As many Westerners awoke this week to a sky so muted by smoke from raging wildfires that it looked like night, backyard bird watchers noticed something else: Silence at their bird feeders. Or worse yet, dead birds.
"I live in Folsom—have not seen a bird or heard a bird chirp this morning," said Jodi Root, a member of the California Birding group on Facebook.
"We live in northern Nevada and have noticed the same thing," added Karen Holden of Gardnerville.
"Same here in Napa," said Tammy Saunders "very quiet which just adds to the eeriness of the orange colored dark sky."
And on it went. Nearly 100 serious birdwatchers from throughout California and parts of Nevada responded to an impromptu survey posted on the Facebook group. And the majority said they had observed a pronounced drop in the number of birds flying in for a nibble at feeders or sips of water at bird baths, as well as a reduction in the variety of species.
So what is going on? Wild bird populations are already in major decline. But in recent weeks they have been subjected to smoke and extreme high temperatures that reached a crescendo on Wednesday, when an extraordinary upper atmospheric layer of smoke turned wide swaths of the California sky into palettes of orange and brown. The sky was so dramatic that former President Barack Obama tweeted a photograph of it to call out the need to address climate change.
Birds have highly sensitive respiratory systems—canaries were brought into coal mines in the early 20th century to detect the presence of toxic gases. Now the missing birds seem to be playing a similar role for a planet on fire. While not all that much is known about how birds respond to smoke, Andrew Stillman, a doctoral candidate at the University of Connecticut who studies birds in burned-out habitats, said this much is clear: Birds live on the edge, and extreme changes can have dire consequences.
Teasing out the answers can be complicated, because research on the long-term impacts of wildfire smoke on birds is severely lacking. But Olivia Sanderfoot, a researcher and doctoral candidate at the University of Washington, said the anecdotal evidence is overwhelming. "Overall, it seems like the anecdotes suggest that there is a decline in bird activity during smoke events," she said.
Stillman, whose work focuses not on smoke but on what happens to bird habitat in the Western United States after the embers have cooled, said there have been reports of dead birds being found in smoky areas, just as some California birders are finding dead hummingbirds in their backyards this week. "One thing that is important to point out is we do know high levels of smoke exposure can be harmful to birds," he said.
While studies have yet to nail exactly what killed these birds, the signs of stress are obvious.
Roger Lederer, emeritus professor of biological science at California State University in Chico, California, said he observes it every day when he sits in the backyard with his wife for cocktail hour. The California Towhees are puffed up, and walking around panting, the only way they can cool themselves, he said. Same with the scrub jays.
"All birds are stressed," Lederer said.
Stillman, who works with researcher Morgan Tingley at the University of California, Los Angeles, said that birds "cannot escape like humans by going indoors."
Birds are more at risk partly because of the way they are built: Their respiratory systems are more sensitive than those of humans, Lederer said. They do not have a diaphragm and "They are putting a lot more air through their lungs than we are," he said.
That sensitivity is why birds have served as harbingers for dangers in the atmosphere. Sanderfoot, in a 2017 literature review, "Air pollution impacts on avian species via inhalation exposure and associated outcomes," wrote that, "Birds have long been recognized as sentinel species for environmental change.'' She added that Rachel Carson's award-winning 1962 book, Silent Spring, "brought attention to the widespread impact of pesticide and insecticide applications on songbirds."
The 2017 paper by Sanderfoot and Tracey Holloway concluded, "Exposure to air pollution clearly causes respiratory distress in birds and increases their susceptibility torespiratory infection," as well as causing other problems such as affecting reproduction.
However, Sanderfoot, a fourth year doctoral student and National Science Foundation graduate research fellow at the University of Washington, said that her paper barely scratched the surface on how wildfire smoke impacts birds in the wild.
"We know pretty much nothing about the long-term impact of smoke on birds," she said.
Most of the research covers just a few species, many not living in the wild, and most focuses on air pollution, not wildfire smoke, she said.
"Of the roughly 10 000 species of birds known worldwide, only a few have been studied to characterize avian responses to air pollution, and the animals used in laboratory experiments may not be representative of the wild bird species most at risk from air pollution," Sanderfoot and Holloway wrote.
To find out more, Sanderfoot and her colleagues are now conducting studies throughout Washington, planting microphones and cameras in areas susceptible to wildfire smoke to determine if bird songs decrease when wildfire smoke is present. Her work builds on a Singapore study that used acoustical equipment to show that there was a decrease in bird sounds when it was smoky.
Tara Sears Lee, who volunteers at a nursery in Los Alto in California, is no scientist, but she observed the extreme impact of the heat and smoke in real time this week.
"Outside for 6 hours yesterday and no jays, crows, ravens, quail, turkeys, or hawks - all usual and very vocal visitors," she posted on Facebook. "Only hummingbirds, juncos, towhees and titmice. Worst of all was a dead hummingbird just lying on the ground - had heard they are being overcome by heat and smoke and just drop dead."
Other birders over the last week have posted photographs on Facebook of dead hummingbirds found in their backyards, and some have reported, paradoxically, seeing an increase in the number of birds at their feeders.
"I think all the birds came to my house south of San Jose. Sometimes there will be more than 40-50 out there," Charlotte Trethway Noriega wrote on Facebook.
Lederer is not surprised by either case. Migration can bring increases in bird visits to some neighborhoods and decreases in others, he said. And hummingbirds have a high metabolism and are less able to withstand extreme changes in conditions.
"I don't know if it's the smoke or the heat, but hummingbirds have been really stressed," Lederer said.
If there is any good news, he added, it is that the multiple fires in California—where more than 2.2 million acres have burned—came after fledglings had left their nests, and most probably escaped. And, the short-term stress on birds, as on humans, is likely to lift as the fires subside.
But unfortunately, Lederer noted, neither fires nor climate change are short term phenomena.
The bird population in North America has dropped by three billion—or 29 percent—since 1970, and a warming planet is changing the migration patterns of many bird species, according to a 2019 study published in Science. The study's lead author Ken Rosenberg, a senior scientist at the Cornell Lab of Ornithology, said in an article in Scientific America that the conversion of pastures and grasslands to cropland has reduced nesting places, and insects that many birds rely on for food are being killed by the wide use of pesticides.
As the planet gets warmer overall, Lederer said, many birds have adjusted their ranges farther north and started their migrations earlier than they did 30 years ago. If the trend continues, scientists believe that it won't be long before the Baltimore Oriole for example, will no longer be in Baltimore.
As for Stillman, who often tours scorched mountain sides while they are still smoking, he said he is finding signs of hope.
His research shows that birds, especially the black-backed woodpecker, seem to seek out and thrive in areas that have burned, feasting on the larvae of wood-boring beetles found in dying trees after a fire.
"They show up really fast," Stillman said, adding that when fire-scorched areas recover they are host to an incredible diversity of plants and birds.
"A burned forest is an amazing place to go birding," he said.
Stillman said his findings come with "a very big caveat": They may not hold for the new generation of so-called "mega" fires, like many of those that were started by lightning last month in California, which are extra destructive. He said he is studying "how are the birds responding to this new normal."
Deborah Petersen is a writer and editor living in the San Francisco Bay Area. She is the former Editor-in-Chief of the San Francisco Examiner and SF Weekly. And she, too, is a birder.