Quantcast
Environmental News for a Healthier Planet and Life

Rat Poison Linked to Several Deaths of San Francisco’s Iconic Parrots

Animals
Rat Poison Linked to Several Deaths of San Francisco’s Iconic Parrots
A flock of parrots in Telegraph Hill, San Francisco. ~dgies / Flickr

Ask any resident of San Francisco about the waterfront parrots, and they will surely tell you a story of red-faced conures squawking or dive-bombing between building peaks. Ask a team of researchers from the University of Georgia, however, and they will tell you of a mysterious string of neurological poisonings impacting the naturalized flock for decades.


Bromethalin, a common rat poison, has been linked to the deaths of San Francisco's famous Telegraph Hill parrots. Publishing their multi-year research in PLOS ONE, the research team suggests that the odorless and potent rodenticide may be responsible for a neurological disease that presents itself with symptoms such as seizures and disorientation in at least three birds.

Since 1989, the well-established flock of three interbreeding species of red-faced parrots has expanded its range through San Francisco's waterfront, where they can be heard chirping from the treetops and soaring through the city's parks. For the last two decades, stories of neurological conditions affecting these parrots have been reported, prompting the City of San Francisco to prohibit the public from feeding the birds over concerns of inappropriate diets. Over time, cases grew with similar reported symptoms — between 2003 and 2018, a local bird rescue organization reported more than 150 neurologically affected parrots, roughly one-third of which had died as a result of associated complications.

That's when a team of veterinarians, pathologists and researchers stepped in. Together, they recognized that the symptoms were similar to those caused by the difficult-to-detect single-dose rodenticide known as bromethalin. This non-anticoagulant, single-dose toxin was first registered with the U.S. Environmental Protection Agency (EPA) in 1984 and was used to kill — with a single dose — rats who similarly experienced lethargy, weakness in their legs, paralysis and a lack of response to stimuli. Under a 2008 EPA mandate, bromethalin replaced other more potent rodenticides known to cause unintended poisoning in wildlife, resulting in a 65 percent increase in related cases in the following decade.

Between 2013 and 2017, researchers found evidence of the difficult-to-detect bromethalin and its active metabolite desmethyl-bromethalin in wild birds, ruling out another theory that suggested viruses, such as West Nile or toxoplasmosis, had caused the neurological side effects. Consistent lesions in the poisoned birds' central nervous system, samples from the livers and brains of dead birds, as well as high-performance chromatography — the separation of mixtures in fecal samples from live birds — further suggested bromethalin poisoning. In the three birds that died, bromethalin was detected in the brain and liver samples with all but one testing above the detection limit. It's possible the parrots don't metabolize the potent neurotoxin in the same way as other species and could be ingesting a sublethal dose — a potentially lethal amount when consumed in large enough increments.

Though the researchers aren't sure how the feral animals are being exposed to the rodenticide, they say that it is likely that other wild animals may also be within contact.

"The findings offer us an opportunity to assess the true risk of this rodenticide to pets and feral animals and to clarify the risk of potential soil and water contamination," said study author Fern Van Sant in a statement.

Study co-author Branson Ritchie said that their work helps researchers to "understand if this toxin is accumulating in a space where it could pose a health risk in other free-ranging animals, or, possibly, in companion animals and people."

A mass methane release could begin an irreversible path to full land-ice melt. NurPhoto / Contributor / Getty Images

By Peter Giger

The speed and scale of the response to COVID-19 by governments, businesses and individuals seems to provide hope that we can react to the climate change crisis in a similarly decisive manner - but history tells us that humans do not react to slow-moving and distant threats.

Read More Show Less

EcoWatch Daily Newsletter

Doug Emhoff, U.S. Vice President-elect Kamala Harris, Jill Biden and President-elect Joe Biden wave as they arrive on the East Front of the U.S. Capitol for the inauguration on Jan. 20, 2021 in Washington, DC. Joe Raedle / Getty Images

By John R. Platt

The period of the 45th presidency will go down as dark days for the United States — not just for the violent insurgency and impeachment that capped off Donald Trump's four years in office, but for every regressive action that came before.

Read More Show Less

Trending

A hazy Seattle skyline due to wildfire smoke is seen on September 11, 2020 in Seattle, Washington. Lindsey Wasson / Getty Images

Washington state residents are taking climate matters into their own hands. Beginning this month, 90 members of the public join the country's first climate assembly to develop pollution solutions, Crosscut reported.

Read More Show Less
Boletus mushrooms such as these are on the menu at ONA restaurant in Arès, France. Jarry / Tripelon / Gamma-Rapho / Getty Images)

For the first time ever, a vegan restaurant in France has been awarded a coveted Michelin star.

Read More Show Less
Samples of chocolate, strawberry and taro ice cream in the Chinese city of Tianjin tested positive for coronavirus. Alex Lau / Conde Nast via Getty Images

Ice cream samples in the Chinese municipality of Tianjin have tested positive for traces of the new coronavirus.

Read More Show Less