I've posted this before but make no apology. It's close up of a female Shoveler which shows "bristles" on her mandibles.
If you've ever watched a pair feeding, going round in circles with their heads submerged I think they are using these bristles to filter out whatever they are eating. I think in the case of a pair there's probably an element of bonding too.
Aren't birds amazing.
Northern shoveler, known simply in Britain as the shoveler,