A blind man unwittingly packed Heathcliff into a bag of crumbs. He has cleverly made a disguise out of a majority of said crumbs while lying in wait. The blind man, fond of talking birds, throws Heathcliff out as food, but the birds, having enough brain power to speak, aren't fooled, because Heathcliff is a floating, whistling cat. No amount of bread can mask that.