The act of birds eating other birds, known as avivory, is a widespread and natural occurrence within the avian food web. This specialized diet is found across a diverse range of species, encompassing large birds of prey and smaller, opportunistic hunters that target adults or their young. Avian predators, or avivores, often possess specific physical adaptations, such as strong talons and hooked beaks, suited for catching and subduing feathered prey. The presence of these predators shapes the behavior and ecology of countless other species, making avivory a fundamental component of ecosystem health.
Specialized Hunters: Raptors and Owls
The birds most highly adapted for pursuing and capturing other birds in flight are the diurnal raptors, specifically the Accipiters and Falcons. Accipiters, such as the Cooper’s Hawk, possess short, rounded wings and a long tail, suited for navigating dense woodland environments. These hawks employ an ambush strategy, hunting from a concealed perch and launching into a burst of speed to chase down songbirds through trees and brush. They use their long toes and sharp talons to seize and subdue their prey.
Falcons, like the Peregrine Falcon, specialize in open-air hunting and are known for their speed. The Peregrine primarily uses a hunting technique called a “stoop,” diving from a great height to strike a flying bird with a closed foot at tremendous velocity. This high-speed attack ensures the mid-air impact is sufficient to stun or kill the prey immediately.
Nocturnal avivores include species like the Great Horned Owl, which uses silent flight and acute hearing to hunt birds while they are roosting. All birds of prey share common physical traits, including a hooked beak for tearing flesh and powerful talons for grasping. The females in bird-eating raptor species are often noticeably larger than the males, a phenomenon called reversed sexual dimorphism that may enhance their hunting success.
The Opportunistic and Unexpected Avian Predators
Avivory is not restricted to traditional raptors, as many other bird groups opportunistically prey on other birds, often employing specialized behaviors. Shrikes, sometimes called “butcherbirds,” are passerines that hunt like raptors but lack strong talons. To compensate, shrikes impale their prey—which can include small vertebrates and birds—on sharp objects such as thorns or barbed wire. This impaling behavior creates a food cache, or larder, allowing the bird to dismember and consume the prey later. For males, a large cache also functions as a display of hunting prowess to attract potential mates. Shrikes kill larger prey by grasping the neck with their hooked beak and shaking the victim vigorously to damage the spinal column.
Gulls and terns, particularly the larger species, are opportunistic avivores that prey on other seabirds. These gulls frequently target the eggs, chicks, and fledglings of smaller colonial birds, but they will also take adults. Some individual gulls develop a specialization for preying on a single type of bird, which can have significant localized impacts on the prey species’ nesting success. Finally, wading birds like Great Blue Herons consume the young of aquatic birds, such as ducklings, which they spear or seize with their long, pointed bills.
Targeting the Vulnerable: Predation on Eggs and Nestlings
Predation risk is high for eggs and young birds, which are immobile and confined to a nest site, a vulnerability that many generalist predators exploit. Corvids, the family that includes crows, ravens, and jays, are widespread nest predators. They use their intelligence to search for and raid the nests of smaller birds, often consuming the eggs or newly hatched nestlings. Corvid predation is a significant cause of nest failure for many open-nesting songbirds, and their presence can be influenced by human-provided resources in urban and suburban areas. Beyond corvids, smaller birds, such as House Sparrows, sometimes engage in intraspecific predation by killing the young of competing species to eliminate rivals.
Avian Predation in the Ecosystem
The consumption of one bird by another contributes to the stability and evolution of the entire avian community. By removing the sick, weak, or less fit individuals from a population, avivory helps maintain the overall health and vigor of prey species. This constant pressure drives natural selection, encouraging the evolution of traits like better camouflage, more secure nesting site choices, or faster escape responses in prey populations.
Predation by avivores also influences the structure of entire ecological communities. The perceived risk of an attack can alter the habitat selection and foraging behaviors of other birds. For example, the presence of a predator may cause prey species to avoid certain areas, leading to a shift in the composition of the local bird community. This web of interactions demonstrates that avian predation shapes the diversity and resilience of bird populations globally.