A great blue heron flew past the pontoon boat a few days back.
We went from not seeing any for weeks to having 4 or 5 in one afternoon on the bay.
Great Blue Herons have specialized feathers on their chest that continually grow and fray. The herons comb this “powder down” with a fringed claw on their middle toes, using the down like a washcloth to remove fish slime and other oils from their feathers as they preen. Applying the powder to their underparts protects their feathers against the slime and oils of swamps.
source - Cornell Lab of Ornithology.