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Bald Eagle

(Haliaeetus leucocephalus)

Introduction

 

We all stop to watch a Bald Eagle soaring on the rising air currents and admire its effortless flight.

 

The Bald Eagle's scientific name  Haliaeetus leucocephalus, is a mouthful but it combines hali (meaning sea),  aeetos, ( eagle), leukos (white) and cephalos (head). The word “bald” is thought to come from the old English word “balde,” meaning white. There is also possibly a connection to the word “piebald” since “bald” in this word does not mean hairless but refers to a white patch.

 

The chemical DDT is part of the Bald Eagle’s story. DDT was used as an insecticide in agriculture. After it was sprayed on crops, it washed from the soil into the lakes and  contaminated the fish the Bald Eagles were eating. The consequence of this was fragile shells on the eggs that often broke in the nest and the significant decline in the Bald Eagle population.  Most uses of DDT were banned in Canada in the mid 1970’s, all uses were discontinued in 1985 and all existing stocks were to be disposed of by 1990. After almost going extinct, the slow increase in the population of these raptors is a true success story.

 

This webpage focuses on increasing our knowledge and admiration of this bird. 

The two headed eagle is one of the shishalh nation’s most sacred symbols. This large, colourful piece was created by the late indigenous carver Tony Paul and is located at the Tsain Ko shopping mall in Sechelt. It depicts the double-headed k’aykw (eagle) on top of the Tsain-Ko (double headed serpent).

Range

The Bald Eagle is the only eagle exclusive to North America. In Canada, healthy eagle populations are found in the boreal forests of Alberta, Saskatchewan, Manitoba and northwestern Ontario. Small groups of Bald Eagles also make their homes in southern Quebec, Cape Breton and along the coast of Newfoundland. But, by far the largest concentrations of this bird are found along the Pacific coast of British Columbia. The Coast, with its forested areas near large bodies of water provides the ideal combination of large, tall trees and extensive fishing grounds.

Note: Golden Eagles may also be seen on the Sunshine Coast but because they prefer open country, drier inland conditions and prey on small mammals, they are rarely seen here.

Characteristics

Soaring over Hotel Lake, the brown body, white head and tail and hooked yellow beak of the Bald Eagle make this predatory raptor easy to recognize. Males and females have identical coloration. The only distinction between male and female is that females are about 25% larger than males. While female Bald Eagles weigh 10 to 15 pounds, males weigh 6 to 9 pounds. Bald Eagles are between 28 and 38 inches in height and have an impressive wingspan that measures from 5.5 to 8 feet. 

The Bald Eagle does not attain its distinctive brown and white colouring until approximately 5 years old. Juvenile Bald Eagles look very different from adults—they are almost entirely brown, with occasional white markings on the undersides of their wings and chest. As the juvenile gets older, the bill turns from dark brownish-black to yellow, and the head and tail turn white. 

Feet:     At a point on their leg that is actually their knee, their feathers stop and thick yellow scales begin.  Four muscular toes (three facing forward and one facing backward)  end in razor-sharp, black talons. On the bottom of their feet tiny projections called spicules help them grasp their prey. These feet have evolved into a powerful tool for grabbing, crushing, stabbing and tearing; a tool perfectly adapted to the Bald Eagle’s hunting strategy and handling of prey as you can see in the following video.

Wings:    The width between wing tips (wingspan) is about 2 meters for males and 2.5 meters for females. These wings are classified as passive soaring wings with long primary feathers that  spread so that the slots catch rising air currents. Although the Bald Eagle spends much time gliding, it can also vigorously flap its wings when needed, such as  when it swoops in to catch a fish. Beautiful and efficient, these wings allow the Bald Eagles to achieve 32-64 kph (20-40miles per hour ) in normal flight,  to dive at speeds of 120-160 kph (75-100 mph) and to reach heights of 10000 ft.

 

A Bald eagle has approximately 7,000 feathers. When it loses a feather on one wing, it will also lose a matching feather on the other wing to keep balance. These amazing wings also allow the Bald Eagle to reach shore without swimming or flying as it will sit on the water and uses it wings to “row”. 

Although there are many opinions and stories about Bald Eagles flying off with prey and pets, best estimates place the bald eagle’s lifting capacity at 3-5 pounds. There are a number of aerodynamic factors; an important one being momentum and speed. Biologist Ron Clarke has been quoted as saying, “On a wide-open beach, I have no doubt that an eagle with a full head of steam could pick up a six- or eight-pound dog and just keep on going. If it landed to kill a ten-pounder, and then tried to pick up and fly from a dead stop, could it get off the ground? Probably not.”  (Alaska Fish and Wildlife News, Jan. 2008)

Eyes:     Bald Eagles have huge eyes that fill most of their skulls. Although a full grown adult weighs only about 14 pounds, its eyes are the same size and weight as human eyes.

 

Predatory birds typically have excellent eyesight, but even within this group the Bald Eagle’s eyesight is remarkable. An eagle's vision is exceptionally sharp because each eye has two foveae (areas of acute vision) as compared with the human eye which only has one. The cones in the eagle's fovea are very small and tightly grouped, allowing the eagle to see small details from extreme distances. You might compare an eagle’s eye to a modern computer screen, with densely studded pixels giving extraordinary clarity and sharpness to every image.

Bald Eagles have a 340 degree field of vision and can see clearly about eight times as far as humans can. They also have two focal points that allow them to see in front of them, and at a 45-degree angle on either side of them…at the same time. Their amazing distance vision allows them to spot and focus on prey such as a rabbit at a distance of about two miles. When fish are the prey, the fact that light is refracted as it passes from air to water makes it difficult to “see” exactly where the fish are. As Bald Eagles mature they become amazingly accurate “fishermen”; a result of their brains and eyes working together to overcome this refraction error.

In addition to its normal pair of eyelids, the eagle has an extra set of eyelids called nictitating membranes. These transparent eyelids move from side to side across the eye and close for needed protection without affecting the eagle's vision. 

Calls and Sounds:    Bald Eagles make several calls that are rather like sea gulls.  This is in contrast to many movies that depict eagles as screeching loudly.  The following short video will correct your understanding of Bald Eagle calls and re-tune your ears so you will recognize these sounds when you are out and about on Hotel Lake.

Life Cycle

Around 5 years old, when Bald Eagles display their mature brown, white and yellow colouring, they also become able to breed. They usually mate for life and after selecting a mate the pair will have one brood of 1 to 3 eggs per year. The young have less than a 50% chance of reaching adulthood.The life span in the wild is 20 to 30 years.

Courting:  Our understanding of how Bald Eagles choose their mates has largely come from our observation of the aerial displays that form a significant part of their courtship rituals. The most famous of these rituals looks very much like a game of “chicken” in which the pair gain altitude, lock talons and spin cartwheeling down toward the ground, breaking apart at the last minute.

Nesting:  Nest building can also be thought of as a courtship ritual that strengthens the bond between the pair. Bald Eagles tend to nest in tall, sturdy conifers that stick up above the forest canopy, providing easy flight access and good visibility. The female, who is thought most often to choose the nesting site, is looking for landscapes that provide water to drink, fish to eat, forest trees for shelter, a place to raise young, and perches for hunting and resting.

 

Working cooperatively, the male and female will take from 1 - 3 months to build their nest. They usually start building in the top quarter of the tree, below the crown, near the trunk, where branches are thick and strong enough to support the heavy nest. They interweave the sticks, and fill in spaces with grasses, mosses, lichen, and other fibers. Once it's built, a pair often uses it year after year, working on construction at the beginning of each nesting season to add materials, and line the  bole with down. Over time making these additions results in nests that average 5 to 6 ft. In diameter, 2 to 4 ft. in depth and close to 1 tonne in weight. Bald Eagles build the largest nests of any North American bird. The largest Bald eagle nest was found in St. Petersburg, Florida, in 1963, and measured a whopping 9 feet 6 inches wide and 20 feet deep. This giant nest weighed 4,400 pounds!

The female lays 1 to 3 eggs spaced over 3 to 6 days. She then settles in to incubate the eggs for a period of about 35 days. The eggs hatch in the same order and with the same spacing of time as when they were laid. Survival of the newly hatched chicks often depends on their place in this “pecking” order.  The first born is immediately fed,  grows stronger and competes for food more aggressively than the chicks that are born a few days later. Often the last chick born does not survive.

Development of Bald Eagle Young:

Week One: At hatching, the young are covered with a white or light grey down. Wet, exhausted, and unable to stand or stay warm,  they are totally dependent on the parents. The female parent does the majority of the brooding while the male parent provides most of the food for the family. From day one the hatchlings are fed raw meat that has been torn into bits (but not regurgitated) and fed bill to bill by the parent. Aggressive antagonistic behavior can appear shortly after hatching wherein the oldest, largest eaglet tries to dominate or even kill its sibling(s).

Week Two: The second down plumage, darker grey in color, begins to replace the first. As the week progresses  the eaglet becomes able to hold its head up and thermoregulate  (maintain its own body temperature under normal weather conditions without brooding from an adult).

Week Three: Black contour feathers on back, shoulder, breast and wings begin to emerge.

Week Four: Maximum body growth nears completion; flight feather development underway.

Week Five: Male and female parents bring relatively equal amounts of food. Parents begin spending more time away from the young and often perch in nearby trees.

Week Six: Young are able to tear pieces of food off and feed themselves, and begin to stand and walk.

 

Week Seven: Maximum body growth is nearing completion.

Weeks Eight – Twelve: Nestlings begin “branching.” They flap their wings while perched on the nest and hop onto nearby branches, practicing and building up flight muscles, coordination, and landing skills. After the first flight the eaglets may return to the nest a few times to spend the night (roosting) or to get food brought there by the adults.

After fledging, the young are still dependent on the adults to feed them for a period of up to a couple of months until they gain the experience and skills to find and catch their own food. 

Diet

Living in freshwater or coastal habitats and being carnivorous, the Bald Eagle eats mainly fish and birds. They especially love to hunt salmon, catfish and herrings, but will even eat crabs and other crustaceans. Small mammals such as rabbits and squirrels are usually a very small part of their diet. Like other raptors, the Bald Eagle will also steal prey and eat road kill.

Bald Eagles are described as opportunistic, shrewd, clever, and rather lazy predators. “Lazy” in the sense of “energy-conserving”; they will not enter a contest where the outcome is doubtful. Bald eagles rely on their speed and sharp eyesight to surprise their live targets. This is what makes waterfowl and fish in open water a prime target. Fish are a relatively risk-free target and provide the high saturated fat content that eagles need to thrive. 

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How is the Bald Eagle Doing in BC?

In BC the Conservation Data Center assigns a conservation status rank by placing each species and ecosystem on a Red, Blue or Yellow List to help set conservation priorities and provide a simplified view of the status of B.C.'s species and ecosystems.

Red List - Any species or ecosystem that is at risk of being lost (extirpated, endangered or threatened)

Blue List - Any species or ecosystem that is of special concern

Yellow List - Any species or ecosystem that is apparently secure or secure (least risk of being lost)

The Bald Eagle is currently on the Yellow List.

 

How We Can Help

For detailed guidelines for protecting the birds and their environment see Develop with Care 2014: Environmental Guidelines for Urban and Rural Land Development in British Columbia and Guidelines for Raptor Conservation during Urban and Rural Land Development in British Columbia (2013).

 

The following is quoted from the BC Government’s Develop with Care 2014 document Appendix G Fact Sheet 10 - Bald Eagles and Ospreys (PDF):

 

At Risk:   Although these and other large birds of prey are often seen soaring overhead, human activities can threaten their survival. The loss of available nesting and feeding habitats, as well as disturbance from human presence, reduces the birds’ ability to thrive and successfully raise their young.

Legally Protected:    It is an offence to possess, take, injure, molest, or destroy a bird or its eggs, or the nests of birds when occupied by a bird or egg (B.C. Wildlife Act, Section 34). Osprey and eagle nests are protected year-round, whether or not the nest is in use. Permission and a written permit from the Province are required to remove or modify a tree or snag containing an active nest of these species. Contact FrontCounter BC for information.

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This video from National Geographic Wild originates on a tributary of the Mississippi River and combines outstanding photography with opportunities to see amazing aspects of the Bald Eagle’s life. 

References

Develop With Care, Fact Sheet #10, (2014) Environmental Guidelines for Urban and Rural Land Development in British Columbia:   

https://www2.gov.bc.ca/assets/gov/environment/natural-resource-stewardship/best-management-practices/develop-with-care/fact-sheet-10-eagles-osprey.pdf

Guidelines for Raptor Conservation during Urban and Rural Land Development
in British Columbia (2013):

https://www2.gov.bc.ca/assets/gov/environment/natural-resource-stewardship/best-management-practices/raptor_conservation_guidelines_2013.pdf

National Wildlife Federation.org:

https://www.nwf.org/Educational-Resources/Wildlife-Guide/Birds/Bald-Eagle#:~:text=Bald%20eagles%20are%20large%2C%20predatory,equipped%20with%20sharp%20black%20talons.

 

Wikipedia, Bald Eagle:  https://en.wikipedia.org/wiki/Bald_eagle

Journey North - Bald Eagle:

https://journeynorth.org/tm/eagle/VisionA.html

 

Avian Report, Baby Bald Eagles in the Nest: Hatching to Fledging:

https://avianreport.com/baby-bald-eagles/

BirdFact, Bald Eagle Nesting (All You Need To Know):

https://birdfact.com/articles/bald-eagle-nesting

Bird Watching HQ, THE 2 TYPES OF EAGLES FOUND IN BRITISH COLUMBIA! (2023):    https://birdwatchinghq.com/eagles-in-british-columbia/

1994 Report, "Status of the Bald Eagle in British Columbia” published by BC Government Ministry of Environment, Lands and Parks,https://a100.gov.bc.ca/pub/eirs/finishDownloadDocument.do;jsessionid=3CA6C9B2E6A0C288D73D973F8B3D7E8D?subdocumentId=1194

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