little because so few of our birds have
been studied in detail.
I have a wide range of pics of this species and I'm attaching a few
examples
The first two are Brown Scrubwrens from Tasmania. The first one is an
adult male at the nest - I would describe that iris simply as yellow.
The second bird at the same nest I always assumed to be a female (on
plumage) but it has an olive coloured eye - such dull colours are usually
characteristic of younger birds and it is much more likely to be a helper
than the adult female, or if it is the female it is a younger bird. I don't
expect the sexes to have different coloured eyes as adults. This eye colour
reminds me of your K I bird.
The next pic is what I regard as a classic frontalis and I would
describe that as pale yellow - virtually all east coast birds are like this,
maybe a bit darker as you go north.
The last is the old "Buff-breasted Scrubwren" of the 1926 Checklist from
northern NSW, slightly darker yellow.
I guess what I am on about here is the difference between "Spotted" and
"unspotted" birds. All the Spotted ones I've seen have the pale blue eyes,
which gives them a totally different (to me) look.
So. how long do they take to become adult ( by eye colour )? I'd say at
least two years.
I guess I'm on the same bandwagon as my recent comments on Eastern
Whipbirds. Most of the books get that one wrong and show adults with brown
eyes, whereas in fact they are cream. How long it takes nobody knows but
it's likely to be similar to the Grey-crowned Babbler which is four years.
What really started this interest was the years I spent with Ian Rowley
studying corvids and choughs, both of which can be aged by eye colour, a
very handy indicator when you are looking at life history. We worked with
birds we banded in the nest, so we KNEW how old they were. Getting to the
Australian Raven's nests was interesting, I can't even lift a rope ladder
any more, let alone climb one.
Cheers
Graeme
Spotted Scrubwren from Kangaroo Island - eyes pale blue
>
Brown Scrubwren male at nest, eyes yellow. I assume this is an adult.
Brown Scrubwren at nest, probable immature, eyes olive.
White-browed Scrubwren, Gloucester NSW. eyes pale yellow. Virtually all
east cost birds are like this,
White-browed Scrubwren. Tooloom northern NSW subsp.laevigaster - eyes
yellow
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