Likely male with the red bill with only the tip black. Female/imm shows more black at least on upper part of the bill. This according to litt. I'm not sure how much variation the female bill can show, but would expect it to show less black in general than what a juvenile does.
Not sure about age or sex. The overall red bill indicates a male but with the blackish edge almost reaching the base of the bill it could also be a female. Or perhaps a young male with a bill almost transformed to a pure adult male bill. Also see 3089 of same bird the day after.