Differentiating between male and female bald eagles can be a difficult undertaking because neither has any immediately obvious telltale gender markings. There are, however, multiple telling, albeit subtle, differences.
Female bald eagles are larger than their male counterparts by roughly a third in size. Females tend to have a body length of 35 to 37 inches, while males tend to be 30 to 34 inches long.
Both male and female eagles have four talons–three in front and one in back. The back-facing talon or hallux tends to be longer on female bald eagles.
The width from the top of the beak to the eagle's chin is the depth of the beak. Female bald eagles generally have deeper beaks than male eagles.
The female bald eagle will often have a lower voice than her mate. Gender may be determined by comparing the pitch of two eagles.
Gender Identification in Young Eagles
In a scientific study titled "Criteria for Determing Age and Sex of Nestling Bald Eagles," Dr. Gary Bortolotti determined that the difference between male and female bald eagle nestlings wasn't readily apparent until around 20 days of age. He found that the most accurate way to differentiate between genders was to measure the length of the eagles' foot pads and the depths of their beaks.