Leopold (“Leo”) is a 12-year-old partially flighted Bald Eagle (Haliaeetus leucocephalus) who was transferred to us from the World Bird Sanctuary in Missouri. He is named for Professor Aldo Leopold, the father of wildlife management. Leo weighs approximately 10 pounds and is more timid and smaller than a female bald eagle would be. Behaviors differ amongst males and females, as do physical features. In general, females are larger than males by as much as 1/3. They have larger beaks, feet, wings, etc. and attitude! In fact, an eagle researcher named Gary Bortolotti found that two body measurements could be used to accurately sex eagles: beak depth and length of the hallux (hind talon). However, this can be complicated by where the eagle originated. Bergmann’s rule is an ecogeographical rule that basically states that birds living in colder climates (north) are larger than birds living in warm climates (south). This is beneficial when heat retention or loss is necessary. These differences in male and female Bald Eagles are referred to as “reversed” sexual dimorphism because the female is the larger of the two. Typically in nature, males are larger and may look different than females, which is called sexual dimorphism.