Fish eagle in the context of "Raptor (bird)"

A water bird, alternatively waterbird or aquatic bird, is a bird that lives on or around water. In some definitions, the term water bird is especially applied to birds in freshwater ecosystems, although others make no distinction from seabirds that inhabit marine environments. Some water birds (e.g. wading birds) are more terrestrial while others (e.g. waterfowls) are more aquatic, and their adaptations will vary depending on their environment. These adaptations include webbed feet, beaks, and legs adapted to feed in the water, and the ability to dive from the surface or the air to catch prey in water.

The term aquatic bird is sometimes also used in this context. A related term that has a narrower meaning is waterfowl. Some piscivorous birds of prey, such as ospreys, sea eagles, fish eagles, fish owls, and fishing owls, hunt aquatic prey but do not stay in water for long and live predominantly over dry land, and are not considered water birds. The term waterbird is also used in the context of conservation to refer to any birds that inhabit or depend on bodies of water or wetland areas. Examples of this use include the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the Wallnau Waterbird Reserve.

Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed and strength, these predators have keen eyesight for detecting prey from a distance or during flight, strong feet with sharp talons for grasping or killing prey, and powerful, curved beaks for tearing off flesh. Although predatory birds primarily hunt live prey, many species (such as fish eagles, vultures and condors) also scavenge and eat carrion.

Although the term "bird of prey" could theoretically be taken to include all birds that actively hunt and eat other animals, ornithologists typically use the narrower definition followed in this page, excluding many piscivorous predators such as storks, cranes, herons, gulls, skuas, penguins, and kingfishers, as well as many primarily insectivorous birds such as nightjars, frogmouths, and some passerines (e.g. shrikes); omnivorous passerine birds such as crows and ravens; and opportunistic predators from predominantly frugivorous or herbivorous ratites such as cassowaries and rheas. Some extinct predatory telluravian birds had talons similar to those of modern birds of prey, including mousebird relatives (Sandcoleidae), and Messelasturidae indicating possible common descent. Some Enantiornithes also had such talons, indicating possible convergent evolution, as enanthiornithines are not considered to be true modern birds.