Philip - I won’t go
on and on with the graphics but that group photo from Werribee in November shows
a resting flock of at least 54 avocets and 26 banded stilts (no
black-winged). I counted them by the paintbrush method as shown below,
putting together 3 snaps to get the whole flock in with some detail that could
be enlarged. In response to something Con mentioned this would be a good
method of counting flocks for survey purposes. I remember seeing a high
resolution shot Barry Baker used to count seabirds on a sub-antarctic island,
and I’m sure the same thing is done for waterbird surveys elsewhere in the
country.
Now the same photo examined when
zoomed in on (not this version though) clearly shows varying avocet head
colours. The juvenile birds (just a small number – indicated by a greyish
wash on the white plumage) definitely have paler heads compared to adjacent
adults.)
In view of their preference for
salty conditions, I wouldn’t expect any bandeds here. However I had been
predicting the avocets were due to arrive. I remember the single one we
had at Kellys a few years ago - arriving inconveniently just after
the cut-off for Steve Wilson’s book.
From: Philip Veerman [
Sent:
Wednesday, 2 January 2013 2:02 PM
To:
Subject: [canberrabirds] Plumage
colours
I
had not particularly thought about it but some other questions arise and I don't
know the answers. Are all the Avocets coloured the same? It appears from the
photo that they are not. However I suspect that they are, and the differences
are due to other things. Is the chestnut (or whatever) colour, unvaried,
wherever it occurs. It appears from the photo that the backs of the necks are
often darker than the tops of the head. However I suspect that is not
because of colour of the feathers but because we are seeing through different
numbers of layers of feathers and / or the angle of the light . If the
feathers are fluffed out, we may be seeing only one layer but if sleeked down or
flat against a solid object we are seeing multiple layers of the same colour
which will make it appear darker or maybe browner. Of course also as a water
bird, presence of water may darken the appearance.
By
the way, did we all pick the Banded Stilts in the photo?
-----Original Message-----
From: Geoffrey Dabb
Sent:
Wednesday, 2 January 2013 11:03 AM
To:
Subject:
[canberrabirds] Plumage colours
Thanks for opening up a fascinating subject, Bill, but I
must disagree.
The 'Naturalist's Colour Guide', first part published in
1974, was intended 'to give ornithologists and other naturalists an accurate and
handily available tool to use in describing the colours of birds and other
animals'. It was based on spectrophotometry analysis of actual plumages.
Comparisons were made in the laboratory under precise specifications as to
uniform lighting. It used a code written in terms of hue, value
(light/dark) and chroma (saturation). Fine divisions on those aspects were
expressed in decimals. Colour 240, which came out in Part III after a long
discussion about the confused rufescence issue in Part II, has a code 3.6 YR
4.5/6.7. For practical purposes, this seems precise enough.
A selection of common colours was then published in the
guide. Printing limitations would have been an issue, but great care was
taken to keep the printed product as useful as possible. HANZAB was
prepared using the guide against actual plumages in specified lighting, It
gave 'dark 240' as the best match for the avocet head. The match might be,
in a sense, 'approximate', but I think it can be taken as a scientifically sound
assessment, and any degree of 'approximation' is negligible compared (my main
point) to the enormous variation in apparent colour due to variable light in the
field - or in photographs.
Now we come to the separate question of names for colours,
which was what you raised in your first message. There will be no
agreement on this, unless an agreed nomenclature (take the one in the guide if
you wish) is used. 'Kingfisher Rufous' was just made up. The
important thing is 'Colour 240', which is given by HANZAB for the avocet head.
Now HANZAB itself did not adopt the Guide NAMES: 'these were used by
Smithe only to convey a sense of familiarity'. 'One man's sepia is
another man's fuscous, and so on ... Names of colours given in the text
are simple (eg dark brown) so that readers unfamiliar with complex colour
descriptions(eg burnt umber with a trace of cinnamon) will not be misled'.
I would agree on that basis 'chestnut' is the most general of approximations,
but not 'dark 240'.
Since publication of the Colour Guide the digitising of
colours has introduced a whole new element. The radiant light (if that is
the _expression_) from your monitor, and the possibility of variable colour
setting, are as serious a source of distortion as the limitations of the
printing process, but that is another matter. I couldn’t agree more about
the wonderful effect we are getting at the moment with that early morning
light. Here is my impression of ‘burnished avocets’ – using the ‘colour
stretch’ button on one of my graphics programs.
.
To:
Subject:
Colour on an avocet
From: Bill & Raelene <>
Date: Tue, 01 Jan 2013 17:25:12
+1100
Thank you for the colour codings Geoffrey. HANZAB's
chestnut and 'dark 240' in the colour guide and 'Kingfisher Rufous' are
approximations. Red- necked in the avocet does not mean the primary colour red
but a variation that is somewhere in between a secondary(orange) and tertiary
colour (brown). Rufous means reddish and there will be variations of rufous
depending on light. The heads and necks of the Forde avocets, with the early
morning sunlight glowed with that golden burnish. Though I saw them briefly, the
impression was indelible.
Bill
-----Original Message-----
From: Bill & Raelene
Sent: Tuesday, 1 January 2013 12:11 PM
To:
Subject:
[canberrabirds] avocets at Forde Pond.
What shade would you call that striking colour on the head
and neck? chestnut, sienna, umber, light red, milk chocolate?
Bill Graham
