Hanover Bald Eagle Blog # 3 - 2023
Jan. 25, 2023
In partnership with Pennsylvania Game Commission and Comcast Business .
Each day the Hanover nest looks more and more comfortable due to all the soft materials (including straw) that the pair has brought home. If their eggs are to hatch successfully, they must be nestled within a protected cup large enough for two eggs. The pair will line this cup, also called a bole, with soft materials such as their own downy feathers. The base layer of the nest is composed of interwoven sticks, which provide the necessary stability for a family of very large birds (together the two adults weigh at least twenty pounds).
The Hanover parents first constructed their nest nearly eight years ago, in 2015. They have returned every year since, a pattern known as site fidelity, and as long as their nest meets the following criteria, they will likely continue making home improvements to the same cluster of sticks, every year, with dedication.
An eagle nest needs to offer the following:
- Protection from nest predators (mostly mammals and great horned owls).
- A commanding view of the area for hunting and guarding purposes.
- A strong tree.
- Easy flight access in and out of the nest.
- Proximity to water.
- Shelter from the elements.
Understandably, with all of these considerations, new parents can get it wrong. Therefore, young eagles (2-4 years old) sometimes create practice nests before they are ready to breed.
Bald eagles typically choose to nest in living trees with broken tops, and begin construction or refurbishing 1-3 months prior to laying. Bald eagles are diligent architects, rearranging sticks several times over to ensure they land in the right spot. Eagle nests are often referred to aeries, a Medieval Latin and Old French word meaning “nest” or “lair,” and referring to particularly high dwellings on cliffs or mountains.
Interestingly, not all bald eagles build nests in trees. In Pennsylvania this is the norm, however in treeless regions like parts of Alaska and islands off the California coast, bald eagles may nest on the ground.
Nesting materials vary by region — in the Pacific Northwest nests may contain kelp and driftwood while here at the Hanover nest we see the parents fly in with straw and corn husks. In Florida observers watched an eagle pair cushion their nest with fourteen inches of Spanish moss over the course of one month! Sometimes, strange items have found their way into eagle nests, including clothes pins, plastic bottles, light bulbs, stones, duck decoys, a rubber rat, golf balls, and even items of human clothing. These anomalies are thought to be a way for eagles to signal to others that the nest is occupied, but no one knows for sure.
Nest sizes vary based on how long they’ve been used, but a typical bald eagle nest clocks out at 5 feet across and 3 feet deep. The largest bald eagle nest ever recorded was built in St. Petersburg, Florida. This whopper, which is listed as the largest known bird nest in the Guinness World Records, came in at 9.5 feet across, 20 feet deep, and weighed nearly 3 tons — the same as a baby blue whale!
Here are 3 time-lapse videos of eagle pairs building and sprucing up their nests. You can see how the pairs consistently add soft material to the middle of the nest. Enjoy!
Sources
Explore Birds Bats Bees. (2017, October 26). Eagles build a nest over 3 months at Greenwood Cemetery in Orlando [Video]. YouTube. https://www.youtube.com/watch?v=2a293PHKg1M
Explore Birds Bats Bees. (2017, October 26). Bald Eagles Build Nest - Decorah Eagles Time-lapse [Video]. YouTube. https://www.youtube.com/watch?v=46ZQmiy2oNc
Gerrard, Jon M. & Bortolotti, R. Gary. (1988). The Bald Eagle: Haunts and Habits of a Wilderness Monarch. Smithsonian Institution.
Go Data. (2021, April 26). Animals Eggs Size Comparison [Video]. YouTube. https://www.youtube.com/watch?v=E8Ns4JRkRNI
Guinness World Records Limited. (2022). Largest bird’s nest. https://www.guinnessworldrecords.com/world-records/largest-birds-nest
HDOnTap. (2018, January 31). 2018 Hanover Eagles - Nest Rebuilding Time-Lapse [Video]. YouTube. https://www.youtube.com/watch?v=BCZstLKiuxA
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