Birds took advantage of lockdowns by hanging out in the city, study finds
Dozens of species increased near roads and airports, birders’ observations show
Warblers, hummingbirds, hawks and other migratory birds across Canada and the U.S. hung out in cities during the pandemic lockdowns in the spring of 2020, treating urban-dwelling humans to far more visits than usual, a new study finds.
Birding is a hobby that surged in popularity during the COVID-19 pandemic. And many birders logged the species they sighted, and their locations, through "citizen science" apps such as eBird that allow data gathered by volunteers to be used by scientists for conservation research.
The new study by Canadian and U.S. researchers compared birders' observations on eBird between March and May in the three years before the pandemic to those same months during the 2020 lockdowns, which coincided with birds' spring migration. It was funded by a grant from the Natural Sciences and Engineering Research Council of Canada targeted at pandemic-related research.
Where the birds went
The researchers found big changes in which bird species in the study were spotted where. Of the 82 species tallied in the study, 66 of them changed abundance in counties where the level of traffic or human activity was altered. Most species increased in urban habitats, near major roads and airports and where there were stronger lockdowns, the study found.
"We also see with many species within cities themselves, that they moved from areas far from roads into areas closer to roads, for example," said Nicola Koper, a professor of conservation biology at the Natural Resources Institute at the University of Manitoba in Winnipeg. She's the senior author of the study, which also included researchers from Environment and Climate Change Canada, Cornell Lab of Ornithology, Carleton University in Ottawa and Dalhousie University in Halifax.
"That suggests that before the pandemic, a lot of birds were really being pushed out of the habitats that otherwise could have been suitable for them," she said, if it weren't for vehicle traffic and the noise and deadly collisions that come with it.
Bald eagles were one species that made very noticeable moves to counties with the biggest drops in traffic, Koper said. "They migrated in it using a different pattern in order to take advantage of the strongest lockdowns."
Sightings of ruby-throated hummingbird greatly increased near airports during the spring of 2020.
Another group that seemed to flock to urban areas during the lockdowns was warblers, which have seen very steep population declines since 1970. Koper said she spotted a blackpoll warbler in her backyard — a species she'd never seen before.
How to help birds post-pandemic
To Koper's surprise, even common species such as American robins spread into areas where they didn't previously live.
"Even the birds that are around us within cities are actually much more sensitive to human activity than we realized," she said. "So that means it's that much more important that we try to reduce our impact on the species we share the world with."
While the study showed that there were more birds in urban areas as a result of the pandemic, it didn't measure changes in their actual populations.
But Koper said having access to more habitat and resources during migration, which is a dangerous time for birds, likely had a positive impact.
She suggested that maintaining some lockdown habits — such as working from home more and driving and flying less — could reduce vehicle and air traffic and benefit both birds and humans.
"I think during the pandemic, we realized how much we depend ... in terms of our mental health on nature and green spaces and birds and wildlife around us, just to make sure that we have a good quality of life."
How pandemic data posed a challenge
Before the pandemic, one of the things Koper was researching was the impact of oil and gas infrastructure on birds. One of the challenges was distinguishing the impact of roads themselves on birds from that of traffic.
While out for a drive early in the pandemic, she says she was struck by how quiet it was and realized it was an opportunity to look at the impact of the traffic itself on birds.
While most of her previous work involved directly observing birds in the field, lockdowns made that impossible this time. So she turned to data on eBird, which she had been contributing to as a volunteer "for fun" for years.
One challenge was that people's birding habits also changed during the lockdowns — they tended to watch birds more from their backyards or balconies in the city compared with before, and there were a lot of new birders.
Researchers like Wesley Hochachka, a senior research associate at the Cornell Lab of Ornithology in Ithaca, N.Y., had already warned other scientists about how that changed the nature of eBird data compared with data from previous years.
Koper and her collaborators, including Hochachka's Cornell colleague Alison Johnston, did their best to account and correct for that by doing things like comparing the same locations before and during the pandemic and excluding records from new birders who didn't use eBird before the pandemic.
Hochachka, who is Canadian but wasn't involved in the new study, said in many cases, that had been done reasonably or very well, and he agrees that it looks like some species did increase in urban areas.
But he thinks with other species, it's possible they simply changed their behaviour, such as by singing more or hiding less, "so that they become more visible or more audible by human observers."
While scientists had already documented the way the pandemic affected individual species in certain areas, such as white-crowned sparrows and northern cardinals, Hochachka said the new study, by including 86 species across North America, shows just how widespread human impacts are.
He said more research is needed to really answer — and therefore find the solution — the key question that comes out of that: "What is it about human behaviour that might be making urban areas unsuitable for at least some bird species?"