Dear David et al,
Great to see people talking about Brown Falcon plumages again, but
disappointing that David didn't mention an alternate viewpoint. We've debated
this on Birding-Aus previously, so no point going through the details again
that are available in the archives (e.g.,
http://bioacoustics.cse.unsw.edu.au/birding-aus/2011-10/msg00126.html and other
messages from both viewpoints in that thread).
The synopsis is that HANZAB concluded morphs existed in 1993, in 2003 (Emu
103:21-28) I described plumage in marked birds in Werribee, southern Victoria
and concluded that age/sex differences in that area closely resembled many of
the characteristics of the described morphs. Further, plumages of individual
birds also apparently moved between morphs over time. My conclusion from that
was that much of the variation in plumage is thus driven by age changes
throughout an individual's life, with strong patterns associated with each sex.
The fact that this is one area only is irrelevant, the HANZAB text itself
acknowledges that more work is needed to understand these plumages, and by
demonstrating changes inconsistent with morphs in one area, these data justify
re-examination with new data patterns in other areas. This is particularly
important as there are so many intermediate birds between morphs, as HANZAB
also points out, that further cloud the validity of discrete, non-overlapping
morphs. My opinion is that all of this variation is more parsimoniously
explained by linear variation potentially driven by something like age, with
separate patterns for each sex, than discrete morphs with presumably aberrant
individuals between them.
David James disagrees, which is fine, but to ignore the above finding and set
HANZAB results in stone is not how we'll finally get to understand the species.
What we need is detailed information on changes in plumage from individuals of
known age (i.e., more detail than simply adult, as changes clearly happen
after first adult plumage in at least some birds) across the different regions
of their range. Some banders, rehab folk and therefore birders may well be in a
position to start collecting some of this data, which would be very useful,
particularly in problematic areas away from SE Australia. I maintain that until
this is done, the below picture of three morphs alone is not complete and does
not explain all of the observed variation in the field.
Happy to answer further questions off list as this is a well worn debate that
sorely needs new data to progress.
Cheers,
Paul
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Paul G. McDonald
<>
http://www.une.edu.au/ers/research/abel/
Senior Lecturer and Convenor
Zoology, School of Environmental and Rural Science
University of New England
Armidale NSW 2351
Australia
Ph: +612 6773 3317 Fax: +612 6773 3814
Google Scholar: http://tinyurl.com/scholar-google-pgm
University of New England: CRICOS 00003G
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On 04/08/2013, at 8:21, David James wrote:
Hi Greg and Nikolas,
Brown Falcon plumages are very complicated, but they do have actual morphs. The
morphs change with age (i.e they have phases within morphs). What's more, the
morphs also vary geographically and there are slight difference between the
sexes in adult plumage.
there are three morphs, brown, black and rufous. The downy young of all morphs
are the same. The juveniles are similar (brown above and on the thighs and
flanks with buff centre of breast and underparts) but the rufous morph has
broader rufous fringes (scaling) to the upperparts and the dark morph has very
little buff below. In adult plumages of the brown morph the buff becomes cream
and the upperparts become slightly duller and mottled; the rufous morph gets
rufous upperparts and cream underparts, while the dark morph resembles a Black
Falcon. In this way the juveniles are intermediate between the rufous morph
and dark morph, and the former get paler with age while the latter get darker
and the brown morphs don't change so much..
Brown morph predominates in the SE (and is the only morph in Tassie), rufous
morph predominates in the interior and west, dark morph is most common in the
tropics but is comparatively rare (generally, the more humidity, the darker the
plumage, but with exceptions). The distributions are difficult to determine
precisely because there is lots of variation and lots of birds intermediate
between rufous and brown morphs,, Also, the changes with age and differences
between sexes make it even more confusing.
However, the rufous morph probably does not breed on the east coast, so the
bird Greg saw likely was from inland, but not necessarily from very far inland.
Also, in the most arid central deserts there is a very pale version of the
rufous morph that is quite similar to Nankeen Kestrel females, and could be
named the kestrel morph. In HANZAB, I didn't accept any subspecies in
Australia, but previously 5 were recognised. Birds in the SW (all rufous morph,
I think) are slightly smaller than those elsewhere, so you colud separate them
as subspecies occidentalis.
There are more details in HANZAB.
Cheers,
David James
Sydney
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