The 'Shite Hawks' or 'Urban Gulls'?

The same garden perch,but this time occupied by the Urban predator Gull.
We have started to feed the wild birds,but of course the Gulls spot the food on my garden shed roof,and they will eat any and all of what we put out?
This one I would suspect as being quite young,as it still has signs of its juvenile
feathers around its neck!
This time I have used my D800 with DX crop +the Sigma 150-500 @500 = 750mm.I was very pleased with the detail in the feathers,as I should be I suppose being as the camera cost me £2000??
There are times I still think the D3 has the edge on sharpness but I suppose I still have a lot to learn about the D800? It's still early days!