I was speculating a little, but based on the fact that the white underparts
of seabirds has been shown to be for camouflage in the sky (although for
aquatic prey). White is an unusual colour in nature, and my general
impression is that it's much more common in birds than other animals, and
more common in birds that are more exposed - as generalisations of course,
there are obviously exceptions.
On 13 January 2013 09:27, Greg and Val Clancy <> wrote:
> Whether there is any scientific basis for the ‘cockatoo theory’ or not
> I am sure that the white underparts would assist in camouflage in the sky.
>
> Greg
> Dr Greg. P. Clancy
> Ecologist and Birding-wildlife Guide
> PO Box 63 Coutts Crossing NSW 2460
> 0266493153 0429601960
>
> *From:* Jeremy O'Wheel <>
> *Sent:* Sunday, January 13, 2013 12:09 AM
> *To:* Rosemary Royle <>
> *Cc:* COG line <> ; ;
> Greg <> ; Denise Goodfellow <>;
> Birding
> Aus <>
> *Subject:* Re: [Birding-Aus] [canberrabirds] Why are the C. Sparrowhawk &
> B.Goshawk so similar?
>
>
> The problem with the cockatoo theory is that in Tasmania there is good
> reason to think Sulphur-crested Cockatoos are recently introductions, but
> all the Grey Goshawks are white morph. Also Grey Goshawks have a white
> underside regardless of morph, and that's the side prey would normally see.
> I suspect the underside is white for sky camouflage (like the
> White-breasted Sea-eagle and a number of other diurnal birds of prey),
> while the upper surface possibly represents genetic drift, or sexual
> selection.
>
> Jeremy
> On 12/01/2013 11:56 PM, "Rosemary Royle" <> wrote:
>
>> During our latest trip to Australia, up above Gunlom Falls in the NT we
>> spotted a dead branch laden with Sulphur-crested Cockatoos plus what
>> appeared to be a smaller white cockatoo. It wasn't, it was a white-morph
>> Grey Goshawk, and it had obviously chosen to perch with the cockatoos. .
>>
>> Only on reading this thread does that sighting make sense.
>>
>> Rosemary
>>
>> Rosemary Royle, Wales, UK
>>
>>
>>
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