The Golden Eagle (Aquila chrysaetos) is one of the most powerful and widely distributed birds of prey in the Northern Hemisphere. This raptor is known for its impressive size and strength, which it utilizes as a hunter across diverse open landscapes, from mountainous regions to deserts and tundra. Examining the weight of this species provides a direct insight into the physical demands of its predatory lifestyle.
Defining the Golden Eagle’s Mass
The mass of an adult Golden Eagle typically falls within a broad range, reflecting individual variation and environmental factors. Generally, an adult Golden Eagle weighs between 3.0 and 6.7 kilograms (6.6 to 14.8 pounds). Across the entire species, the average weight is cited around 4.4 kilograms (9.7 pounds).
The eagle’s weight fluctuates based on recent feeding success, with a successful hunt adding significant mass. Researchers studying wild eagles have also observed weight changes in individuals over the course of the year.
These avian predators experience seasonal weight fluctuations, often weighing more during colder winter months due to increased fat stores for insulation and energy. Conversely, weight decreases during the breeding season due to the high energy expenditure of nesting, incubation, and provisioning young.
Understanding Size Variation Between Sexes and Regions
The wide weight range observed in Golden Eagles is largely explained by sexual dimorphism and geographic variation. Like many raptors, females are noticeably larger and heavier than males, exhibiting reverse sexual dimorphism.
Female Golden Eagles typically weigh 10 to 25% more than their male counterparts. The average female mass is around 5.1 kilograms (11 pounds), while males average closer to 3.6 kilograms (7.9 pounds). This size disparity means that the heaviest males can overlap with the lightest females.
Geographic location and climate also influence the average weight of local populations, a pattern consistent with Bergmann’s Rule. Eagles inhabiting colder, northern regions tend to be larger and heavier than those found closer to the equator. For example, the largest subspecies, A. c. daphanea, has females that can reach 6.35 kilograms (14.0 pounds), while the smallest subspecies, A. c. japonica in Japan, has females averaging 3.25 kilograms (7.2 pounds).
Wingspan and Body Length: A Full Picture
The eagle’s weight is directly supported by its large physical dimensions: its wingspan and body length. An adult Golden Eagle measures between 70 and 84 centimeters (27.6 to 33.1 inches).
The impressive wingspan commonly stretches between 1.8 and 2.34 meters (5 feet 11 inches to 7 feet 8 inches). This expansive wing structure allows the bird to efficiently soar and glide on thermal updrafts, conserving energy while scanning vast territories for prey.
This combination of significant mass and broad wingspan contributes to the eagle’s ability to hunt and carry prey. Golden Eagles are known to carry prey items that weigh up to 3 to 4 pounds during flight, a feat enabled by their powerful feet and large talons. Their size allows them to target a variety of prey, ranging from small ground squirrels and rabbits to larger mammals like marmots.