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 ; dpadams@gmail.com ; 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”
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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