Someone told me mallard derived ducks go pale through summer and colour up again in autumn. I wasn't sure I believed it, but its true! Mine are all dark now, but they were pale at the end of summer
How about dried peas? I don't give them to my ducks but they are in the pigeon feed and my ducks have discovered the washout drain for the coop....you know, cos ducks are disgusting! I've been worrying about them hoovering up yucky old pigeon feed