Just How Big and Powerful is the Harpy Eagle?

This article compares the Harpy Eagle’s weight, length, and wingspan with those of the world’s top three largest eagles to answer this question.

How big is the Harpy Eagle?  Using body mass, length, and wingspan as metrics of size, the Harpy Eagle, is the world’s heaviest and longest eagle. In the wingspan category, though, the Harpy Eagle falls to fourth place among the world’s largest eagles. The Harpy Eagle has short and round wings, suitable for life inside dense tropical forests where it has to maneuver through dense vegetation. The Harpy Eagle does not regularly soar.

Table Of Contents

Female Harpy Eagle is the the world's largest eagle.
Female Harpy Eagle. Photo: Fernando Serna Agudelo.

The Harpy Eagle Female is Larger than the Male.

In most birds, the male is larger than the female. But in some birds of prey, the female can be half as heavy as the male.

The reason for such size disparity between sexes has not been determined with certainty. Some ideas that may help explain such difference include:

Some ornithologists propose that the difference in size among raptors allows them to hunt prey of different sizes, therefore not competing for the same prey.

  • To avoid competition between sexes. Some ornithologists propose that the difference in size among raptors allows them to hunt prey of different sizes, therefore not competing for the same prey.

    The smaller male can hunt smaller and faster-moving prey while the female is better equipped to prey upon larger but less agile prey. Body size is then regarded as a measure of power and strength.
  • Different roles of males and females during breeding. The female Harpy Eagle does most of the incubation and stays on the nest during the first months after the egg hatches, protecting the young chick. During this period, the male provides food for the female and the growing chick in the nest. The larger female can protect the eggs and chicks, even from large predators such as monkeys.

    Because there is a greater amount of smaller prey in nature, the smaller male may be better equipped to consistently hunt and feed the female and chick in the nest.
  • Protection against aggressive males. Male Harpy Eagles have a reputation of having sudden bursts of aggression towards females. It is believed that the female Harpy Eagle chooses small males to make sure she can protect herself, the egg, or chick from the attack of smaller but aggressive males.

Measurements of male and female Harpy Eagle. (See sources below)

The following table shows the weight, length, and wingspan of the male and female Harpy Eagle. Mesurements used to compare the Harpy Eagle with other eagles are:

WeightFemale: Average: 8.3 kg (18.2 lb)

Length Male and Female: Average: 96.7 cm (32.3″)

Wingspan: Male and Female: Average: 203.5 cm (67.8″)

WeightMale
Range: 4-4.8 Kg (8.8-10.6 lb)
Average: 4.4 kg (9.7 lb)
Maximum: 4.8 kg (10.6 lb)

Length Male and Female
Range: 86.5-107 cm (28.8-35.6 lb)
Average: 96.7 cm (32.3″)
Maximum: 107 cm (35.6″)

Wingspan: Male and Female
Range: 183-224 cm (61-74.6″)
Average: 203.5 cm (67.8″)
Maximum: 224 cm (74.6″)

WeightFemale
Range: 7.6-9 Kg (16.7-19.8 lb)
Average: 8.3 kg (18.2 lb)
Maximum: 9 kg (19.8 lb)

Comparing Eagle Measurements

Comparing bird measurements can be tricky. Measurements vary between sex, age, and just between individuals of the same species.

When it comes to comparing weight, the variation in measurements can be even greater. A bird’s weight can vary throughout the year and even the time of the day.

Added to the inherent individual variation among bird measurements is the fact that biologists in the field can obtain these metrics differently.

Variations in these metrics can make a comparison between eagle species less reliable. Accurate measurements are particularly important when comparing species of eagles of somewhat similar sizes.

Another source of error is that measures taken in the field are compared to measurements of birds kept in captivity. It is well established that captive birds are heavier than wild birds.

Steller's Eagle the second largest eagle.
Steller’s Sea Eagle. Photo: Sascha-Wenninger/Flickr/CC by 2.0

Understanding Eagle Weight, Length, and Wingspan.

Length, Weight, and Wingspan are rough indicators or size. These metrics are difficult to obtain and are rarely used in scientific studies.

  • Weight: The weights or body mass of an eagle is obtained from live birds. As with the other measurements, weight can have a good deal of variation. Studies have shown that a bird’s weight can vary as much as 5 to 10% during a day.
  • Length:  The length of an eagle is the distance between the bill’s tip and the tip of the tail. It is obtained from dead museum specimens by laying the bird on its back and flattening out the head and neck gently. The length of an eagle is prone to error and is rarely used for any comparative study.
  • Wingspan: An eagle’s wingspan is the distance between the wingtips when the wings are held outstretched.  This measurement is obtained from live or dead birds before being prepared as museum specimens. The wingspan is used only as a rough estimation of size.

The Harpy Eagle’s Metrics Relative to other Eagles.

Body Weight

The Harpy Eagle is the world’s heaviest eagle, followed closely by the Steller’s Sea Eagle. In a more distant third place comes the Philippine Eagle.

When it comes to strength and power, the female Harpy Eagle is in a league of her own.

 The female Harpy Eagle regularly hunts for sloths, monkeys, and other medium-sized arboreal mammals. Females Harpy Eagles have been reported to attack monkeys in the canopy, followed by a struggle as both the eagle and prey fall and fight on the ground.

The average prey size of a Harpy Eagle prey is 5.3 kg (11.6 lb).

The similarly heavy female Steller’s Sea Eagle feed mainly on dead or live fish, especially Pacific salmon, and to a lesser extent, carcasses found near the coastline.

The average length and weight of the Pacific Salmon are 40.6 cm (16″) and 1.8 kg (lb), respectively.                      

On rare occasions, Steller’s Sea Eagles have been observed killing small birds that are injured or unable to fly. Overall, the Steller’s Sea Eagle does not use its size as a tool to subdue its prey.

The Philippine Eagle comes in third place. Like the Harpy Eagle, the magnificent Philippine Eagle also lives in dense tropical forests and hunt arboreal mammals, but its average prey size is smaller.

The Philippine Eagle hunts mostly Flying Lemurs and Palm Civets and, to a lesser extent, small monkeys, squirrels, bats, and rats.

The average prey size of a Philippine Eagle is 2.3 kg (5.1 lb).

The Harpy Eagle is the world’s heaviest and most powerful eagle by body weight and by the fact that it hunts larger prey items.

Philippine Eagle
Philippine Eagle. Photo: The-Wandering-Angel/Flickr/CC by 2.0

Top Three Eagle Species: Body Weight.

1. Harpy Eagle

Female
Maximum: 9 kg (19.8 lb)
Average: 8.3 kg (18.2 lb)
Range: 7.6-9 Kg (16.7-19.8 lb)

Male
Maximum: 4.8 kg (10.5 lb)
Average: 4.4 kg (9.7 lb)
Range: 4-4.8 Kg (8.8-10.5 lb)

2. Steller’s Sea Eagle

Female
Maximum: 9 kg (19.8 lb)
Average: 7.9 kg (17.4 lb)
Range: 6.8-9 kg (15-19.8 lb)

Male
Maximum: 6 kg (13.2 lb)
Average: 5.45 Kg (12 lb)
Range: 4.9-6 kg (10.8-12.2 lb)

2. Philippine Eagle

Male and Female
Maximum: 8 kg (17.6 lb)
Average: 6.4 kg   (14.1 lb)
Range: 4.7-8 kg    (10.3-17.6 lb)

White-tailed Eagle. Photo: Andreas Weith/Flickr/CC by 2.0

Length

Most field guides provide the length of a bird as an indicator of size.

With 42.2″ from tip to tail, the Harpy Eagle is the world’s largest eagle followed very closely by the Steller’s Sea Eagle with 41.3″.  Given the small difference in length between these two eagles, the Harpy Eagle and the Steller’s Sea Eagle are practically tied in the first place.

Australia’s largest bird of prey, the Wedge-tailed Eagle, comes in third place. The Wedge-tailed Eagle has a total length of (41″) but weighs only (3 kg). This eagle’s long neck and tail are the reasons it is categorized as one of the three top longest eagles.

Using an eagle’s length as an approximate estimation of size can be challenging. A perched eagle preening itself with the feathers fluffed in a relaxed posture may appear bulkier but shorter. The same eagle getting ready to take off with the neck stretched and its feathers close to its body may give the impression of a long and slender bird.

The key to judging an eagle’s length in the field is to watch it for several minutes, so the bird shows more than one posture and provides a better idea of its actual length.

Top Three Eagle Species: Length.

1. Harpy Eagle

Male and Female
Maximum: 107 cm (42.2 in)
Average: 96.7 cm (38.1 in)
Range: 86.5-107 cm  (34-42.1 in)

2. Steller’s Sea Eagle

Female
Maximum: 105 cm (41.3 in)
Average: 95 cm (37.4 in)
Range: 85–105 cm (33.4-41.3 in)

2. Wedge-tailed Eagle

Female
Maximum: 104 cm  (41 in)
Average: 92.5 cm  (36.4 in)
Range: 81–104 cm  (31.8-41 in)

Wedge-tailed Eagle. Photo: Chris/Flickr/CC by 2.0

Wingspan

With 254 cm wide, the Steller’s Sea Eagle has the longest wingspan, followed by the White-tailed Eagle (244 cm) and the Wedge-tailed Eagle (232 cm).

The Harpy Eagle comes in fourth place in the wingspan category.

The wingspan of an eagle is correlated to the wing function and the environments where an eagle lives. Steller’s Sea Eagle, White-tailed Eagle, and Wedge-tailed Eagle soar and glide in the open habitats they live. These eagles’ wings are long and narrow, suited for soaring, gliding, and fast-flying in open spaces.

Conversely, the Harpy Eagle does not soar but spends its entire life in the canopy and subcanopy of dense tropical forests. The Harpy eagle generally sits and waits motionless, waiting for the right time to launch an attack on an unassuming prey.

A burst of fast flight maneuvering through dense forest requires short and rounded wings.

The Philippine Eagle lives in similar tropical forests and uses a similar hunting technique. The Philippine Eagle has short and rounded wings the bird uses for a similar hunting strategy.

Top Three Eagle Species: Wingspan.

1. Steller’s Sea Eagle

Male and Female
Maximum: 245 cm (96 in)
Average: 220 cm (86.6 in)
Range: 195–245 cm (76.7-96.4 in)

2. White-tailed Eagle

Male and Female
Maximum: 244 cm (96 in)
Average: 218.5 cm (86 in)
Range: 193–244 cm (76-96 in)

3. Wedge-tailed Eagle

Male and Female
Maximum: 232 cm (91.3 in)
Average: 207 cm (81.4 in)
Range: 182–232 cm (71.6-91.3 in)

Conclusions

The Harpy Eagle is indeed the heaviest, longest, and more powerful eagle in extant.

The now extinct Haast’s Eagle of New Zealand was the largest eagle to ever live. It was almost twice as big as the Harpy Eagle with a bodyweight of approximately 15 kg (lb). The Haast’s Eagle hunted large flightless moas and other large prey, making the eagles large as an evolutionary response.

Do you agree with this analysis of the largest and most powerful eagle?

Do you have any experience with a Harpy Eagle?

References:

  • Brazil, M. (1993). The world’s most spectacular raptor – Steller’s Sea Eagle. Birding World. 6(1): 28-31.
  • Ferguson-Lees, J., and D. A. Christie (2001). Raptors of the World. Christopher Helm, London, UK. Brazil, M. (1993). The world’s most spectacular raptor – Steller’s Sea Eagle. Birding World. 6(1): 28-31.
  • Fowler, J.M., and Cope, J.B. (1964). Notes on the Harpy Eagle in British Guiana. Auk. 81(3): 257–273.
  • Howell, S. N. G., and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford, United Kingdom.
  • Schulenberg, T. S. (2020). Harpy Eagle (Harpia harpyja), version 1.0. In Birds of the World (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. 

5 thoughts on “Just How Big and Powerful is the Harpy Eagle?”

  1. Peter van Holland

    Hi, very interesting topic and information, thank you. I was wondering where the African Martial eagle (Polemaetus bellicosus) is in all of this. I’ve read things about attacking and killing small antelopes, warthogs. In terms of power it should be right there. Like the African crowned eagle (Stephanoaetus coronatus) not mentioned once. Do you have good information about the true power of the harpy eagle? I have heard that with with feet/claw they have an amount of pressure equal to that of a Rottweiler (dog breed) bite.
    Hope to hear from you. Cheers, Peter.

    1. Hi Peter,

      This comparison used bodyweight as a metric to compare the top 3 heaviest eagles.
      The Harpy Eagle is indeed the heaviest of the three, although the difference in body weight is rather small. I point out how variable the bodyweight of these eagles can be to caution the readers.

      The Harpy Eagle is indeed the most powerful of the top largest eagles as the Steller’s Sea Eagle and White-tailed Eagle are fish-eating and opportunistic carrion feeding eagles.

      You raise a good point when you bring up the Martial and Crowned Eagles. These eagles are rather powerful. They hunt large prey as well. But they are smaller. The Martial and Crowned Eagles weight 3.06 kg and 3.4 kg, respectively, on average.

      To compare power among eagles that hunt live prey, perhaps one would need to use the ratio of eagle’s body weight to the average weight of the prey they regularly take. The even smaller but aggressive (and powerful?) Hawk-Eagles of the tropics come to mind.

      Thanks for stopping by!

  2. 1st Philippine Eagle – Largest eagle in total physical dimensions. Tallest max recorded 112 cm its ave height is equals to the maximum recorded for Harpy and Stellers Sea Eagle, largest wing surface area. Note: Not the heaviest eagle. Factoring the weight on average it ranks second to Stellers Sea Eagle

    Source:
    Wikipedia, Animal Diversity Web – Michigan University, BBC Arkive Image of Life on Earth, World Atlas, Philippine Eagle Foundation, WWF World Wildlife Fund, Chicago Field Museum, Cornell Lab of Ornitology).

    Notable people who study Philippine Eagle and prove the conclusion.
    Emmy Award Winning Documentarist Neil Rettig, Former BBC Manager and Naturalist Sir David Attenborough, Famous American Aviator Charles Augustus Lindbergh, Norita Scott-Pezett of Audubon-Panama Harpy Eagle Foundation, a BirdLife International Global Council member (1999-2004), Dr. Robert Kennedy at the Harvard University Museum of Natural History in Boston. (Dr. Kennedy is the principal author of the book A Guide to the Birds of the Philippines. He has extensively studied the Haring Ibon with excellent video documentation, and Blas Blas Tabaranza Jr. is Director of the Terrestrial Ecosystems Program of the Haribon Foundation. He is a Professor of Zoology at the Mindanao State University-Iligan Institute of Technology with extensive field experience in ornithology and mammalogy.

    2nd Harpy Eagle – Smaller in lenght, total size than the Philippine Eagle but robust in built with largest talon size of all eagles in the world.Experiment done in Chicago Field Museum The Philippine Eagle tops in 5 of the 7 external measurements, namely, total length, bill gape, culmen, bill height and tarsus. The Harpy tops in 1 out of 7 measurements, namely the talon.

    Note not the tallest nor the heaviest Eagle in the world.

    3rd Stellers Sea Eagle – Its the worlds heaviest Eagle on average but often lags behind the Philippine Eagle and Harpy Eagle in some other measurements.

    4th White Tailed Sea Eagle – Its the largest eagle in Europe and ranks 4th in overall ranking when in terms of size and weight. This Eagle has the longest wingspan on average of all the Eagles in the World.

    5th Martial Eagle – Largest Eagle of the African Continent. In overall ranking it beats the black eagle, bald eagle, golden eagle and wedge tailed eagle in total size and weight.

    Conclusion:
    In terms of total size the largest is Philippine Eagle.

    In terms of weight means heaviest goes to Stellers Sea Eagle.

    Harpy Eagle is the most robust built eagle a reason why most people claimed it as the most powerful eagle in the world.Its talin size is comparable to a Grizzly Bear Claw. Although Philippine Eagle has the most impressive prey records among the three giant eagles, Harpy is the one to beat.

    If you put all three Eagles in one cage namely Philippine Eagle, Harpy Eagle and Stellers Sea Eagle . By looking them obviously the Philippine Eagle is the largest since it is the largest in Physical Dimensions.

  3. 1st Philippine Eagle – Largest eagle in total physical dimensions. Tallest max recorded 112 cm its ave height is equals to the maximum recorded for Harpy and Stellers Sea Eagle, largest wing surface area. Note: Not the heaviest eagle. Factoring the weight on average it ranks second to Stellers Sea Eagle

    Source:
    Wikipedia, Animal Diversity Web – Michigan University, BBC Arkive Image of Life on Earth, World Atlas, Philippine Eagle Foundation, WWF World Wildlife Fund, Chicago Field Museum, Cornell Lab of Ornitology, National Geographic, Animal Planet).

    Notable people who study Philippine Eagle and prove the conclusion.
    Emmy Award Winning Documentarist Neil Rettig, Former BBC Manager and Naturalist Sir David Attenborough, Famous American Aviator Charles Augustus Lindbergh, Norita Scott-Pezett of Audubon-Panama Harpy Eagle Foundation, a BirdLife International Global Council member (1999-2004), Dr. Robert Kennedy at the Harvard University Museum of Natural History in Boston. (Dr. Kennedy is the principal author of the book A Guide to the Birds of the Philippines. He has extensively studied the Haring Ibon with excellent video documentation, and Blas Blas Tabaranza Jr. is Director of the Terrestrial Ecosystems Program of the Haribon Foundation. He is a Professor of Zoology at the Mindanao State University-Iligan Institute of Technology with extensive field experience in ornithology and mammalogy.

    2nd Harpy Eagle – Smaller in lenght, total size than the Philippine Eagle but robust in built with largest talon size of all eagles in the world.Experiment done in Chicago Field Museum The Philippine Eagle tops in 5 of the 7 external measurements, namely, total length, bill gape, culmen, bill height and tarsus. The Harpy tops in 1 out of 7 measurements, namely the talon.

    Note not the tallest nor the heaviest Eagle in the world.

    3rd Stellers Sea Eagle – Its the worlds heaviest Eagle on average but often lags behind the Philippine Eagle and Harpy Eagle in some other measurements.

    4th White Tailed Sea Eagle – Its the largest eagle in Europe and ranks 4th in overall ranking when in terms of size and weight. This Eagle has the longest wingspan on average of all the Eagles in the World.

    5th Martial Eagle – Largest Eagle of the African Continent. In overall ranking it beats the black eagle, bald eagle, golden eagle and wedge tailed eagle in total size and weight.

    Conclusion:
    In terms of total size the largest is Philippine Eagle.

    In terms of weight means heaviest goes to Stellers Sea Eagle.

    Harpy Eagle is the most robust built eagle a reason why most people claimed it as the most powerful eagle in the world.Its talin size is comparable to a Grizzly Bear Claw. Although Philippine Eagle has the most impressive prey records among the three giant eagles, Harpy is the one to beat.

    If you put all three Eagles in one cage namely Philippine Eagle, Harpy Eagle and Stellers Sea Eagle . By looking them obviously the Philippine Eagle is the largest since it is the largest in Physical Dimensions.

  4. Largest Prey

    The wild animal known to have been killed and carried away by a bird was a 15 pound male red howler monkey killed by a harpy eagle (Harpia harpyja) in Manu National Park, Peru in 1990.

    An incredible video of a Golden Eagle taking a small Mountain sheep or goat and carrying it off to it’s nest. http://www.youtube.com/watch?v=4irYqe5yjcE

    The largest documented prey taken by a Philippine eagle is a 14 kg (30.8 lbs) Philippine deer Cervus at a nest studied by Kennedy in 1985. also on records; a mature female monkey taken and carrying it in one foot in Cagayan; and a large python.

    The African crowned eagle is Africa’s most powerful and ferocious eagle in terms of the weight and nature of prey taken. Mammalian prey, especially duikers, may weigh up to 34 kg (75 lbs) and still be preyed on by these Eagles.

Comments are closed.