I watched this Black-bellied Whistling Duck (Dendrocygna autumnalis) pair take turns bathing. One stayed on alert while the other splashed and then they switched roles. Reassuring to know that your lifelong partner has your back. Plus, you want to be sure to look your best for your close-up.
And yes, they do whistle, primarily while flying (though personally, I think they sound more like a dog’s squeaky toy).