Presbyornis

Presbyornis is an extinct genus of water bird. It was a wading bird, often walking in shallow water on its long legs.
"Presbyornis" was one of the first anseriforms. Because of its long legs and neck, it was initially mistaken for a flamingo. Later it was reclassified as an anseriform when the duck-like anatomy of its skull and bill was found. It is from an extinct group closely related to ducks and geese. Judging from numerous fossil findings, "Presbyornis" probably lived in colonies around shallow lakes. Its broad, flat bill was used to filter food (small plants and animals) from the water, in the manner of today's dabbling ducks.
The fossil record includes many complete skeletons from Green River Formation sites (early Eocene). This suggests that the birds nested in colonies, similar to many colony-nesting waterfowl or shorebirds today. Species of this bird have also been found in Maryland, Utah, England, and Mongolia.
Fossils are held in the Smithsonian Institution, the Natural History Museum, London, and the KUVP.