The most significant factor in distinguishing male and female martial eagles is their size, with females being larger than males. Experienced observers can also identify the sex of lone birds in the wild by the females’ more robust feet and longer tarsi.
Size Differences Between Male and Female Martial Eagles
When it comes to size, there are clear distinctions between male and female martial eagles:
| Measurement | Male Martial Eagles | Female Martial Eagles |
|---|---|---|
| Wing Chord | 560 to 610 mm (22 to 24 in) | 605 to 675 mm (23.8 to 26.6 in) |
| Tail Length | 273 to 280 mm (10.7 to 11.0 in) | 280 to 320 mm (11 to 13 in) |
| Tarsus Length | 97 to 118 mm (3.8 to 4.6 in) | 114 to 130 mm (4.5 to 5.1 in) |
The larger size of female martial eagles, including their more robust feet and longer tarsi, can help experienced observers distinguish the sex of lone birds in the wild.
Plumage Differences Between Male and Female Martial Eagles
Image source: Martial eagle by Charles J. Sharp
While size is the primary distinguishing factor, there are also some differences in the plumage of male and female martial eagles:
Adult Plumage
Adult martial eagles, regardless of sex, have dark brown upperparts, head, and upper chest, with dark feathers that can appear grayish, blackish, or even plum-colored depending on lighting conditions. The body underparts are feathered white with sparse but conspicuous blackish-brown spotting. The underwing coverts are dark brown, with the remiges being pale streaked with black, overall imparting the wings of adults a dark look. The underside of the tail has similar barring as the remiges while the upperside is the same uniform brown as the back. The eyes of mature martial eagles are rich yellow, while the cere and large feet are pale greenish, and the talons are black.
Juvenile Plumage
Juvenile martial eagles, on the other hand, have a distinct plumage. They have a pearly gray color above with considerable white edging, as well as a speckled grey effect on the crown and hind neck. The entire underside is conspicuously white, with the wing coverts of juveniles being mottled grey-brown and white, and patterns of bars on primaries and tail that are similar to adults but lighter and greyer.
Behavioral Differences Between Male and Female Martial Eagles
In addition to physical differences, there may also be some behavioral differences between male and female martial eagles, though these are less pronounced and more difficult to observe in the wild. Females are generally more aggressive and territorial, particularly during the breeding season, while males may be more involved in courtship displays and nest-building activities.
Conclusion
Distinguishing between male and female martial eagles primarily comes down to size, with females being significantly larger than males. Experienced observers can also use the more robust feet and longer tarsi of females to identify the sex of lone birds in the wild. While there are some plumage differences, these are more subtle and can be influenced by factors like lighting conditions. Understanding these key differences can help birdwatchers and researchers better understand the ecology and behavior of this impressive raptor species.
