Collared Sparrowhawks anyone?

["Philip Veerman" <>]

Hello Paul,

 

Yes I think that is a very good observation. This on the basis that, pigmentation deficiency, is typically not perfectly symmetrical (as for example in often happens in ducks, chickens, blackbirds, the recent ones in ravens and the one Pied Currawong I found during one of Lindenmayer's surveys at Nanangroe). It certainly appears to be symmetrical this photo, or this case.  That does not mean that a genetic change would not cause a pigmentation deficiency (or any other words we may happen to use) that happens to be symmetrical. I think it would need a really clear close look at the bird and some history to work out this one. Or maybe a look at lots of museum specimens, although looking into the closed wings is not so easy.

 

Philip Veerman

24 Castley Circuit

Kambah  ACT  2902

 

02 - 62314041

-----Original Message-----
From: Paul T. [
Sent: Saturday, 15 August 2009 10:31 AM
To:
Subject: RE: [canberrabirds] Collared Sparrowhawks anyone?

At 05:37 PM
14/08/2009, you wrote:
> Yes. On the basis of the tail shape is really obvious. It also
>   shows big white spots. Is that a recent thing? I commented several weeks back
>   that these are likely to be pale feather bases made visible during moulting.
>   However this and a few other recent local photos suggest I was wrong in that.
>   Are we getting a plumage pigmentation deficiency?

Philip
et al,

If it was a pigmentation deficiency, would the effect be perfectly
symmetrical?  If you look at the white feathers (or part feathers) on
either wing they match absolutely perfectly (allowing for one white patch which
looks like it could be covered by a brown feather on the other wing?). 
Unless all these feathers grew at the same time (and coincided with a deficiency
or something that can cause feather bleaching) would they be perfectly mirrored
like this?  What are the odds of all those feathers being replaced at
exactly the same rate?  Is it possibly just a genetic "colour form" unique
to this bird?

Fascinating picture, that is for sure.

Cheers.

Paul T.
Higgins, ACT *******************************************************************************************************