I’d love to know the answer to that. Also with the superficially very similar Black-shouldered Kite and Letter-winged Kite, why so similar when perched, and why the different underwing pattern and eye marking?
Peter Shute
Sent from my iPad
On 11/01/2013, at 5:10 PM, “Philip Veerman”
> After contributions from several people to solve the recently Birding-Aus > posted “Timeless question” of a request to identify some photos as either a > Collared Sparrowhawk or a Brown Goshawk, it got me wondering has anyone > investigated or got any ideas why these two species are so similar in the > colour patterns and remarkably so in both juvenile & adult plumages. The > first bird book I ever bought was Condon’s 1966 Field guide to the hawks of > Australia when I could afford the 50 cents RRP. It said (snippets) that they > have “the same pattern, that the Collared Sparrowhawk is a small replica of > the Brown Goshawk and the female cannot be distinguished from the male Brown > Goshawk in the field and they can only be picked in museum skins”. Well now > we know better but the point remains that their colour patterns are > amazingly similar. > > As hawk species go, both their colour patterns in juvenile & adult plumages > are an unremarkable sort of typical for the genus as a whole. But why are > these two so much more the same than any others. Is it common ancestry that > these two species are a more recent divergence from each other than to any > other members of the genus and have changed in size and structure but not in > colour. It appears to me that in structure their form is divergent along the > lines of other species of Sparrowhawks and Goshawks. Why should our Brown > Goshawk look so much more like our Collared Sparrowhawk than say the > widespread European Northern Goshawk? Could it be colour mimicry of one > species of another, in which case why? Is it coincidence, and especially > that they inhabit the same geographic range. Nikolas Haass has mentioned > that the Cooper’s/Sharp-shinned Hawk pair causes in N America very similar > confusion issues as the Brown G/Collared S pair in Australia. Does the same > question apply? > > Philip > > > > =============================== > > To unsubscribe from this mailing list, > send the message: > unsubscribe > (in the body of the message, with no Subject line) > to: birding-aus-request@vicnet.net.au > > http://birding-aus.org > =============================== ===============================
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