I don't know I've ever seen their LEGS in such detail, and their bluish, knobbly little knees!
This is all very detailed, while at the same time it looks like you didn't have that huge amount of light (the sky was overcast), so I wonder how close you got actually move in on that gull? It must have let you get fairly close (?).
I don't think I was that close, I was shooting with a 40-150mm lense using 100mm as focal length at f11 for 1/40th sec iso 100. Most birds I encounter are very wary of humans so close is not an option. My cat can get much closer by pretending not to be interested and keeping her tail still. She grabs a few inches every time the bird looks away. Maybe I should get a little DSLR feline harness and cut her loose one day