Baby Ducks' Bills Changing Color! Need Help!

[marvelfanatic22]

Hi everyone!

I see a female Muscovy duck with 9 babies, and recently I noticed that about 3-4 of the ducklings' bills are changing color. They are around 4-6 weeks old. They are darker colored ducklings so they all were born with dark purplish bills. But today, I see some of their bills are turning more light purple greyish. Should I be concerned? Are they sick or is bill changing color common?

 

[sourland]

Without pictures it is difficult to be sure, but I would guess it is just normal development as long as they are eating, drinking, and growing.