During a span of five weeks last fall, more than four dozen owls were discovered sick or dead in pools, yards and public spaces across metropolitan Phoenix.
PHOENIX — The owls began showing up on Sept. 27th, 2024.
During a span of five weeks last fall, more than four dozen owls were discovered sick or dead across metropolitan Phoenix.
The baseball-sized flammulated owls – able to fly 300 miles in a day – were found in pools, yards, and public spaces. Seventeen of the 54 were dead, the rest suffering. In the end, just 13 of the owls survived.
The mystery of the 54 “flammies” has researchers at three universities working with the Arizona Game and Fish Department to determine just what happened.
Good Samaritans Turn in Owls Across Phoenix
John Bello found one of the owls. The assistant director of ASU’s Deer Valley Petroglyph Preserve in north Phoenix, Bello found the owl near a patio when he began his shift at work one morning in October 2024. The curious-looking owl was dead but had no visible injuries. Bello sent a photo of the small carcass to his friend, a veterinary anatomic pathologist.
“He said to immediately put it on ice and preserve it,” Bello said.
That pathologist is Jason Struthers, professor at Midwestern University’s Animal Health Institute in Glendale.
Struthers, a member of several Audubon societies, had already gotten word from two local bird sanctuaries about a spate of flammulated owls being turned into them by good Samaritans.
“People were so concerned of this unique-looking creature,” Struthers said.
Struthers said these “citizen scientists” found owls as far east as Apache Junction and as far west as Buckeye. Their decision to contact bird sanctuaries and transport the owls, both dead and alive, made possible a comprehensive study of a lesser-known owl species.
“I really want to emphasize, there are 17 people that found a dead owl, and they took that dead owl and they drove many miles to get to a rehab center,” he said. “That, to me, is the most impressive thing.”
Fall Heat Wave is a Possible Cause
Fifty-four flammulated owls is a lot, compared to the previous two years. The local sanctuaries that rehab injured birds, Wild at Heart and Liberty Wildlife, reported nine owls of the same species submitted to them in 2023 and three in 2022.
Struthers and Midwestern research assistant Hannah Brosius separated the organs of the 41 carcasses, examined tissues and conducted toxicology tests. Preliminary tests show the owls were eating well on their breeding range. Bird flu was ruled out.
Although testing is not complete, one likely cause of death is extreme heat. Phoenix experienced an unprecedented fall heatwave in 2024. Nearly all of the owls tested have kidney damage.
“That could mean they’re experiencing dehydration,” Struthers said. “The temperatures during those weeks were around 2.4 degrees Fahrenheit greater than the year prior, and even a more stark difference with the 2022 fall.”
Is Something Making Them More Susceptible?
If heat is determined to be the cause, it may demonstrate how even small changes in temperature can have debilitating effects on this species, considered a “sensitive species of concern” in North America.
“The idea is that the heat is playing potentially a big role. Obviously, that’s why we’re doing all this additional testing. Is there potentially an infectious disease that’s kind of making them more susceptible? Is there potentially some toxin making them more susceptible?” Struthers said.
As average temperatures in the Sonoran Desert continue to rise, the heat hypothesis would be more important, if confirmed.
“There are only about 12,000 flammulated owls. It is already a very low-population species,” he said.
Understanding the species
Other questions about the flammulated owl, like its migrating patterns and diet, may also be answered with the study.
Researchers at Northern Arizona University will examine the owls to determine everything they eat.
“We know they eat moths and grasshoppers and crickets and beetles. But there are other questions about their diet that are understudied,” Struthers said. “Do they eat small rodents, bats, songbirds? We don’t know.”
Struthers hopes more Arizonans take initiative to contact experts if they see something unusual in their environment.
“This is a reminder that even though you may not consider yourself a scientist by trade, you still can play the role of a scientist by providing little bits of data that other scientists who do this on a daily basis can use to better understand a species, better understand an environment,” Struthers said.