Why are there so many crows in the Bay Area? It’s a question that comes up just about every year for the Golden Gate Audubon Society.
“Winter roosts of crows can be quite spectacular — or terrifying if you’ve watched too many Hitchcock movies,” said Glenn Phillips, executive director of the Berkeley-based organization.
He said he routinely encounters a large roost near the Fremont Street exit ramp off I-80 in San Francisco, as well as another near the Grand Lake Theatre in Oakland that’s been a popular gathering place for the crows for at least a decade. And while year-over-year data from the Golden Gate Audubon Society’s Christmas Bird Count has shown impressive growth in San Francisco’s crow population — the number of the birds observed here during the annual count has increased from nine to 1,520 in the last 40 years, noted Phillips — there’s a reason why you might be seeing so many in the coming months.
It’s simple: safety in numbers. In some cases, this is important during overnight roosting, as it’s less likely that the crows will be attacked by predators, such as red-tailed hawks or peregrine falcons, said Phillips. (It’s also worth mentioning that juvenile crows tend to stay with their parents for several years to take care of nestlings).
“When they’re gathered together in a flock like that, they’ll chase off a raptor in the area, making a lot of noise until it moves on,” he said. “And it’s not uncommon for birds to do this. American robins and Cedar waxwings also gather in flocks. But crows are so much more noticeable. They’re big. They’re noisy. And they’re relatively unafraid of people, so you can observe them easily.”
Their numbers might also appear more heavily concentrated during the winter as they seek out food resources.
“In the colder months, those resources tend to be more patchy,” said Phillips. “Having more eyes means they’re more likely to identify places where they can find food, or larger amounts of food in small areas.”
Crows are known for their intelligence and adaptability. They’re creatures of habits with a keen memory, and will often return to favorable roosting spots every winter. But Phillips also explained their transition to an urban area such as San Francisco is likely due to an abundance of food waste and garbage available for them to sift through.aside">
“They’re opportunistic foragers, and they’ll eat just about anything,” he said.
The downtown high-rises also provide an ideal environment for the birds because they not only offer safety from predators, but also shelter from the elements.
“Because crows are so well-adapted to human landscapes, what we’re doing is essentially subsidizing them. There are more crows because we’ve manipulated the city infrastructure in ways that work for us, but also work for them,” said Phillips.
Though people may have mixed feelings about the audacious and predatory birds, they’re here to stay — at least for a while. Most crows depart in the spring to nest and disperse into wider territory, which Phillips anticipates will happen in early March.
“While they can be a nuisance in large numbers, they won’t be here that long, so it’s a small price to pay for the privilege of getting to see these amazing creatures in action,” he said. “They’re very smart and fascinating to observe.”
And their numbers keep growing. Last year’s Christmas Bird Count in San Francisco tallied 1,520 crows — an increase from 738 crows in 2019 and 1,274 in 2018. New data will become available after this year’s count on Dec. 28.
“It’s pretty remarkable,” said Phillips. “And it’s definitely a statewide trend.”
Source : https://www.sfgate.com/local/article/Murders-of-crows-take-over-San-Francisco-Bay-Area-16667171.php1360