finding rare birds

people have in the past often asked me how you find rare birds: I have always put it down to 80% luck and 20% persistence but one key method is to concentrate on the birds that you have in numbers and try to locate the oddment amongst them -- in the last few days I have found up to 10 Mediterranean Gulls and 3-4 Yellow-legged Gulls amongst the 1000's of 2cy Common and Lesser Black-backs using the patch for bathing and roosting; I was seriously hoping for the first Caspian Gull of the year so have checked the gulls three times today; tonight the 80% luck played its part; most of the big gulls flew off as I sat down to scan leaving 5 Meds and lots of Commons plus a few LBBG and 4 Yellow-legs -- the 80% luck involved a small gull raising its head from its back just as I scoped by it to suggest a black and fine bill? a grey nape was the only other feature I could see as it sat facing me and stayed asleep for the next 25 minutes; in fact in the next three and a half hours it was asleep for 90% of the time so that chance sighting of its bill was more than fortuitous -- here is the view that I had for the first hour waiting for another look at the bill and eventually the legs -- not the ost obvious of rare birds from this view