Hi David,
There are some points in your comment that need some further thoughts:
1. It is likely that prey takes the time (i.e. a tiny fraction of a second) to identify a raptor and they are mostly much better than we are in doing so. E.g. there are species that certainly would laugh at a male Collared Sparrowhawk but should be quite concerned about a female Brown Goshawk.
2. “Unrelated but similar looking” = Convergence (adaptation of unrelated taxa to similar ecological niches). E.g. raptors – falcons, raptors – owls, owls – frogmouths, swifts – swallows, herons – cranes, storks – cranes, diving-petrels – auklets, quail – button-quail…
3. “Related but different-looking” = Divergence (adaptation of related taxa to different ecological niches). E.g. ibis – spoonbills, crakes-rails-swamphens-moorhens-coot, frogmouths – nightjars, owlet-nightjars – swifts – hummingbirds, grebes – flamingos…
4. The paragraph starting from “For what it’s worth, Australia has fewer” to “could be more “recent” self-introductions that haven’t had as long to diverge?” Where does all that come from? Divergence is adaptation of related taxa to different ecological niches. I don’t think that this is explained by your thoughts. Why are hawks, pigeons, parrots, rails and so on excellent dispersers? Yes, some raptors are nomadic, some are migratory, but an awful lot is sedentary.
5. In both IOC and Clements Brown Goshawk and Collared Sparrowhawk are not each other’s closest relatives (I haven’t had the chance to look up the original work behind that). That suggests rather convergence than lack of divergence. I am happy to be corrected here.
6. Some of these Accipiter pairs may be just a coincidence because there are many similar-looking Accipiters distributed world-wide. In other words I could ‘put together’ many further “Accipiter pairs”. I guess the Cocos Keeling Island birders can tell you some stories…
7. Yes, a Harpy Eagle with its short rounded wings is adapted to hunting in/under the canopy!
Cheers,
Nikolas
