The proud Bald eagle is one of the world's most well-known and handsome birds. Bald eagles are found in every US state except Hawaii and much of Canada and northern Mexico. These adaptable birds have been studied closely for centuries, and their nests are of particular interest given their colossal size and weight.
So why are Bald eagle nests so large, and what are some other interesting facts about Bald eagle nests?
Bald eagle nests are constructed with care and attention over the course of 1 to 3 months. Nest building is very much a cooperative process, though the female often takes the lead in building the nest while the male supplies material.
The stand-out feature of a Bald eagle nest is size - the average nest measures around 1.2 to 1.5m in diameter (4 to 5ft) 60 to 120cm deep (2 to 4ft). Bald eagles add around 1 to 3ft of new material to the nest every year. The largest Bald eagle nest, found in St. Petersburg, Florida, was 2.89m in diameter (9.5ft), 6m (20ft) deep, and weighed almost 3 tons!
Despite their majesty, Bald eagles are pretty lazy and spend a lot of time in their nest. Benjamin Franklin said himself that the Bald eagle was a lazy bird that didn't deserve to be the USA's national emblem. Of course, with nests that large, you can't really blame the Bald eagle for being somewhat of a homebody!
Read on to learn more about this majestic raptor's nesting habits and behaviours!
The nest of a Bald eagle with one chick inside
Bald eagles nest right across the USA, Canada and northern Mexico. They usually choose tall, mature trees that are solid and stable with strong, broad forks on which to build their nest.
Despite preferring tall trees, Bald eagles build ground nests where trees are not available, especially in Alaska, Canada, islands off the coast of California and Arizona. Ground nests are usually built on cliffsides or next to rivers.
Bald eagles are thought to evaluate the food supply of the local area prior to choosing their territory. Since Bald eagles are adept at fishing, they prefer to stay close to rivers, lakes or waterways. Coastal populations will happily fish from the area too.
A large bald eagle nest
Bald eagles generally tend to nest in conifers, firs, oaks, hickories, cottonwoods and aspens.
One study found that chosen nest trees typically measured around 20 to 60 m in height and 50 to 190 cm in diameter. While living trees with strong canopies are preferred, Bald eagles do also nest in dead trees, particularly in more arid or treeless regions.
Bald eagle nests are large, broad and deep. The shape is often described as a wine glass without the stem - it extends upwards with a deep, walled cup. Nests built on the ground are flatter but are still built up from the floor to create an enclosed space.
The primary structure of the nest is created from dense, large sticks; some can measure around 1m in length. Smaller sticks, twigs and foliage are laid inside the main structure, which is lined with mosses. Bald eagles are creative with what materials they use to build the nest - some coastal nests even feature driftwood or kelp.
A pair of breeding Bald eagles in their nest
A typical Bald eagle nest measures around 1.2 to 1.5m in diameter (4 to 5ft) 60 to 120cm deep (2 to 4ft).
A Bald eagle nest currently holds the Guinness World Record for the biggest nest ever recorded. Found in St. Petersburg, Florida, the nest measured 2.89m in diameter (9.5 feet) and 6m (20 feet) deep! It was examined in 1963 and was estimated to weigh almost 3 tons.
Bald eagles prefer to nest in tall, strong, mature trees. One study found that chosen trees measure around 20 to 60 m in height (65 to 200ft) and 50 to 190 cm in diameter (1.6 to 6ft).
The nest itself is typically built at the height of around 15 to 25m. Some nests are built as low as 5m above the ground.
In treeless or coastal regions, Bald eagles do choose to nest on the ground. This is common in Alaska, Canada, California, Minnesota, Florida and Arizona. When nesting on the ground, Bald eagles often choose a cliffside spot.
Bald eagles nesting above the ocean in Canada, British Columbia
Bald eagle nesting occurs at different times, depending on the latitude. In the southern areas of their range, e.g. the states of Florida, Texas, Arizona, and northern Mexico, Bald eagles start building nests as early as late summer or as late as mid-spring. In the north USA and Canada, nest building typically starts in early spring.
The warmer it is in the region, the more flexible Bald eagles are with their breeding season. The breeding season in the south is much longer compared to the north. Virtually all Bald eagle nests are finished by late winter in around February.
Bald eagles are either sedentary or migratory. Some Bald eagles migrate in winter or at other times of year to pursue food. But for much of the year, Bald eagles spend their time in and around their nests.
Bald Eagle with eaglet in the nest
The main structure is interweaved from larger sticks. Then, the pair will begin to fine-tune the nest for warmth and comfort by weaving smaller twigs and greenery into the primary structure.
Both the male and female cooperate to build the nest. The female is often responsible for building the initial structure while the male forages sticks from nearby.
In some areas, the eagles go out of their way to line the nest with soft mosses. In addition, feathers and down shed by the eagles are used to insulate the interior of the nest.
Sticks can be carried from as far as 1km from the nest. One pair of Bald eagles carried sticks from as far as 1.6km away!
A bald eagle deliveries nesting material to the nest with its mate looking on
The average bald eagle nest takes between 1 and 3 months to build. Tree nests take longer to build than ground nests.
Bald eagles typically show high breeding ground fidelity, which essentially means that they prefer to return to the same place to breed and nest every year. Once a successful nest is established, pairs of Bald eagles will replenish and maintain it intently all year round.
Each year, nests may increase in size by some 1 to 3ft, which explains why Bald eagle nests tend to grow and grow.
One nest in Ohio was reportedly used for 34-years before the tree blew down, which presumably suggests that a new pair ‘moved in’ once the former owners died (as Bald eagles do not tend to live for more than 30 years).
Some pairs of Bald eagles have been observed building an alternate nest, though this is relatively rare and amounts to around 1/10 pairs in the very few regions where this is observed, such as Saskatchewan in Canada.
A bald eagle adds a branch as its final touch to completing the nest, Yellowstone National Park, Wyoming
The average bald eagle egg measures around 7.0 to 7.6 cm in length and 5.3 to 5.6 cm in breadth and weigh between 100 and 130g. They are dull white and rarely have brown spots.
Bald eagle eggs are large and sub-elliptical, which means they’re more rounded than a typical bird egg. The widest point is of similar width to a tennis ball.
The month that bald eagles lay eggs varies depending on their location. For example, in Alaska and Yukon Territory, eggs are generally laid from late April until May. In parts of Mexico, eggs are usually laid between December and early January. Generally speaking, the higher the elevation, the later the egg laying takes place.
Egg laying by place and time of year:
The Bald eagle breeding season is much extended in the south where it’s warmer throughout the year.
Three juvenile bald eagles in the nest, waiting to be fed
Generally speaking, Bald eagles will only produce one clutch per season. However, if the eggs are destroyed or taken by predators, then sometimes another clutch will be produced.
Bald eagle chicks typically fledge after around 10 to 14 weeks but can stay in and around the nest for the following 2 to 3 months.
Parental feeding continues during this time, and the juvenile eagle will not leave to establish its own territories until up to 6 to 8 months or so after hatching. Like most eagles, Bald eagles have a long lifecycle and chicks are not hasty to leave their parents.
A pair of bald eagle chicks in the nest
The average Bald eagle nest weighs around 1 ton. However, the heaviest nests weigh over 2 tons, and the heaviest recorded is thought to have weighed almost 3 tons! It holds the Guinness World Record for the biggest bird’s nest.
Where trees are lacking, Bald eagles can nest on the ground. This is more common in arid environments where trees are limited, e.g. parts of Alaska, Canada and Arizona. When they live in coastal regions, Bald eagles often nest on cliffsides.
Bald eagles nest in a variety of coniferous and deciduous trees, including conifers and pines. The main criteria are that the tree must be relatively tall and strong with a wide fork.
In Florida, Bald eagle nests are found in shorter, younger trees than in most other regions. While Bald eagles tend to opt for large, mature trees that are more than 0.5 to 1m in diameter, studies revealed that Florida nests are built in younger trees that measure just 30cm in diameter.
Bald Eagles may continue to incubate unhatched eggs for days, if not weeks longer than the standard hatching time. This is generally in the case of when the eggs haven't started to break up or when there is no nestling already in the nest.
If there is a hatchling in the nest, they're much less likely to continue incubating, due to the fact that it'll just get in the way, and there simply wouldn't be enough room for the adult to continue incubation.
Eventually, bald eagles will give up and unhatched eggs generally will either be trampled or, in rare circumstances, adults will feed it to the eaglets in the nest. After this, the shell will be usually discarded from the nest.
Research and data shows that anywhere between 10% and 25% of bald eagle eggs are either lost or never hatched.
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