Ice storms in Texas, smoke from Canadian wildfires billowing over much of North America, 31 consecutive days of 110-degree heat in Phoenix: Those have been just some of the swings in the weather this year.
How are the birds faring through it all?
It's too early to draw any confident conclusions from the data, scientists say. Maybe there were fewer sightings of birds in Phoenix during the heat wave, or maybe fewer people ventured outside to bird watch. Based on past data, however, researchers know that hot and cold spells have a negative effect on birds, especially hatchlings.
The Cornell Lab of Ornithology runs a program called NestWatch that enables volunteers to report what is going on in a nest: how many eggs, how many of them hatch, how many of the hatchlings eventually fly away.
Researchers Conor Taff of the Cornell Lab and J. Ryan Shipley of the Swiss Federal Institute for Forest, Snow and Landscape Research examined more than 300,000 breeding records for 24 North American species of birds from NestWatch and two similar programs, Project NestWatch in Canada and Project MartinWatch, which tracks young purple martins.
For each of the 300,000 nests in North America, Taff and Shipley looked up the weather records at that location, noting the hottest and coldest three-day stretches during the nesting period.
"When there's a particularly cold or a particularly hot period, does it impact your ability to successfully fledge nestlings?" Taff said.
The answer, in many cases, was yes. For 16 of the 24 species, a cold snap significantly reduced the number of hatchlings that made it out of the nest, by about 10 or 20%, Taff said.
When the weather is cold, insects are slow to emerge, leaving many birds with less food to bring back to the nest. "If it hits right at that really vulnerable stage, they don't do very well," Taff said.
The effect of heat waves was less pronounced, with 11 of the 24 species seeing a reduction in successful fledglings. With temperatures rising globally, many birds are nesting earlier in the spring when temperatures can fluctuate more wildly from warm to cold.
Future research could tie in data from eBird to more directly measure fledgling success rates and compare them with the size of local bird populations.
"You can potentially match that up with whether there was a cold snap or heat wave during the breeding season and whether that's affecting kind of the population level abundance," Taff said.
The paper also shows that there is much to learn about how the changing climate will affect birds. It's not even necessarily the extreme events like hurricanes or heat waves; more modest temperature shifts could also be deadly.
"They're obviously not good if they happen at a time that the birds are vulnerable," Taff said.
Fire impact on birds not lasting
Were/are the forest fires in Canada bad enough to impact fall and perhaps spring migration of songbirds?
Apparently not, according to Robert Zink, once professor of ornithology at the University of Minnesota, now in a similar position at the University of Nebraska.
"The fires have burned about 5% of the entire forest area of Canada," he wrote in an email responding to a question I asked.
"So, a 5% reduction in breeding grounds, and a similar reduction in migrating birds. I see a 5% short-term drop in population, no long-term effect.
"Passerine birds [songbirds] have enormous reproductive potential," he wrote. "Birds have survived millennia with fires, floods, cold summers, etc."
Zink made reference to a Minnesota mortality event that killed an estimated 1.5 million migrating Lapland longspurs in March 1904.
Dr. T.S. Roberts, author of "The Birds of Minnesota," the first complete study of birds found here, wrote in 1905 that the massive storm-related deaths of the longspurs produced no "diminution in the ranks."
"That is," Zink wrote, "in spite of the loss of millions they recovered in a year."
Roberts' interesting account of this event, published in the ornithological journal "The Auk" in 1907, can be found at sora.unm.edu/sites/default/files/journals/auk/v024n04/p0369-p0377.pdf
Lifelong birder Jim Williams can be reached at woodduck38@gmail.com.
