Believe it or not this is a Little Egret fledgling. Structurally it’s identical to its siblings, two other Little Egrets with fairly typical bill colours, darkening pinkish/orange and this bird has been seen being fed by its presumed parent, an adult Little Egret. Some research suggest that juvenile Little Egrets can look like this occasionally, i.e. have bright orange bills but I have yet to see any pictures or mention of this in any book. An interesting bird and an undoubted pitfall many of us must be unaware of.