Bald Eagles face many threats, including habitat loss, lead poisoning, electrification, and illegal shooting. After WWII, Bald Eagle reproduction rates plummeted as DDT interfered with their ability to produce strong eggshells as the weight of the birds often crushed the eggs during incubation. By 1963, only 487 nesting pairs of Bald Eagles remained in the United States. The banning of DDT and the protection offered by listing under the Endangered Species Act have helped the Bald Eagle population to recover to upwards of 10,000 nesting pairs. Teton Raptor Center is using DNA collected from a 34-year-old Bald Eagle that we treated in our rehabilitation program, as well as other samples from known breeding eagles from the 1980s and 1990s, to study how the population has expanded within and beyond the Greater Yellowstone Ecosystem. Since 2016, we have been banding and taking DNA samples from Bald Eagle nestlings to map their genetic relationships and better understand population genetics of a recovered species. This project is in collaboration with Wyoming Game and Fish and Oklahoma State University.
We have both an experienced rock climber and trained arborist on our team. In mid-May, they climb large cottonwoods and the occasional pine tree to get into an eagle's nest and band the nestlings
Bald Eagle parents generally leave the nest when our climbers approach the tree and land in a nearby tree. Once our climbers leave the area, the parents will come back, check over their chicks, and resume their parenting duties. We complete our work in minimal time, and we have never had parents abandon chicks after our work.
We aim for nestlings between 4-6 weeks of age. At 4 weeks, bald eaglets are full-grown, so bands can be placed on their legs without worry of it slipping off. At this age eaglets also can thermoregulate on their own, so there's no health risks when the parent leaves the nest. Eaglets begin leaving the nest and learning to fly at 8 weeks of age, so ideally we're in the nest before they leave.
Banded birds all receive a federally regulated metal band with a unique 9 digit number to identify individuals. All banded eagles, regardless of age, receive these bands, and the Bird Banding Lab assures all eagles across the country have a unique code. These bands can only be read when a bird is in hand. In addition to these bands, Teton Raptor Center places a metal color band on eaglets as well. These bands have a 2 digit number/letter combo, unique to all birds we personally have banded. These bands can be read from afar using binoculars or a scope, allowing us to collect data on birds without having to recapture them.
Since we band at such a young age, these birds are essentially hatched with these bands, and wear them their entire lives. Birds that have been recaptured show little to no wear on the bird's legs from the bands.
For each eaglet banded, we take a variety of measurements, such as head length, talon length, and weight. All this data is submitted to a larger pool of bald eagle measurement collection, contributed from researchers all over the country. We also draw a small blood sample in order to genetically map each eaglet.
Parents put an extraordinary amount of time and energy into laying eggs, incubating them, and raising their nestlings, that it would take a much larger event to convince them to abandon their young. That being said, we still move quickly and efficiently with our work, minimizing our time in each nest to not push parents away. It would be contradictory to our work if parents abandon their young, and we take every precaution to prevent this.