Arachne:
"I hear that not using shampoo is better for the oil levels in your hair," said Arachne. "Do you need shampoo for your feathers?"
"The trick is finding a way to reduce the oil level enough to get the dirt out without getting them waterlogged," Duckling said. "Real water birds can reapply oil from a gland in their butts, but I just have to let it build up naturally. There's like two brands that have exactly what I need, and one of them is German, so you can't get it in a drugstore."