Geographic Range
        Bald eagles (
        
         Haliaeetus leucocephalus
        
        ) are found throughout North America, near large water sources. These birds are native
            to Canada, the United States, portions of Mexico and several islands including Saint
            Pierre and Miquelon. Populations are especially concentrated in Florida, Alaska, the
            Pacific Northwest and near some rivers and lakes in the Midwest. Populations may be
            limited in Mexico, Arizona, New Mexico, Rhode Island and Vermont. These birds may
            be vagrants in Belize, Bermuda, Puerto Rico and the Virgin Islands; likewise, there
            have been reports of bald eagle sightings in Ireland, Sweden, Siberia, Greenland and
            northeastern Asia.
        
Habitat
        Bald eagles typically prefer areas near large water bodies such as sea coasts, coastal
            estuaries and inland lakes and rivers, in many areas, these birds are found within
            3 km of a water source. Although their specific habitats may vary depending on their
            range, habitat selection depends largely on prey availability, the availability of
            tall trees and the degree of human disturbance. These birds avoid human recreation
            areas, bald eagles will even forgo feeding if their foraging area is being disturbed
            by humans. Although food availability is important to habitat selection, bald eagles
            will inhabit areas further from foraging grounds to avoid human interaction. Most
            populations, specifically those in northern regions, migrate to southern, milder climates
            annually. Generally, these birds nest in the canopy of tall, coniferous trees, surrounded
            by smaller trees, however, in southern Florida, mangroves are used instead, they have
            also been reported nesting on the ground, on cliffs, on cellular phone towers, on
            electrical poles and in artificial nesting towers.  In the Chesapeake Bay area, these
            birds often roost in oak trees (
        
         Quercus
        
        ) and yellow poplars (
        
         Liriodendron tulipifera
        
        ), generally in woodlots with good canopy cover; however, their large body size prevents
            their movement through closed canopies. Due to food availability, these birds may
            also be spotted near dams and landfills.
        
- Habitat Regions
- temperate
- Aquatic Biomes
- lakes and ponds
- rivers and streams
- coastal
- Other Habitat Features
- estuarine
Physical Description
        These iconic birds go through 4 distinct maturation stages, each comprising one year
            of their life. Immediately after hatching, bald eagles have dark eyes, with pink legs
            and skin and flesh colored talons, their skin darkens to a bluish hue and their legs
            become yellow within the first 18 to 22 days of their life. Throughout their first
            year, their bodies, eyes and beaks are dark brown, although their underwing coverts
            and axillaries are white. In their 2nd year, their eyes lighten, becoming grayish-brown,
            they develop a light colored superciliary line and their body becomes mottled white.
            During their 3rd year, their bills and eyes begin to turn yellow and the coloration
            of their head feathers lighten, although their body remains mottled. In their 4th
            year, their body becomes mostly dark and their head and tail become mostly white,
            with some beige around their eyes and crown and isolated dark spots on their tail.
            Finally, mature coloration is reached in their 5th year. Immature bald eagles are
            often confused with
        
         golden eagles
        
        due to their dark coloration.  These birds can be differentiated based on the blotchy
            white coloration found on the underwing coverts, axillaries and tails of immature
            bald eagles; likewise, bald eagles have longer heads and shorter tails.
        
        Adult bald eagles are extremely large birds with characteristically yellow eyes and
            bills, white heads and tails and dark brown bodies, which may appear almost black.
            Although these birds obtain their adult plumage during their 5th year, they may continue
            to have a few dark spots on their head and tail for several additional years. Bald
            eagles have sexually monomorphic plumage coloration, although females generally have
            a somewhat larger body size. These birds have extremely large, powerful bodies; generally
            their plank-like wings have a span of 178 to 229 cm, their bodies are 79 to 94 cm
            long and they weigh about 4.3 kg. Their plumage alone weighs about 700 grams, which
            is twice as much as their skeleton, if lost; their flight feathers may take 2 to 3
            years to replace. These birds also have large heads, necks, bills and feet with sharp
            talons.
        
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- female larger
Reproduction
        Bald eagles have a monogamous mating system. These birds are believed to mate for
            life, or until a pair member dies. Although they do not migrate with their mate, they
            perform extremely demonstrative displays when they come together for the breeding
            season. Bald eagles perform flight displays with their mates, swooping at each other.
            During their cart-wheel display, the birds clasp their feet in the air and spin as
            they plummet towards the ground, letting go before impact.
        
- Mating System
- monogamous
        Bald eagles begin breeding when they are 5 years old.  Males and females construct
            their nests together, about 1 to 3 months prior to egg laying. Bald eagle nests are
            composed of sticks and can be massive, as birds often reuse nests for consecutive
            years, continually adding to it each year. The largest bald eagle nest on record was
            found in Florida; it was used for 30 years and weighed 2 tons when it fell out of
            a tree. However, nests do not generally last that long, on average nests in southern
            Florida and Saskatchewan are used for 5 years and nests in Alaska are used an average
            of 13 years. Nest are generally located away from human settlements, near water in
            coniferous trees, but may also be found in mangrove trees, deciduous trees, on the
            ground, on cellular phone towers, on electrical poles, on cliffs and in artificial
            nesting towers, this varies based on the population’s location. Nesting dates vary
            regionally; in Florida, they begin nest building in September, in Ohio they begin
            in February and in Alaska they begin in January.
        
        Bald eagles typically produce 1 brood of 1 to 3 eggs per season; many of their eggs
            do not survive, although they may have replacement clutches if needed. These birds
            have a low fecundity, in California, bald eagles may produce up to 36 young in their
            lifetime, for males, this is significantly correlated to their body size. The timing
            of laying varies regionally. Eggs are incubated in Florida beginning in October and
            may last until April, whereas in Yellowstone, eggs are incubated from March until
            April. Populations located further north tend to have shorter breeding seasons and
            more synchronous nesting periods. Their eggs are round to oval and are generally whitish;
            individuals in higher latitudes often produce larger eggs. Regardless of their geographic
            location, eggs are generally incubated for about 35 days, followed by an 11 to 12
            week nestling period. Bald eagles are the largest semi-altricial birds in North America
            and weigh approximately 60 grams at hatching; they may gain up to 180 grams per day.
            Fledgling time varies geographically; these birds leave the nest when they are between
            8 and 14 weeks old, although they may remain dependent until they are 18 weeks old.
        
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
        Both parents care for their offspring, although a larger burden falls on the female.
            Eggs are brooded by females about 3 to 7 times more frequently than by males. Eggs
            are generally only exposed while the parents change positions or turn the eggs, usually
            for less than one minute at a time, but it may be longer in mild weather. During the
            nestling period, young are fed 4 to 5 times per day. Nestling young are brooded constantly
            until they are about 4 weeks old; females are present about 90% of that time, as opposed
            to 50% among males. Most of the food is brought to the nest by males during the first
            two weeks post-hatching; eventually females also provide much of the food. The age
            at fledging may vary geographically based on climate and food availability, but generally
            ranges between 8 and 14 weeks. Even after fledging, immature bald eagles may continue
            their dependency on their parents for an additional 4 to 11 weeks.
        
- Parental Investment
- altricial
- male parental care
- female parental care
- 
         
          pre-fertilization
         
         - provisioning
- protecting
 
- 
         
          pre-hatching/birth
         
         - 
           
            provisioning
           
           - male
- female
 
- 
           
            protecting
           
           - male
- female
 
 
- 
           
            provisioning
           
           
- 
         
          pre-weaning/fledging
         
         - 
           
            provisioning
           
           - male
- female
 
- 
           
            protecting
           
           - male
- female
 
 
- 
           
            provisioning
           
           
- 
         
          pre-independence
         
         - 
           
            provisioning
           
           - male
- female
 
- 
           
            protecting
           
           - male
- female
 
 
- 
           
            provisioning
           
           
- post-independence association with parents
Lifespan/Longevity
        Bald eagles are long-lived with low adult mortality rates, although many of their
            eggs do not survive. A study in Florida found that a year after fledging, immature
            bald eagles have a survival rate of 89% in rural habitats and 65 to 72% in suburban
            habitats. After their 1st year, birds have an annual survival rate of 84 to 90%, regardless
            of their habitat type. In northern California, adult birds tend to have a 90% annual
            survival rate. These birds have an estimated captive lifespan of 20 to 30 years, although
            one captive individual reportedly survived for 47 years. Among wild individuals, bald
            eagles in Yellowstone are estimated to have a 15.4 year life expectancy, whereas in
            Prince William Sound, wild eagles are expected to survive about 19 years, with no
            difference in male and female life spans. The oldest known bald eagle in the wild
            was found in Alaska and survived 28 years, in northern California, the oldest known
            eagle survived 22 years. Their deaths are often caused by anthropogenic factors such
            as electrocution, vehicle collisions, getting caught in legs traps and accidental
            poisoning. Natural causes of death include starvation, malnourishment, disease and
            trauma caused by violent weather.
        
Behavior
        The migratory behavior of bald eagles varies across their geographic ranges. For instance,
            some populations, such as those from Yellowstone, only migrate locally for increased
            foraging opportunities and many southern populations do not migrate at all. Migratory
            birds from Canadian populations typically travel south to the United States during
            the winter, likewise, populations nesting in the Great Lakes region may move toward
            the Atlantic coast, down to the Chesapeake Bay and populations from northeastern United
            States and Canada may move south and inland, toward the Appalachian Mountains. Migratory
            birds congregate in areas with food abundances, specifically those areas below the
            freeze line with open water for hunting. Many populations use geographic landmarks
            for navigation, such as mountain ranges and rivers; the Mississippi River in particular
            is a major migratory corridor. Immature birds have much more erratic migratory paths
            and patterns. While migrating, birds generally soar, beginning in the late morning
            and go back to roosting before dark. Birds from the upper Midwest may travel anywhere
            from 6 to 151 days to reach their summer range and 15 to 77 days to reach their wintering
            range. Birds return to their nesting sites at varying times, as soon as weather allows.
        
        Bald eagles are often solitary, although they pair bond during the nesting season.
            However, groups of bald eagles may be seen in areas with ample prey and they may roost
            communally in large groups of up to 400 individuals. Their wings are powerful, although
            bald eagles often choose to soar using slow, heavy wing beats, which allow them to
            travel far distances. When walking, bald eagles are somewhat awkward, rocking their
            bodies as they move. A general time budget among bald eagles includes the percentage
            of time resting (91%), drinking (2.6%), scavenging (2.3%) and pirating food from others
            (1.8%). Generally, these birds are less active during the winter, or when winds are
            especially high, likewise, precipitation has a negative impact on their foraging success.
            During the breeding season, bald eagles become territorial; vocalizing or chasing
            conspecifics.
        
Home Range
        Their home range sizes may vary. For instance, populations in Oregon and Washington
            have home ranges of 6 to 47 km2, with an average of 22 km2; however, a population
            in Alaska has a territory radius of 0.5 km2, this is believed to be the lower limit
            for the species. On average, their home range size is believed to be 1 to 2 km2 and
            does not appear to oscillate between breeding and non-breeding seasons.
        
Communication and Perception
        Contrary to popular perception, bald eagles have relatively weak, high pitched, thin
            vocalizations, composed of chirps, whistles and harsh chatters. These birds produce
            3 main types of calls, a chatter, which sounds like ‘kwit, kwit, kwit, kwit, kee-kee-kee-kee-ker’,
            a wail and a peal, which is a long, high-pitched cry used when threats are perceived.
            In addition, these birds may communicate threats with a series of visual displays
            such as head motions, wing motions and crouching. Breeding pairs vocalize to each
            other when returning to their nest and have tremendous flying displays. With large,
            forward facing eyes, bald eagles likely have very good binocular vision. Although
            these birds do not have an adept sense of smell, they do avoid food items that taste
            spoiled.
        
Food Habits
        As opportunistic foragers, bald eagles have a fairly wide diet, but generally prefer
            fish. With such a large range, their diet may vary greatly. Bald eagles are known
            to eat the following fish:
        
         rainbow trout
        
        ,
        
         American eels
        
        ,
        
         gizzard shads
        
        ,
        
         white catfish
        
        ,
        
         kokanee salmon
        
        ,
        
         rock greenlings
        
        ,
        
         Pacific cod
        
        ,
        
         atka mackerel
        
        ,
        
         large mouth bass
        
        and
        
         chum salmon
        
        , among others. The speed of a river flow can greatly impact an eagles hunting success.
            These birds do not submerge themselves to obtain prey; instead, they use their strong
            talons to remove fish near the water surface. Another large component of their diet
            includes adult water birds, their nestlings and their eggs including
        
         common murres
        
        ,
        
         great blue herons
        
        ,
        
         snow geese
        
        ,
        
         Ross geese
        
        ,
        
         tundra swans
        
        ,
        
         northern fulmars
        
        ,
        
         auklets
        
        ,
        
         American coots
        
        and
        
         common loons
        
        . In the winter, their diets often shift to carrion and small mammal prey. Bald eagles
            may hunt live
        
         ground squirrels
        
        ,
        
         montane voles
        
        ,
        
         Norway rats
        
        and
        
         sea otter
        
        pups, among others. Likewise, these birds feed on the carrion of large mammals such
            as
        
         elk
        
        ,
        
         moose
        
        ,
        
         mule deer
        
        ,
        
         caribou
        
        ,
        
         bison
        
        ,
        
         wolves
        
        and
        
         arctic foxes
        
        . Populations of bald eagles have also been found residing near landfills, consuming
            human refuse. In addition to foraging by pursuing live prey or consuming carrion,
            these birds often pirate food from conspecifics and other raptor species, such as
        
         ospreys
        
        . In general, younger and smaller birds choose to hunt instead of pirate. When hunting,
            these birds perch and observe before descending on their prey and lifting it from
            the ground with their talons, however, when pirating food; eagles may fly, leap or
            walk to snatch the food. Regardless, bald eagles tend to forage much less when disturbed
            by humans, at times when humans are active in foraging areas, their feeding may be
            reduced by as much as 35%. For many populations, their arrival to their summering
            grounds marks a time of minimal food availability because many of the water sources
            may still be frozen. Fortunately, these birds can survive without food for several
            days. When food is available, bald eagles often gorge and store food in their crop
            for later digestion.
        
- Animal Foods
- birds
- mammals
- fish
- eggs
- carrion
Predation
        For some populations, bald eagles have few predators, allowing them to nest on the
            ground.  However, their eggs and young are often preyed upon by
        
         magpies
        
        ,
        
         gulls
        
        ,
        
         ravens
        
        ,
        
         crows
        
        ,
        
         black bears
        
        ,
        
         raccoon
        
        ,
        
         bobcats
        
        ,
        
         wolverines
        
        and
        
         arctic foxes
        
        . Fully grown adult birds are not often subject to predation.
        
Ecosystem Roles
        As a top predator, bald eagles impact all members of their trophic community. Their
            decline and recent population resurgence has impacted many other organisms, they are
            even causing a population decline in
        
         common murres
        
        . These birds have been found with
        
         Toxoplasma gondii
        
        as well as a
        
         protozoan
        
        , 2 genera of
        
         trematodes
        
        , 1 genus of
        
         acanthocephalan
        
        and 7 genera of
        
         nematodes
        
        .
        
- Toxoplasma gondii
- protozoans ( Protozoa )
- trematodes ( Trematoda )
- acanthocephalan ( Acanthocephala )
- nematodes ( Nematoda )
Economic Importance for Humans: Positive
        Bald eagles have been the national symbol of the United States since 1782. As a highly
            charismatic species, bald eagles draw bird watchers and other nature enthusiasts.
            In 1989, it was estimated that 20 to 30 million people are involved in bird watching
            activities, which may equate to approximately 20 billion dollars annually.
        
- Positive Impacts
- ecotourism
Economic Importance for Humans: Negative
        Bald eagles do not directly have a negative impact on humans. However, as a method
            of habitat management, buffer zones were established around their nesting sites, which
            limits human development in some areas.
        
Conservation Status
        The conservation status of bald eagles has shifted greatly during the recent past.
            As of June 28, 2007 these birds were removed from the protection of the Endangered
            Species Act where they had been listed since 1978. Their population was negatively
            impacted in the early and mid- 1900’s by hunting, habitat destruction and the use
            of insecticides, such as DDT. The Bald Eagle Protection Act was put into effect in
            1940, although their populations continued to decline throughout the 1950’s and 70’s.
            DDT’s fat soluble properties allow it to accumulate in the fats of organisms, because
            it biologically magnifies, top predators, such as bald eagles, were at great risk.
            DDT impacts all animals, with impacts such as deformities, neurological damage and
            in the case of birds, brittle egg shells and unhatching eggs. Fortunately, after the
            ban of DDT in 1972, their population has increased dramatically. In 1963, there were
            an estimated 417 pairs of bald eagles remaining in the continental US, as of 1998,
            there were 5,748 pairs, bringing their productivity back to levels seen prior to DDT
            usage. In addition, their population in Alaska as of 1993 was between 20 and 25,000
            individuals. In Washington State, these birds have had a 700% population increase
            from 1981 to 2005, growing approximately 9% annually. Other factors, such as guidelines
            regarding the proximity in which humans can develop near bald eagle nests have also
            positively impacted the species' population. Bald eagles are currently listed as a
            species of least concern according to the IUCN Red List of Threatened Species due
            to their increasing population and large range. Current and future threats to this
            species include contamination from coal power plants, Mercury poisoning and global
            climate change.
        
Additional Links
Contributors
Leila Siciliano Martina (author), Texas State University.
- Nearctic
- 
          living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.   
- native range
- 
          the area in which the animal is naturally found, the region in which it is endemic. 
- temperate
- 
          that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle). 
- forest
- 
          forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality. 
- mountains
- 
          This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation. 
- coastal
- 
          the nearshore aquatic habitats near a coast, or shoreline. 
- estuarine
- 
          an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity. 
- monogamous
- 
          Having one mate at a time. 
- iteroparous
- 
          offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes). 
- seasonal breeding
- 
          breeding is confined to a particular season 
- sexual
- 
          reproduction that includes combining the genetic contribution of two individuals, a male and a female 
- oviparous
- 
          reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body. 
- altricial
- 
          young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching. 
- male parental care
- 
          parental care is carried out by males 
- female parental care
- 
          parental care is carried out by females 
- arboreal
- 
          Referring to an animal that lives in trees; tree-climbing. 
- diurnal
- 
          - active during the day, 2. lasting for one day.
 
- motile
- 
          having the capacity to move from one place to another. 
- migratory
- 
          makes seasonal movements between breeding and wintering grounds 
- solitary
- 
          lives alone 
- visual
- 
          uses sight to communicate 
- acoustic
- 
          uses sound to communicate 
- carrion
- 
          flesh of dead animals. 
- ecotourism
- 
          humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals. 
- carnivore
- 
          an animal that mainly eats meat 
- piscivore
- 
          an animal that mainly eats fish 
- endothermic
- 
          animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds. 
- bilateral symmetry
- 
          having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria. 
- visual
- 
          uses sight to communicate 
- tactile
- 
          uses touch to communicate 
- acoustic
- 
          uses sound to communicate 
- chemical
- 
          uses smells or other chemicals to communicate 
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