Three Decade Wildlife Mystery Solved: International Investigation Discovers Bald Eagles’ Killer
May 05, · Although they primarily eat fish and carrion, bald eagles used to be considered marauders that preyed on chickens, lambs, and domestic livestock. Consequently, the large raptors were shot in an effort to eliminate a perceived threat. Coupled with the loss of nesting habitat, bald eagle populations declined. Humans are not yet known to be affected by vacuolar myelinopathy, although the study did successfully affect chickens with the toxin, and Wilde continues to test fish and waterfowl such as ducks and coots for the disease. For more on this research, read Mysterious Killer of Bald Eagles Finally Identified.
Bald eagleHaliaeetus leucocephalusthe only eagle solely native to North Americaand the national bird of the United States. The bald eagle is actually a sea eagle Haliaeetus species that commonly occurs inland along rivers and large lakes. The adult male is about 90 cm 36 inches long and has a wingspan of 2 metres 6. Females, which grow somewhat larger than males, may reach cm 43 inches in length and have a wingspan of 2.
Both sexes are dark brown, with a white head and tail. The bird is not actually bald; its name derives from the conspicuous appearance of its white-feathered head. The beakeyes, and feet are yellow. Nests are usually about 1. The two or three eggs laid within take slightly longer than a month to hatch.
Both parents share in the incubation and feeding of the young. The immature birds are brown with whitish tail and wing linings, but the pure white head and tail plumage do not appear until the birds are four to five years old.
Bald eagles pluck fish out of the water with their talons, and sometimes they follow seabirds as a means of locating fish. Bald eagles also rob ospreys of their fish.
Besides live fish, bald eagles also prey on other birds, small how to approach a roundabout with 3 lanes, snakes, turtles, and crabs, and they readily eat carrion.
Bald eagles may have numbered in the hundreds of thousands when they were declared the American national bird inbut their numbers steadily declined over the next two centuries owing to human activities and persecution. The birds were hunted for sport, for bounties offered by state and federal governments, and because they were thought to menace livestock.
In Alaskawhere eagles perched on fish traps and scared away the salmon an annoyance eventually overcome by fitting the traps with devices to discourage perchingAlaskan bounty hunters killed more thaneagles in the period — The U. By the early s, the number of bald eagles in the coterminous United States had dropped to fewer than nesting pairs.
By the late s, these measures had enabled the birds to replenish their numbers in the wild. The bald eagle was reclassified from endangered to threatened status inby which time there were an estimated 4, nesting pairs in the lower 48 states.
By the population had increased to more than 6, pairs, and in the bald eagle was removed from the U. Like all hawk s and eagle s, the bald eagle belongs to the family Accipitridae of the order Falconiformes. Bald eagle. Videos Images. Additional Info. More About Contributors Article History. Print Cite verified Cite. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
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See Article History. Alternative Titles: American bald eagle, Haliaeetus leucocephalus. Bald eagle Haliaeetus leucocephalus. Bald eagles Haliaeetus leucocephalus in Homer, Alaska. Study the migratory, predatory, and living habits of North American bald eagles. Bald eagles Haliaeetus leucocephalus flying, perching, and fishing in the Chilkat River valley of southern Alaska. Get a Britannica Premium subscription and gain access to exclusive content.
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Bald eagles pluck fish out of the water with their talons, and sometimes they follow seabirds as a means of locating fish. Bald eagles also rob ospreys of their fish. Besides live fish, bald eagles also prey on other birds, small mammals, snakes, turtles, and crabs, and they readily eat carrion. Bald eagles do not; balds are uniformly dark. As golden eaglets age, they maintain a much lighter, whiter head than bald eagle nestlings. As they age they attain their very distinctive "golden" nape from which their name derives and which is the most obvious difference in older age eaglets.
By University of Georgia March 28, Their deaths—and, later, the deaths of other waterfowl, amphibians, and fish—were the result of a neurological disease that caused holes to form in the white matter of their brains.
Field and laboratory research over nearly three decades has established the primary clues needed to solve this wildlife mystery: Eagle and waterfowl deaths occur in late fall and winter within reservoirs with excess invasive aquatic weeds, and birds can die within five days after arrival. Now, after years spent identifying a new toxic blue-green algal cyanobacteria species and isolating the toxic compound, an interdisciplinary research group from the University of Georgia and international collaborators have confirmed the structure of this toxin.
The results were recently published in the journal Science. Credit: UGA. The cyanobacteria grows on the leaves of an invasive water plant, Hydrilla verticillata, under specific conditions: in manmade lakes when bromide is present. The bacteria—and animal deaths from the disease it causes—has been documented in watersheds across the southeastern United States.
In some animals, such as birds, turtles, salamanders and even a beaver, the disease manifests as erratic movements or convulsions. Wilde and Warnell graduate students studying the cyanobacteria have compiled maps and a list of affected watersheds. The invasive water plant Hydrilla verticillata can be found in many human-made lakes across the Southeast.
Wilde and others have been studying the cyanobacteria since , when bald eagles began dying in Georgia, South Carolina and North Carolina. But until recently, said professor Timo Niedermeyer of the Institute of Pharmacy at Martin Luther University Halle-Wittenberg in Germany, the origin of the brain-decimating disease was a mystery. Niedermeyer, who has worked with cyanobacteria natural products for years, wanted to help put the pieces together. He contacted Wilde and offered to collaborate. Samples of Hydrilla collected in the field were sent to him, and his lab cultivated the cyanobacteria in the laboratory and sent them back to UGA for further testing.
But the tests came back negative: The cyanobacteria from the lab did not induce the disease. Once again, he had colonized leaves sent to him from UGA. An image of Aetokthonos hydrillicola as seen through epi-fluorescence microscopy. While the cyanobacteria is virtually undetectable under a traditional microscope, the illuminated fluorescent light makes the cyanobacterial pigments glow and reveals its unique feathery shape.
He discovered a new substance that only occurs on the leaves where the cyanobacteria grows but is not produced in the cyanobacteria cultures. His investigations into the chemical structure of the isolated molecule revealed five bromine atoms. After almost a decade of testing the isolated molecule and collaboration between the labs in Germany and Georgia, they had their proof: the molecule does trigger vacuolar myelinopathy.
The neurological disease has not yet occurred in Europe, and no instance of the toxin-forming cyanobacterium has been reported.
Humans are not yet known to be affected by vacuolar myelinopathy, although the study did successfully affect chickens with the toxin, and Wilde continues to test fish and waterfowl such as ducks and coots for the disease. Phillips, Brigette N. Williams, James D. Lauderdale, H. Niedermeyer and Susan B. Wilde, 26 March , Science. DOI: Could this be what is making the dogs sick in the Texas Highland Lakes? Email address is optional. If provided, your email will not be published or shared.
The alarm bells began ringing when dozens of eagles were found dead near an Arkansas lake. More on SciTechDaily. B March 31, at am Reply. I was sure it was going to be Covid. It probably actually was Covid. Leave a comment Cancel reply Email address is optional.
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