Joy is a juvenile Bald Eagle (Haliaeetus leucocephalus) who arrived here on Feb. 20, 2016 from the Alaska Raptor Center in Sitka. Until she reaches the age of five, she will not have the characteristic white head and tail feathers of an adult. The name “Bald” Eagle originates from the old English spelling of “balde” which means “white.” Bald Eagles can weigh up to 14 lbs. and have a wingspan up to 8 feet. They prefer to live near water and typically nest in tall trees. Arizona is home to a desert nesting population of Bald Eagles that does not migrate north for the breeding season. Classified as sea eagles, they consume primarily fish, but will eat waterfowl, gulls, small mammals and carrion. In fact, Bald Eagles are known as kleptoparasites, commonly stealing food from others such as Osprey (Pandion haliaetus). The Bald Eagle has been our national symbol since 1782. Today it faces many threats, most notably loss of habitat and wind farms.
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 lbs. and is rather timid when compared to Joy, the female with whom he shares his enclosure. 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.