Wikipedia
Presbyornithidae is an extinct group of birds with a global distribution. They had evolved by the late Cretaceous period and became extinct during the early Miocene. Initially, they were believed to present a mix of characters shown by waterbirds, shorebirds and flamingos and were used to argue for an evolutionary relationship between these groups, but they are now generally accepted to be waterfowl closely related to modern ducks, geese, and screamers.
They were generally long-legged, long-necked birds, standing around one meter high, with the body of a duck, feet similar to a wader but webbed, and a flat duck-like bill adapted for filter feeding. At least some species were social birds that lived in large flocks and nested in colonies, while others, like the Wilaru species, were terrestrial and solitary.
As the "wading duck" moniker implies, they were waterfowl whose elongated legs enabled them to live a lifestyle similar to the "proto-flamingos" (e.g., Palaelodus) – which were not really ancestors of the modern flamingos, but a group that evolved in parallel with them and in fact seems to have taken over part of the presbyornithid's ecological niche after the latter became extinct. Thus, while probably somewhat capable of swimming, they would have preferred to strain the shallow waters of their habitat for food and were also able to snatch up insects and small crustaceans on dry land, just like some species of modern ducks, e.g., the Laysan duck, hunt for brine flies.