Bald Eagle Mortality Due to Bacterium

Susan Wilde has uncovered a bacterium, one with a powerful toxin that attacks waterfowl, hiding on the underside of hydrilla that grows nearly everywhere in the United States, including the Chesapeake Bay and its fresh tidal tributaries, such as the Potomac River.

After 20 years of testing, she determined that the bacterium had never before been recorded, and the brain lesions it causes in birds had never documented.  Wilde recently gave her discovery a name: Aetokthonos hydrillicola.  The Greek word means “eagle killer” for its ability to quickly kill the birds of prey.  It’s the latest threat to a raptor that is starting to flourish after being removed from the endangered species list.


Across the Southeast, near reservoirs full of invasive plants (hydrilla), eagles have been stricken by this bacterium, which goes straight to their brains.  Eagles prey on American coots, which dine almost exclusively on the plant and are being hit even harder.

Before now, reservoirs that serve up a buffet of this plant were considered beneficial because they helped fuel the annual migration of coots from Canada to Florida and beyond, while also feeding eagles.  But now the reservoirs are “death traps,” said Wilde, an assistant professor at the University of Georgia whose study of the topic was recently published in the journal Phytotaxa.  In Arkansas, Georgia, Florida, South Carolina and North Carolina, coots, shorebirds, ducks and eagles are dying by the dozens from the incurable lesions.

“We’re attracting them to places where they’re going to die, and that’s not a good thing,” Wilde said.


Eagles get top billing in the study because they’re the national symbol, arguably the most-recognized animal in America.  But the bacterium and its toxin is devastating to plant-loving coots.  The migration of coots is a spectacle that bird watchers flock to man-made reservoirs to see. Five thousand can descend at once on a single lake, noisy, splashing, feeding.

The only way to save the animals is to spend millions to eradicate a plant that was introduced to the United States in Florida about 60 years ago.  It now grows in virtually every body of fresh water.  It grows prolifically in the Chesapeake Bay region, which is also full of bald eagles and visiting coots, a dark, plump, duck-like bird with a bright orange dot for an eye.

Eagles don’t mess around when they dine on coots.  Even the head is fair game.  They leave nothing but the feet, Wilde said.  She theorized that the bacterium enters eagles while they’re munching on the guts of their prey.  “The only way we can tell a bird has it is they have a characteristic in the brain, a lesion,” she said.  “There’s no damage to any other part of the body.”

The eagle killer might hide on the underside of leaves because it prefers shade, but Wilde and her fellow researchers haven’t figured out why.  It radiates outward in a circle with strange edges and spikes.   “It looks like it would kill eagles,” she said.


Bald eagles were removed from the federal endangered species list only seven years ago.  They nearly went extinct when their habitat was clear cut in the past century, their prey (such as ducks) was over-hunted and a pesticide caused them to lay eggs with shells so thin their chicks couldn’t survive.   In 1978, they were listed as endangered in every state on the U.S. mainland but five, where they were listed as threatened.

Wilde and Brigette Haram, a doctoral student at the Warnell School of Forestry and Natural Resources where Wilde teaches, conducted lab trials on chickens and mallard ducks to better understand the toxin, and studied other birds that were brought in acting disoriented and sick.  “We haven’t seen a species that’s immune,” Wilde said.   So far, she’s only found it as far north as North Carolina.  Tests in Virginia and New York were negative.  She hasn’t tested in the Chesapeake Bay area, but it’s on her to-do list.

Source Article: