Help with baby seagull please :-(

Hi everyone, does anybody know about seagulls?  A baby seagull flew into a window at my workplace and he landed on the roof outside my window.  He has been there for 2 days now (and still here this morning) and although he doesn't look injured or anything I am worried that he cant fly properly yet.  He seems in good health but there is no sign of the parents coming down to feed him. He has been making a calling noise and there are adult seagulls flying over our office also calling but so far no sign of him flying. He is quite big but still grey with the slightest bit of down at the top of his legs and a tuft or two by his neck.  Would anyone be able to tell how old he is and whether he will fly on his own?  I dont know what else to do.  Any advice would be great, thanks xx