Downtown falcon chicks' deaths linked to bacteria

A bacterial infection killed the baby peregrine falcons that hatched atop the Washington Mutual Tower in downtown Seattle during the spring.

Scientists at the Washington Animal Disease Diagnostic Laboratory at Washington State University performed a necropsy on two of the three young birds and found their brains had been attacked by a type of bacteria called mycoplasma, said veterinarian Lindsay Oaks, the lab's head of microbiology.

Mycoplasmas are very common bugs, and most animals — including humans — carry them, Oaks said. Normally harmless, mycoplasmas can proliferate and cause serious infections under certain conditions, such as when an animal is stressed, Oaks said.

"Maybe for some reason the chicks were exposed to it at just the wrong time or in the wrong amount," he said. "Maybe they were cold, or just unlucky. It's all pure speculation."

The parent birds most likely passed the bacteria to their offspring, Oaks said.

In people, mycoplasma can cause a respiratory infection called walking pneumonia.

Researchers are doing additional DNA testing to determine the strain of the bacteria that infected the falcons. Preliminary tests indicate it could be a species that hasn't been described before, Oaks said.

The chicks were more than 2 weeks old when they began to weaken and die one by one in early June.

Bird lovers watched the sad saga play out via a video feed shown live in the first-floor bank lobby of Seattle's second-tallest skyscraper. Peregrine falcons have nested on the 772-foot-tall building on and off since 1994.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com