Defining bald eagle size
When it comes to assessing a bald eagle size, perception plays an important role. Naturally, we tend to assume that larger eagles are proportionally heavier than smaller ones.
While this is generally true, weight as the only measure of size can be unreliable. An eagle’s weight can be influenced by the time of the year, the temporary availability of food, and whether a bird had a large meal or not before being weighed.
To better understand the size of the bald eagle, I use weight (mass) and other less variable linear measures such as an eagle’s length and wingspan.
What is a bald eagle size? A bald eagle’s size varies with latitude and sex. Birds in the southern parts of the bald eagle’s range are smaller than those in the northern states and Alaska. Also, males are smaller than females. Across the eagle’s range and combining males and females, the bald eagle has an average weight of 9.1 lb, an average wingspan of 6 ft 7 in, and an average length of 2 ft 7 in.
Bald eagle’s weight
Bald eagles are unique in that their weight varies regionally. Eagles in lower latitudes, such as those in the southern states and northern Mexico, are smaller and lighter in weight than those in high latitudes such as the northern U.S. states, Canada, and Alaska.
In addition to the latitudinal or regional variation across its range, male bald eagles are smaller than females. Ornithologists have found that females bald eagles are generally 25% larger than males.
Such differences in the size of bald eagles in the south versus those in the north, plus females being larger than males, make it difficult to tell the size of the bald eagle. An approximation to America’s national bird’s size is an average number obtained from bald eagles in the south and another for those in the north.
|Southern Latitudes||Northern Latitudes|
|Bald Eagle’s Average Weight||3.27 kg (7.2 lb)||4.79 kg (10.7 lb)|
The weight of a bald eagle is taken from live birds and, as mentioned above, are subject to variation. Studies that included weighing live bald eagles found that a bird’s weight can vary as much as 5 to 10% during a day.
Bald Eagle Wingspan
The wingspan is also used as a measure of bird size. A bald eagle’s wingspan is the distance between the fully extended wingtips. The wingspan is a useful clue for assessing the size and identifying birds of prey soaring with their spread wings.
The wingspan is a measurement commonly provided in bird identification field guides for birds that soar and glide, such as vultures, storks, hawks, eagles, and other birds of prey.
Beware that it can be difficult to judge the length of a bird’s wingspan when you see one in the field. The tendency is to think that the birds have longer wingspans than what they really have.
A bald eagle’s wingspan is taken from specimens collected for scientific collections before being prepared as a museum specimen. The fresh specimen is laid on its flattened back, and its wings spread to obtain the distance between wingtips.
The following table shows measurements of bald eagle Wingspans in various units.
|Range||71 – 91 in||5.9 – 7.6 ft||180 – 231.6 cm||1.8 – 2.3 mt|
|Average||81 in||6.7 ft||202.2 cm||2 mt|
Lear more about the bald eagle wingspan.
Bald Eagle’s Length
A bald eagle’s length is the distance between the tip of a bird’s bill and its tail tip. A bird’s length is commonly given in bird identification field guides to illustrate the approximate size.
Some use length to indicate a bald eagle’s height.
A bird’s length is taken from birds collected for scientific collections before being prepared as a museum specimen. The fresh specimen is laid on its gently flattened back to measure the distance between the bill’s tip and the tail tip.
While the length of a bald eagle provides a reference to assess its size, beware that it can be difficult to judge an individual’s size based on its known length. A perched bird adopts many positions, most of which is not having its neck stretched out.
The following table shows measurements of bald eagle length in various units.
|Range||27.9 – 37.8 in||2.3 – 3.15 ft||70 – 96.3 cm||0.7 – 0.6 mt|
|Average||33 in||2.7 ft||83.1 cm||0.65 mt|
Bald eagle size versus osprey versus red-tailed hawk
A good way to illustrate the size of a bald eagle is to compare it to familiar birds. Ospreys and red-tailed hawks are common birds of prey likely to be found in bald eagle habitat and even soaring alongside. Birds of similar or even longer wingspans include golden eagles (80 in), California condors (109 in), and white pelicans (108 in).
Bald Eagle Next to Human
A bald eagle’s wingspan ranges from 5 ft 9 in smaller males to 7 ft 6 in larger females with an average wingspan of 6 ft 7. The bald eagle’s average wingspan, positioned next to an adult human male of an average height of 5 ft 9 in, is “taller” by approximately 8 in.
Some of the larger female bald eagles can have wingspans of up to 7 ft 6 in. This means that larger eagles can have wingspans of up to 1 ft 7 in “taller” than a man of average height. That is nearly 2 ft taller than a standing man!
The bald eagle size is so variable across its range that it is difficult to give a single number to indicate its size. Instead, this article shows the weight (mass) and linear measures such as wingspan and length as size measures. The bald eagle is compared with common birds of prey, such as osprey and red-tailed hawk, to understand size and proportions. Finally, an adult bald eagle is compared with an adult human of average height.
- Buehler, D. A. (2000). Bald Eagle (Haliaeetus leucocephalus), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
- McCollough, M. A. (1989). Molting sequence and aging of Bald Eagles. Wilson Bulletin 101:1-10.
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