Even though geese have down plumes and feathers, they are not the same thing. Down plumes are extremely light, three-dimensional structures that trap heat. They also loft up, are very resilient to compression, and do not contain a quill shaft. Feathers, on the other hand, are two-dimensional in shape, and are based on a tubular quill shaft. While feathers do offer a bit of insulation, the weight-to-warmth ratio is nowhere near as high as a down plume.
