Marooned swan

The Caledonian Canal has frozen over, and this poor swan has been marooned for the past few days, on this little pool of water. I may be wrong, but I'm thinking that the animal's urine may be a factor in keeping the ice at bay. Anyway, s/he hasn't been going anywhere, and looking a bit forlorn. (I presume his/her self-preservation instincts are good, as flying off would use up precious calories.) Then, tonight, behold a man from the east arrived with a bag of bread crumbs. This was good as I was about to go and Google, 'what do swans eat?' I shouted across the canal, 'well done sir!' but he didn't respond. Either deaf or not someone who cared to be identified as a hero.