birding-aus

'phases' of Brown Falcon

To: Birding-aus <>
Subject: 'phases' of Brown Falcon
From: "John Leonard" <>
Date: Tue, 25 Apr 2006 10:14:08 +1000
That's good, thanks for this, I wonder what to make of the very pale grey
birds that can be be mistaken for Grey Falcons?

John L

On 4/24/06, Andrew Taylor <> wrote:
>
> On Mon, Apr 24, 2006 at 04:02:34PM +1000, John Leonard wrote:
> > Alan Morris alluded to an article in the Emu which has proved that the
> > phases of the Brown Falcon are age-related colour changes.
> > Could someone summarise this article in a few sentences for us? Alan?
>
> Courtesy http://www.publish.csiro.au/nid/96/paper/MU02028.htm
>
> Variable plumage and bare part colouration in the Brown Falcon, Falco
> berigora: the influence of age and sex
>
> Paul G. McDonald
>
> Abstract
>
> The Brown Falcon, Falco berigora, is one of Australasia's most common
> raptors, yet considerable confusion remains over the influence of
> geography, age and sex on plumage and bare part colouration in this
> species. To address this issue, 160 immature and adult falcons from
> an individually marked, closely monitored population were examined. In
> contrast to previous studies, all were of known sex, age-group and part of
> the resident population or their offspring. Adult males had significantly
> lighter upperpart, cap, ventral and underwing covert plumage in comparison
> with other birds, closely resembling what has previously been described as
> a 'rufous morph'. Immature females were significantly darker than other
> ages and sexes in upperpart and underwing covert plumage, resembling
> descriptions of 'dark morphs'. In contrast, plumage of immature males
> and adult females tended to be similar and intermediate between these
> extremes, resembling the 'brown morph'. The buff-tinged, not white,
> ventral plumage and darker underwing covert plumage of immature males
> separated them from adult females. Cere and orbital ring colour also
> differed with sex and age: immature females had the dullest facial bare
> parts and adult males the brightest, adult females and immature males
> again being intermediate between the two. The results indicate that most
> variation in plumage and facial bare part colouration observed in the
> population could be attributed to age and sex differences as opposed to
> racial clines or the existence of colour morphs. Moreover, the brighter
> colours of adult falcons may function as honest signals of quality.
>
> Emu AUSTRAL ORNITHOLOGY 103(1) 21 - 28 2003
>
> Andrew
>
>


--
John Leonard
Canberra
Australia
www.jleonard.net
==============================www.birding-aus.org
birding-aus.blogspot.com

To unsubscribe from this mailing list,
send the message:
unsubscribe
(in the body of the message, with no Subject line)
to: 
=============================
<Prev in Thread] Current Thread [Next in Thread>
Admin

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the birding-aus mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU