COAST CITIES — Thirty years ago, crows were uncommon in much of San Diego.These days, a sea of black sometimes blankets the sky in Rancho Bernardo, Escondido and San Marcos neighborhoods. And the birds have even made their way to the coast, said Phil Pryde, past president of the San Diego Audubon Society.
“Early in the 1980s, it was rare to see crows south of Escondido — no more,” Pryde said.
Pryde explained that crows were drawn to San Diego by the rise in agriculture some 60 years ago. Later, they expanded into suburban and urban areas after discovering an abundance of plentiful food, ranging from scraps in trashcans to lawn grubs.
“They’re opportunistic omnivores,” Pryde said.
Crows are typically spotted en masse early in the morning and at dusk, because that’s when they feed. At night, they roost in large tree groves.
“It can be a little shocking to see so many crows flying overhead,” Pryde said.
Bird counts from the San Diego Audubon Society over the past three decades attest to the rise in crows. In 1985, a tally in Fairbanks Ranch as well as from Cardiff to Torrey Pines, among other areas, during a two-week period recorded 57 crows. In 2012, the same count tracked 1,632 crows.
Other county areas have seen a more significant increase. A 15-mile count centered along the Sweetwater River in San Diego jumped from six crows in 1985 to 5,436 in 2011.
Their growth can be attributed, in part, to their intelligence, Pryde said.
Crows have been observed dropping nuts in front of passing cars to crack them, for instance.
Cambridge University has released several studies, most recently this year, suggesting that crows stash food, and not just to have an excess supply in lean times. Often, they hide food because they feel that a rival is considering stealing it. The ability to anticipate competitors’ thoughts suggests smarts that few other creatures possess, the study states.
“Their intelligence means they can adapt to most environments,” Pryde said. “They learn through observation.”
Also, crows have few predators, according to Philip Unitt, curator of the Department of Birds and Mammals at the San Diego Natural History Museum. At one time, humans kept them in check.
“A hundred years ago, it was every young boy’s civic duty to shoot crows on the farm,” Unitt said.
He added that fewer people are farmers presently, so residents are less volatile toward crows. And while crows still pose some threat to San Diego’s agriculture scene, they don’t eat cash crops like avocados. Unitt said that in urban areas, crows can be a nuisance, but usually don’t bother residents.
Jenny Windle, communications and economic development programs manager for the city of San Marcos, said she hadn’t heard of any recent complaints related to crows.
The biggest threat to crows: West Nile Virus, which has hit crows on the East Coast especially hard.
For that reason, the county records crow, raven and jay deaths. They serve as an early sign of the disease’s presence in the community, according to Chris Conlan, supervising vector ecologist with the county.
So far this year in the county, five crows have died of West Nile Virus. But crows aren’t carriers of the disease; it’s nearly impossible for them to transmit West Nile Virus to humans, Conlan said.
Conlan noted that the county gets the occasional crow complaint. The most common reasons: crows eating crops and making noise outside of residents’ homes.
“We can’t do anything about those things,” he said.
He also noted that the county doesn’t try to control the crow population.
That’s due to a variety of state and federal protections afforded to them.