G'day Paul,
I must admit I am not personally sold on the idea of a different age
structure for brown Falcons of the Central Australian region but I am still
keen to listen to all ideas on this. I have now collected a lot of images
from Central Australia of pale and rufous type adults and as Chris Watson
has already mentioned at the start of this thread they predominantly have
yellow soft parts, excluding the young birds. It looks like the norm for the
area to me based on the photos, but this is clearly not a definitive answer.
None of the photos were taken because the photographer was aware of the soft
part colouration so it is a completely unbiased collection.
I am very keen to see images of birds from your Werribee study showing the
yellow facial soft parts, do you have any you can send me.
Cheers Jeff.
-----Original Message-----
From:
On Behalf Of Paul McDonald
Sent: Thursday, 6 October 2011 8:36 AM
To: Richard Nowotny
Cc: Birding-Aus Birding-Aus
Subject: Brown Falcons with yellow cere and bare facial
parts
Dear Richard,
Seems that you now have the paper, but let me know if you need another copy
or anything else to do with that project.
As I said in my last B-Aus post, I'm less convinced by the regional colour
differences argument, but granted have not spent a huge amount of time in
western central Australia or indeed the Kimberley. That said, dark
individuals are not uncommon in SE Aust. As sex/age differences were largely
overlooked at Werribee, one of the most commonly birded sites in the
country, it seems likely that we don't have a clear idea of what is
happening in more rarely visited areas that haven't been the subject of
colour banding studies/longitudinal. I also think that central Australia is
likely to be a more harsh environment for young (greater stochasticity in
prey availability?), but perhaps better for adults (good conditions with
experience/once a territory is established etc). Both factors could lead to
skewed age distributions in the population, such that males in these areas
are predominately older than elsewhere, and thus lighter and redder. The
other factor is that young birds wander f
or a year or two after fledging before settling, so if these young birds
preferentially stick to one area, say central west of NSW, by default that
region becomes 'darker' while western areas would become lighter and redder
by the age distribution within the population.
Note that I'm not suggesting that this occurs in NSW specifically, but
rather that until we have some detailed studies of these apparently aberrant
areas I remain unconvinced of the true veracity of these plumage
phases/types and so on. It is possible that many young birds leave the
central regions to reside in the Kimberley, for example. However, I'd very
happily be proved wrong if someone wants to do the work, as they are a very
special bird that many ignore due to their common nature.
Hopefully this will let people look at these birds a bit more closely, and
also jog the field guides into updating their information.
Cheers,
Paul
On 05/10/2011, at 11:06 PM, Richard Nowotny wrote:
> THANKS JEFF. FURTHER HELPFUL COMMENTARY FOR ME, AND I HOPE OTHER READERS
AS
> WELL. MY COMMENTS BELOW THUS: ****........**. REGARDS. RICHARD
>
>
>
> I think you have misunderstood what Stephen was saying, three factors to
> consider.
>
>
>
> 1- a given population of Brown Falcons say at Werribee or where ever, does
> not consist of a number of different morphs. The differences in plumage
are
> primarily the result of differences between the sexes overlaid by
increasing
> paleness as the individuals get older. ****THIS WAS INDEED MY
UNDERSTANDING
> - AS REPORTED BY PAUL McDONALD FROM HIS RESEARCH AT WERRIBEE. HOWEVER I
LOOK
> FORWARD TO READING HIS ORIGINAL ARTICLE (A COPY OF WHICH I NOW HAVE).**
>
>
>
> 2- there are regional differences eg. birds in Central Aust are paler more
> "Kestrel like", birds from the Kimberley are very dark. There are other
> features of difference between these regional types beyond pale and dark
> which I am not going to go into here, but the important thing to
understand
>
> is that a pale regional type from Central Aust and a very old pale male
from
> Werribee are not the same thing, they don't look identical. Same for the
> dark Kimberley/Top end birds, there is no equivalent found elsewhere.
These
> are regional types. ****THIS IS HELPFUL CLARIFICATION OF REGIONAL
> DIFFERENCES, OF WHICH I WAS LESS AWARE.**
>
>
>
> 3- yellow cere is apparently only found in the older males especially the
> pale Central Australian population, Stephen suggested this may possibly be
> because they are for unknown reason more likely to reach the prerequisite
> older age. ****THAT WAS MY UNDERSTANDING OF WHAT HE MEANT.**
>
>
>
> Cheers Jeff.
>
>
>
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Paul G. McDonald
Lecturer
Zoology, School of Environmental and Rural Sciences
University of New England
Armidale NSW 2351
Australia
Ph: +612 6773 3317 Fax: +612 6773 3814
Publication list: http://publicationslist.org/paul.mcdonald
Thompson ISI Researcher ID: http://www.researcherid.com/rid/A-5928-2010
Web: http://www.une.edu.au/staff/pmcdon21.php
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