Omnivorous birds have a diverse diet that includes both plant and animal matter. Their food sources range from seeds, grains, grasses, and fruits to mammals, reptiles, amphibians, fish, insects, and even other birds. The primary food they consume often changes with the seasons, depending on availability. For example, many birds rely on protein-rich animal foods like caterpillars during the breeding season but switch to berries in autumn and winter when insects are scarce.
Omnivorous birds include corvids, ducks, gulls, pigeons, woodpeckers, thrushes, and cranes.
Carnivorous birds primarily feed on meat, which they obtain through hunting or scavenging. Birds of prey, such as hawks, falcons, eagles, ospreys, vultures, and owls, are the most well-known carnivores. Their diet includes a wide range of prey, from small insects and crustaceans to large mammals like monkeys, antelopes, and domestic livestock.
Some shorebirds and wading birds, such as storks, are also carnivorous. They feed on reptiles, small mammals, insects, fish, amphibians, and other invertebrates.
While “carnivorous” describes a general meat-based diet, more specific terms exist for birds that typically consume just one type of prey.
Piscivorous birds are those that primarily feed on fish, including species such as cormorants, sawbills, kingfishers, terns, penguins, albatrosses, and osprey. Many have evolved specialized adaptations to catch their prey, such as sharp bills and powerful talons. Some are also strong swimmers or divers, allowing them to pursue fish underwater.
Partial piscivores often supplement their diet with other aquatic animals including aquatic insects, molluscs and crustaceans.
Piscivores can have a significant impact on fish populations, not only by hunting but also by injuring fish or spreading pathogens. Their presence can also cause stress in fish, potentially affecting their health and reducing their ability to efficiently convert food into energy.
Avian avivores are birds that feed on other bird species. These includes certain raptors, such as peregrine falcons and sparrowhawks.
Avivorous birds have evolved specialised adaptations, such as beaks designed for grasping and crushing prey, and curved talons that allow them to snatch birds mid-flight. They are also strong, agile fliers, which allows them to use speed and surprise to capture their prey. Bird-eating raptors tend to show greater sexual dimorphism than other raptors, with females being larger than males.
Insectivorous birds primarily feed on insects and their larvae, and other small invertebrates such as caterpillars, beetles, grasshoppers, flies, dragonflies, and spiders. Many bird species are insectivores, including warblers, swallows, swifts, nightjars, tits, and flycatchers. Some, like the northern flicker, are highly specialised, primarily feeding on ants.
Insectivores catch their prey through various techniques: gleaning, where they pick insects from foliage, tree crevices, rocks, or the ground; sallying, where they fly out from a perch to capture an insect and return to the same or a different perch; and continuous aerial feeding, where they catch insects while in flight.
Birds that catch insects in the air often have more powerful flight muscles and larger, broader bills or wider gaping mouths compared to those that forage on the ground.
Molluscivorous birds primarily consume molluscs such as snails, slugs, squids, oysters, and mussels. Shorebirds, like oystercatchers, are well-known mollusc eaters. They have evolved strong jaws and long, curved bills that enable them to probe for prey in sand and mud.
The snail kite, a bird of prey found in the Americas, feeds almost exclusively on apple snails. However, when food is scarce, it may also consume other freshwater snails, crustaceans, and small turtles.
Ophiophagous birds are species that primarily feed on snakes. Only a few birds specialise in snake hunting, including the secretary bird, the red-tailed hawk, and the snake eagles (Circaetinae), a subfamily of Accipitridae. This group includes the crested serpent eagle, the brown snake eagle, and the Congo serpent eagle.
Snake-eating birds have sharp talons, exceptional vision, and rapid reflexes to aid in hunting, along with robust digestive systems to process their sizable prey. As well as these specialists, many other birds, including birds of prey, herons, corvids, and roadrunners, occasionally consume snakes.
Haematophagous birds are species that feed on blood. Examples include the sharp-beaked ground finch, commonly known as the vampire finch, the hood mockingbird, the Tristan thrush, and oxpeckers.
Blood is rich in proteins and lipids, providing a valuable food source that requires relatively little effort to obtain, especially useful when other food is scarce. Many blood-feeding birds also remove insects and parasites from their hosts while consuming blood, forming a mutualistic relationship.
Carrion, the decaying flesh of dead animals, is an important food source for many large birds. Vultures are the most well-known carrion eaters, having evolved exceptional adaptations for scavenging. They possess a keen sense of smell to locate carcasses, highly acidic stomachs to neutralise harmful bacteria, and specialised flesh-eating gut bacteria to aid digestion. Some scientists also believe their bald heads help keep them clean while feeding.
Other birds that consume carrion include corvids, gulls, skuas, turnstones, and various birds of prey.
