When People Moved Less, Birds Moved More

Lockdowns may have altered bird behavior, study finds.

Barn Swallow Perching On Wooden Pole
Barn swallows were reported more often closer to roads. Rofique Hussain / EyeEm / Getty Images

Like so many other wildlife species, most birds became more active during the pandemic as people moved about less.

In a new study, researchers found that 80% of bird species studied were spotted in greater numbers in areas with the least activity. Sixty-six out of 82 species changed where they were located during the pandemic.

For the project, scientists compared observations from the United States and Canada on eBird, the online citizen scientist repository for bird-watching observations run by the Cornell Lab of Ornithology. They targeted areas within about 62 miles (100 kilometers) of major roads, urban areas, and airports.

“In some cases birds changed how they used all of the USA and Canada during their migration period, by spending more time in counties with stronger lockdowns, and in other cases birds used city landscapes differently than before the pandemic,” study senior author Nicola Koper from the University of Manitoba in Canada tells Treehugger.

“They increased their use of habitat within tens of kilometers of highways and airports—so we’re talking about really large-scale changes in habitat use.”

In June of 2020, a group of scientists coined the term “anthropause” in the journal Nature Ecology & Evolution “to refer specifically to a considerable global slowing of modern human activities, notably travel.”

In this new study, researchers refer to the anthropause and its potential impact on species. A significant drop in vehicle traffic resulted in decreased air pollution, less noise from human activity, and an increased risk of wildlife collision as more animals were moving.

Birds, they say, may have benefitted from less traffic because roads typically have a negative impact on them. However, some birds benefit from anthropogenic noise which helps ward off predators and reduce competition for food.

Birds That Moved More (and Less)

Red Tailed Hawk
Red-tail hawk sighting decreased, likely because there was less roadkill. sunmallia photography / Getty Images

For the study, researchers analyzed records of more than 4.3 million eBird observed by citizen scientists from March to May 2017–2020 of 82 bird species from throughout the U.S. and Canada.

They filtered the reports so that they had the same characteristics, including location and the level of birdwatcher effort. Their findings were published in the journal Science Advances.

Specific species caught their attention for increased reported activity.

Bald eagles are amazing because they are, well, bald eagles, and we are all in awe of them! Bald eagles changed their migration patterns so that they actually moved from counties with weaker lockdowns into counties with the greatest decreases in traffic,” Koper says.

Researchers found that ruby-throated hummingbirds were three times more likely to be spotted within .6 miles (1 kilometer) of airports than pre-pandemic. Barn swallows were also reported more frequently within a kilometer of roads than they were before the pandemic.

American robins are really cool, too, because they are so common that I think we’ve all assumed that they are pretty resilient to human disturbance, but we found that when traffic decreased during the pandemic, robins increased in abundance in all sorts of places—they increased in cities and within many kilometers of highways, for example. I think this lets us know that even common birds are actually much more sensitive to disturbance from human traffic and activity than we’d realized.”

Interestingly, in some incidents, fewer birds were spotted than normal. The number of birds actually decreased rather than increased when vehicle traffic dropped.

“For example, red-tailed hawks decreased near roads during the pandemic, in comparison with previous years,” Koper says. “Perhaps this is because there was less roadkill during the pandemic—some research in Maine suggests that this was the case—so red-tailed hawks didn’t find as much free food, or ‘supplemental’ food, near roads during the pandemic.”

Helping Conservation Efforts

There’s another element that could have played a part in the observations. During the past year-plus when things have been quieter and more people have been moving about less, plenty of people have been outside more. So they could pay more attention to birds and other wildlife that they might not have noticed so easily before.

“Actually other research has indeed shown that birders changed their behaviour during lockdowns, travelling less and closer to home. So the very first thing we had to figure out in our analyses was how to account for this,” Koper says.

“We did so by making sure that we were comparing bird observations from the same locations before and during the pandemic, and to only use bird surveys with similar characteristics before and during the pandemic (such as their distance traveled and time spent during the surveys).”

Because the findings suggest that human activity has an impact on so many bird species in North America, the researchers say this information can be used to make spaces more attractive to birds.

“While the most important thing we need to do to help birds is to conserve and restore habitat, it would also be helpful, particularly in the shorter term, to decrease traffic and disturbance,” Koper says.

“We can do this by having more virtual meetings instead of flying to visit our colleagues in other offices, working from home more often than before the pandemic, and investing in public transportation. All of those would help biodiversity, decrease our carbon footprint, and save money at the same time.”

View Article Sources
  1. Schrimpf, Michael B., et al. "Reduced Human Activity During COVID-19 Alters Avian Land Use Across North America." Science Advances, vol. 7, no. 39, 2021, doi:10.1126/sciadv.abf5073

  2. Rutz, Christian, et al. "COVID-19 Lockdown Allows Researchers to Quantify the Effects of Human Activity on Wildlife." Nature Ecology & Evolution, vol. 4, no. 9, 2020, pp. 1156-1159., doi:10.1038/s41559-020-1237-z

  3. "Lockdowns & Less Travel May Have Altered the Behavior of Birds." eBird, 2021.

  4. study senior author Nicola Koper from the University of Manitoba in Canada