Eagles are recognized as apex predators, occupying the top of the food chain. Due to their size, powerful talons, and mastery of flight, adult eagles have virtually no consistent natural predators. Predation is overwhelmingly concentrated on the younger stages of an eagle’s life, specifically from egg to fledgling. Mortality due to other animals primarily occurs when the young bird is defenseless in the nest or inexperienced outside of it.
Predation on Eggs and Nestlings
The egg and nestling stage represents the period of highest vulnerability for eagles, as they are stationary and entirely dependent on parental defense. Nests, though often massive and built high in tall trees or on cliffs, are still accessible to several groups of determined predators. The primary deterrent to a successful raid is the presence of one or both adult eagles, who vigorously guard the nest site.
Mammalian carnivores are a major threat, particularly those adept at climbing to the nest site. Raccoons are among the most common mammalian nest predators, capable of reaching high nests to consume eggs and small chicks. Black bears are nimble climbers that occasionally raid nests, drawn by the scent of the eggs or young birds.
Avian predators also pose a danger, often exploiting a temporary absence of the parent birds. The Great Horned Owl is a significant threat, known to take eggs and chicks and sometimes displace the eagles entirely to take over a nest. Other opportunistic birds like ravens and magpies target eggs and newly hatched chicks, using their sharp beaks to penetrate the shell or soft bodies.
Threats to Juvenile and Fledgling Eagles
The period after an eagle leaves the nest, known as the fledgling or juvenile stage, remains dangerous until the bird achieves full size and hunting proficiency around four to five years of age. Mortality rates for young eagles during their first year can be high, as they are clumsy fliers and inexperienced hunters. These young birds frequently spend time on the ground or in low branches, making them susceptible to terrestrial predators.
Larger mammalian carnivores present a direct danger to the exposed juvenile, which lacks the speed and aerial dominance of a mature eagle. Coyotes, bobcats, and wolves may opportunistically attack a fledgling encountered on the ground or while it is feeding on carrion. Bears will also attack flightless chicks or juveniles that have not yet mastered flight.
Avian competition also poses a threat, including territorial attacks from larger raptors. The Great Horned Owl remains a formidable aerial opponent due to its nocturnal hunting advantage and ability to strike from above. Other mature eagles, especially non-parental adults, may attack juveniles during territorial disputes or to eliminate competition for resources, which is a form of infanticide.
Predation Scenarios for Mature Eagles
Predation on a healthy, mature eagle is rare, as the adult bird is a powerful, highly mobile predator with few equals in its environment. When it occurs, it is typically an opportunistic attack based on a specific vulnerability rather than a routine hunting interaction. An eagle becomes susceptible to predation if it is injured, sick, or otherwise incapacitated, such as from a fall or a fight.
In such cases, the bird may be attacked by large terrestrial carnivores that would otherwise avoid confrontation, including bears, wolves, or cougars. These predators may also engage an eagle when it is grounded and feeding on a large carcass, where conflict over the food source can quickly turn fatal. Eagles are sometimes killed in intense territorial battles with other large raptors, such as other eagles or powerful owls.