Do juvenile bald eagles prey on other eagle nests?

Posted on September 14, 2016. Filed under: Animals, Biology, Birds, Questions | Tags: , , , , , , , |

Question answered by Doug Halford, Wildlife Biologist, WAI ESER Program   

eaglesWell, it is unlikely but not impossible.

The 35 days of incubation duties are shared by both male and female, but it is the female who spends most of her time on the nest. Trading places on the nest can be a tense time. The brooding parent may have to call for relief, or may be reluctant to leave and have to be pushed off the eggs or young.

During incubation, 98 percent of the time one parent remains on the nest; not only to keep the eggs warm but to protect them from squirrels, ravens, and gulls which will break open and eat the eggs. If the adults leave the nest unattended too long, it can be consequential for the eggs.

Territory
Bald eagles are highly social outside of the nesting season, but are extremely territorial when nesting. Like many other animals, eagles establish and defend a territory around their nests.

This territory is typically about one mile in diameter and is the space that each pair claims as their personal resource. Eagles will actively defend their territories from any perceived threat. While defense of the nest from direct predation is important, territory defense is more about food than it is about safety. Having a reliable and readily available food source is crucial to the success of a nest. Therefore, an eagle pair will chase off other eagles, osprey, red-tailed hawks and other competitors.

Soaring

Eagles soar to great heights above the earth’s surface to hunt and travel. This skill is a combination of two things: the differences in how quickly different parts of the earth’s surface heat up and the broad wings of the eagle.

eagles2During the day, as the sun shines down on the surface of the earth, some places warm up faster than others. Some places, like parking lots and water, absorb more of the sun’s heat than others, like grassy fields.

Different temperatures on the earth’s surface cause the air above these surfaces to also have different temperatures. When the warm air is next to the cooler air, the warmer air rises above the cooler air. This rising part of the air is called a thermal. A bald eagle’s wings are specially adapted to take advantage of these rising thermals of air.

When an eagle first leaves its perch, it uses its broad wings and powerful flying muscles to get higher. Once an eagle is up in the air, its wide wings allow it to stay up with less work. When an eagle comes across a thermal, it can use this rising hot air to really climb. By circling over the middle of a rising thermal, a bald eagle can just spread its wings, allowing the warm air to lift the eagle to heights up to 3 miles above the surface of the earth.

To see how thermals work, make a solar chimney.

eages3Materials: 3 tin cans (large soup cans), can opener, masking tape, thumb tacks, white paper or aluminium foil, scissors, large paper clip, blocks or books

  1. Use the can opener to remove both ends from the three large cans. Be careful of sharp edges. Tape the cans together to form a column.
  2. Make a pinwheel. Cut a 6-inch sheet of paper or aluminium foil diagonally from each corner to within 1/2 inch of the center. Bend every other point back to the center of the square. Tape the points together at the center.
  3. Bend a piece of wire into an elbow shape and tape it, elbow up, on both sides of the top of the can column. Tape a thumb tack to the piece of wire at the elbow.
  4. Find a spot indoors that receives direct sunlight. Position the tin can column on top of two blocks or books.
  5. Leave room between the books for space between the ground and the bottom of the can column.
  6. Balance the pinwheel on the tack in the middle of the tin can column. What happens?

As the heat of the sun warms the air inside the column, the pinwheel will start to spin.


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