Thanks to all those that clarified what this bird is likely to have been. It was indeed a Cooper's Hawk but here are a few replies that I think properly address the situation. By the way, I've seen a Cooper's every week for months now so this may be the same bird. Because it was hanging in the same area as the migrant hawks today, spiralling overhead, I didn't think of it as the same bird that is usually darting about. Brian Morin Cooper's doing their courtship flight display often fluff their white undertail coverts over the top of their rump, appearing much as you describe it. Is it possible that's what you saw or was it true albinism? - Ron Pittaway I've noticed that some territorial Cooper's Hawks puff up their white undertail coverts enormously while soaring over their territories - part of their territorial display done at this time of year. The large ball of white feathers is very prominent from below, and sometimes wraps around the tail and can partially obscure the rump, making it look white - at least along the sides. I've not seen one that completely obscured the rump, but perhaps this might explain what you observed? - Mike Cadman All accipiter's,when displaying [at this time of year] fan their white undertail coverts broadly,to either side of the tail. >From the side,or below,this looks like a white rump,although actually the rump is mostly obscured by the UTCs. Displaying accip's also have a peculiar,floppy flight,with deep,languid wingbeats.......almost looking like SE Owls. I would bet that this Cooper's is territorial.I have a territorial Cooper's around my house,and see it daily,in display flight with the UTCs spread outward. Hope this helps. - James Holdsworth
