Eagles are apex avian predators, classified as raptors, whose existence is entirely dependent upon a diet of animal protein. As obligate carnivores, eagles do not eat fruit, vegetables, or any significant plant matter. Their biology, from external hunting tools to internal digestive processes, is specialized for locating, capturing, and processing flesh. This specialization dictates where they live and how they interact with their environment.
Primary Prey and Dietary Range
The diet of an eagle is varied, with specific prey preferences differing between species. Bald Eagles are categorized as “fish eagles” due to their preference for fish, which they snatch from the water’s surface near lakes, rivers, and coastlines. Their habitat selection is tied to the availability of this aquatic food source, and they also consume waterfowl, such as ducks and gulls, when fish are less abundant.
Golden Eagles are predators of open country and mountains, focusing on terrestrial prey. Their diet is dominated by small-to-medium-sized mammals, including rabbits, hares, marmots, and ground squirrels. These powerful hunters occasionally hunt cooperatively to bring down larger animals like young deer or antelope.
Both species supplement their diet by scavenging carrion, especially during winter months when live prey is scarce. Eagles are also notorious for kleptoparasitism, aggressively stealing food from other birds, such as ospreys. The diet is consistently high in protein and fat, with any incidental plant material being undigested contents from the stomach of their herbivorous prey.
Specialized Tools for Hunting
The eagle’s success relies on physical adaptations engineered for predation. Their vision is their most sophisticated tool, possessing an acuity up to seven times sharper than that of a human. This allows an eagle to spot a small mammal from several miles away while soaring. This capability is enhanced by having two foveae in each eye for simultaneous forward and lateral focus.
Once prey is located, the eagle employs its powerful feet and talons to secure the kill. Each foot is equipped with four sharp claws that can exert a crushing pressure estimated to be around 400 pounds per square inch at the tips. The feet function as a lethal grasping mechanism, designed to incapacitate or kill prey instantly upon impact.
Following the capture, the eagle uses its heavy, hooked beak, which is designed for tearing and shearing, not chewing. The curved shape and sharp edges of the beak allow the bird to efficiently rip flesh and muscle into pieces small enough to swallow.
The Physiology of Obligate Carnivory
The internal anatomy of an eagle confirms its commitment to a flesh-based diet, as its digestive tract is streamlined for rapid protein and fat breakdown. Food first passes into the crop, a temporary pouch in the esophagus that allows the eagle to store large quantities of food. This storage capacity enables the bird to gorge when prey is available and survive through periods of scarcity.
Digestion begins in the proventriculus, the glandular stomach, which secretes powerful digestive juices, including hydrochloric acid and the enzyme pepsin. The acid concentration in raptors is remarkably strong, capable of dissolving bone to extract calcium and other nutrients. This high acidity is a direct adaptation for managing a diet heavy in bone and whole prey.
The food then moves to the gizzard, or ventriculus, which is a muscular stomach that mechanically grinds the contents. Since meat is easy to break down, the eagle’s gizzard is less muscular than that of a grain-eating bird. Indigestible components of the meal, such as fur, feathers, scales, and small bone fragments, are compressed into a dense pellet. This pellet is then regurgitated, eliminating materials the eagle’s system cannot process, confirming that complex plant cellulose is not a viable nutrition source.