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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