Get to know A Bald Eagle Nest.

a bald eagle nest
A Bald Eagle nest on a dead slash pine in Florida. Photo: Florida Fish and Wildlife Conservation Commission.

A Bald Eagle nest can be spotted from a distance due to its large size.

From our own collective experience, people who live near a Bald Eagle nest are interested in learning about the nest’s facts and activities; since the adults return every year until the time the eaglets fledge from the nest.

The bald eagle is perhaps the most recognizable and emblematic bird in North America. In the year 1782, this majestic Bald Eagle was declared America’s National Bird. 

This article goes over some of the most interesting aspects and facts about Bald Eagle’s nests.

Table Of Contents

Scientific Name: Haliaeetus leucocephalus.

Meaning of the Name:

  • Haliaeetus: Latin: A sea eagle.
  • leucocephalus: Greek. leuko= White and kephalus=white head.

A large Eagle nest is known as an Aerie.

basic measures of  bald eagle nest
The diameter and depth (of height) are the most common metrics used to describe the size of a Bald Eagle Nest. The “Bole” is the central circle where the eggs are laid. The Bole is lined with grass, moss, and other soft nesting material.

Bald Eagle Nest Measurements

When it comes to nest size, the Bald Eagle holds the world’s record as the largest tree nest ever recorded, not only for a bird but also for any animal.

This is because bald eagles construct nests that are reused every year. The eagle pair adds nesting material on top of the existing nest at the beginning of every breeding season, increasing the nest’s size and height or depth.

The majority of Bald Eagle nests are roundish, but some are elongated and even shaped like a triangle. The shape of a nest is somewhat determined by the configuration of the tree branches that support it.

Bald Eagles can use the same nest for over three decades. The following table shows the largest, oldest, and heaviest Bald Eagle nests known in North America.

Nest DiameterNest Depth
Typical Bald Eagle Nests1.5 – 1.8 m (4.9-5.9 ft)0.7-1.2 m (2.3-4 ft)
Oldest Eagle Nest Ever.

Locality: Vermillion,
Ohio.
 Used by Bald Eagles for 34 years.

2.7 m (8.8 ft)
3.6 m (12 ft)

Estimated Weight:
2 metric tons.
Largest Nest on Record.
Locality: St. Petersburg, Florida.
2.9 m (9.5 ft)6.1 m (20 ft)
bald eagle nest with the right branch configuration
Typical Bald Eagle nest that has been used for several years. The branches’ configuration that supports the nest is ideal for this nest to continue growing in height, maintaining the nest stable. Some nests do not have the ideal configuration of branches for vertical growth and become unstable as the nest gains height over years of use. Photo: U.S. Fish & Wildlife Service.

Nest Composition

The nest is composed of thin branches interwoven in an unorganized manner. The nesting material used is about as thick as a thumb on average. Some pieces of nesting material (branches) are thicker and others thinner.

The base of the nest is generally composed of larger and thicker branches. The top part is composed of shorter and thinner branches.

The central round area, where the eggs are laid, is known as the “bole” of an eagle’s nest and measures about 33 to 44 centimeters (13 to 17.3 “) in diameter and about 10 centimeters (4” ) deep.

For the final touches before the nest is ready for the female to lay the eggs, both the male and female bring dry grasses, moss, and dry algae and other soft material to line the nest’s center. The adult eagles also use their own down feathers to line the bole area.

When Do Bald Eagles Build Their Nests? 

The time bald eagles start building a nest varies with latitude or from the south to the north. 

Generally speaking,  eagles in the warm south start nesting earlier than eagles in the northern states, Alaska, and Canada. 

Bald eagles can start pre-breeding activities as early as 1 to 3 months before initiating nest construction and egg-laying.

Telltale signs or pre-breeding activities include:

  • Observing the eagle pair perched on branches near an existing nest. 
  • Pairs that do not have a nest begin scouting the area for potential sites to build a new nest. It is not common to see pairs that start a nest and abandon the attempt to restart another nest, perhaps on a better tree.

Approximate dates of the initiation of Nest Building and Maintenance activities from the Southern region to the North

Region, State or ProvinceInitiation of Breeding Activities
FloridaNest building and maintenance begins in late September through early October.
OhioNest building begins in February. Birds that did not migrate repaired their nest throughout the year.
Amchitka Island, AlaskaBirds begin as early as January 20th. Field observations indicate that while the resident pair was observed repairing their nest year-round, they started to spend time perched close to the nest in December.
Southeast AlaskaBirds begin to build nests in April.
Saskatchewan, CanadaBald Eagles here build or repair their nests in September before migration. Upon returning from the wintering grounds in April, the birds continue building or repairing their nests. 
adult bald eagle bring nesting material
A Bald Eagle taking nesting material. To judge by the type of nesting material this bird is taking, its nest is nearly finished, and the birds now are working on the bole. Hence this bird is now collecting moss. Photo: Marneejill/Flickr/CC by 2.0

Why The Differences Between Regions? 

The difference in timing between the North and South appears to be linked to egg hatching. 

Eagles start early so that by the time eggs hatch, in approximately 35 days after laying, temperatures are warmer and food is plentiful for the parents to feed the hungry baby eagles in the nest.

When Do Bald Eagles Complete their Nests?

The following is the approximate time of the year when bald eagles complete or finish building or repairing their nests. 

Bald Eagles start laying eggs when their nest is finished. Hence, the beginning of egg-laying provides an approximation of the dates the eagles finished building their nest.

As with other parts of the nest-building process, the time of completion of the nest varies throughout North America.

RegionApproximate date of Egg Laying/End of Nest Building.
FloridaEgg-laying may start as early as October and as late as April.
Most incubations are initiated in December through January.
Chesapeake Bay, MarylandEgg-laying starts the first week of January. By the end of January through the end of February, birds are incubating eggs.
Province of Saskatchewan, CanadaIt appears most of the egg-laying occurs in the second half of April.  
Yellowstone ecosystem, WyomingEagles laid eggs from early March through mid-April. Birds that nested at higher elevations started to lay eggs later than March.  
Arizona Eagles start to lay eggs in January through late mid-February.
Country of MexicoEagles appear to initiate egg-laying from late December through early January.
Alaska and Yukon TerritoryThe egg-laying period extends from late April through the end of May, peaking in the second week of May.

Division of Labor During the Nest Building. 

Once the eagle pair chooses a place to nest, both the male and female begin to gather nesting material and bring it to the nest.

It is unclear which sex contributes more or less towards the construction of the nest. However, once the nest’s base is in place, the female tends to stay on the nest and arranges the nesting material the male brings.

The eagles obtain the nesting material from the surrounding trees or the ground. Though, field observations indicate that eagles can travel over a mile to get nesting material. 

When they get branches from adjacent trees, an eagle flies by a tree and break off outer branches using its talons. 

Eagles will also descend to the ground to pick branches of the right thickness and size.

How Long Does a Pair of Eagles Take to Build a Nest? 

The time it takes for a pair of eagles to build a nest is highly variable. Some pairs have been recorded to take up to 3 months since they started to bring the first piece of nesting material to the nest site.

Some pairs build a nest in half that time, while others, particularly those that return to an existing nest, can build a nest in 5 days by adding material on top of the existing nest. 

Birds that return to the same nest only need to add new branches on top of the nest. They spend time bringing fresh lining material to the “bole” or center of the nest to prepare the nest for laying the eggs.

Like in other eagle nests, the adult eagles continue bringing additional nesting material when the female is incubating the eggs and even when the chicks are on the nest.

Oftentimes Eagles bring branches with leaves on them. It has been suggested that this practice has the purpose of acting as an insect repellent.

eagle arriving at the nest
A key feature that a nest tree must meet is having unobstructed access to the nest or an adjacent branch where the eagles can land and take off. Photo: U. S. National Park Service/Flickr/CC by 2.0

Where do Bald Eagles Build Their Nests?

When it comes to choosing a place to build a nest, bald eagles are rather flexible.

Bald Eagles adapt to the prevailing nesting opportunities in the regions they occur. They can build a nest on trees of various heights, on short vegetation, on ridges, cliffs, and even on bare ground where trees are not available.

All eagles need to start a nesting attempt is a substrate to keep the nest off the ground to avoid ground predators. Eagles that nest on the bare ground only do so on small islands with no ground predators.

 

Nests on Trees.

In regions where trees are available, bald eagles nest exclusively on trees. 

The type and characteristics of the tree that eagles select to build a nest are highly variable. However, there are some commonalities. 

The Bald Eagle is a large bird with long wings and heavy bodies. Hence, its flight describes a flat trajectory, so to speak. The Bald Eagle does not have the flight maneuverability of a small bird.

Hence, the nest tree needs to have one or two large branches that offer easy and unobstructed access to land on a branch and to take off from it.

Related: How to Age and Identify a Juvenile and Sub-Adult Bald Eagle.

Characteristics of Nest Trees Chosen by Eagles.

In forested areas, the bald eagle chooses the tallest and emergent trees.

Common characteristics of trees chosen by eagle to nest include:

  • Height: Studies indicate that trees where eagles nest in forested areas vary in height from 20 to 60 m (65.6-197 ft) for an average of 28 m (92 ft). The main condition is that the nest tree is taller than the rest and that the surroundings are free from obstacles.
  • The thickness of tree trunk:  Ornithologists have determined that bald eagles use nests of 50 to 190 cm (20 to 75″ ) in diameter for an average of trees of 82 cm. While the diameter of the tree is important, equally important are the branches the hold the nest.
  • Branches that support the nest: A tree suitable to support a nest must have the right formation of forked branches, mostly stemming from the main trunk, that can hold the very first pieces of nesting material to initiate the nest and the volume and weight of the nest subsequently.

Eagles, particularly in hot and sunny regions, tend to place their nest under the shade of the canopy. But this is variable as some pair nest in trees without any canopy above the nest.

Nests in Semi Open Habitats.

In semi-open habitats with scattered trees surrounded by short scrub or grasses, flying eagles’ access to trees is not of much concern. Therefore, trees do not need to be very tall to be suitable for nesting eagles.

In South Florida, the Bald Eagle generally nest in tall pine trees, but some pairs build nests at no more than 20 m from the ground.

bald eagles nesting on saguaro cactus
While Bald Eagles are rather flexible with their nesting sites, a Saguaro Cactus in Arizona is certainly a rare event. Photo: Courtesy of TV20NEWS.

Bald Eagles Nest on Mangroves and Cactus.

There is plenty of food for the Bald Eagle in the mangrove dominated coastal areas in South Florida. Because eagles like to nest near water and their food, the Bald Eagle builds nests on Mangroves.

The average height of mangroves in South Florid is approximately 6 m.

Although rare, Bald Eagles in Arizona nest in Saguaro Cactus.

bald eagle incubating eggs on a beach nest.
Eagles nests on the bare ground are rather rare. This nesting eagle pair chose to nest on a sandy beach on Smith Island, Maryland. Photo: Bryan Watts, Center for Conservation Biology. – Beach Nesting Eagles.

Nests  in Treeless Areas.

There are many areas in the bald eagle’s range where food is plentiful, but trees are nonexisting. 

In treeless conditions, bald eagles nest on low ridges, cliff ledgers, sea stacks. Eagles have also nested on bare beaches on islands without predators that can harm the eggs and baby bald eagles.

Alternate Nests.

Bald Eagles tend to build multiple nests within their territories. This particular behavior has been observed in forested and semi-open habitats where the eagles can pick several trees to build nests on.

Some pairs have been observed building up to 5 nests within a territory.

The territorial pair generally has a preferred nest that it uses every year. The alternate nests are generally used when the nesting attempt fails on the main nest. The birds may try again on one of the alternate nests.

In contrast to switching to alternate nests, some pairs will continue nesting in the same tree even after the tree dies, and there are only some of the thickest limbs left holding the nest in place. 

Immature birds may build practice nests, which are rarely used for breeding purposes.

Interestingly, in regions where trees are scarce or entirely missing, the eagles tend to have only one and seldom two nests.

Video: All About Eagle Nests

REFERENCES:

  • Buehler, D. A. (2020). Bald Eagle (Haliaeetus leucocephalus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.baleag.01
  • Gill, Frank (1995). Ornithology. New York: W.H. Freeman.
  • Grubb, T. G. (1983). Bald Eagle activity at an artificial nest structure in Arizona. Journal of Raptor Research 17:114-121.
  • Herrick, F. H. (1932). Daily life of the American eagle: early phase. Auk 49:307-323.
  • Howell, S. N. G., and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford, United Kingdom.
  • Sherrod, S. K., C. M. White and F. S. L. Williamson. (1976). Biology of the Bald Eagle on Amchitka Island, Alaska. Living Bird 15:145-182.
  • Swenson, J. E., K. L. Alt and R. L. Eng. (1986). Ecology of Bald Eagles in the greater Yellowstone ecosystem. Wildlife Monographs 95.
  • The Sibley Guide to Birds. David Allen Sibley, Published by Alfred A. Knopf, 2000.

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