You might want to keep your head up and your hat on if you walk down the 800 block of Richards Street (near Robson), where nesting crows have been attacking pedestrians since late April.

Or, you could carry an open umbrella — rain or shine — like Jim O'Leary does.

"I look a little funny but it's better than getting hit in the back of the head by a crow," said O' Leary, who works in the office building right beside the tree that contains the crows' nest.

"They do draw blood"

Many of his co-workers are regularly dive-bombed as they walk to work, says O' Leary, who hasn't been personally attacked ... yet.

Rowena Tansley hasn't been as lucky.

An homemade sign warns pedestrians of possible crow attacks in the 800 block of Richards Street. (Margaret Gallagher/CBC)

"I just heard a lot of cawing, somebody yelled at me to watch out," recalls Tansley. She now always pulls up her hood when approaching her office, as do many of her colleagues.

"They do draw blood," warns Tansley, as crows swoop down from power-lines, attacking passersby with alarming regularity.

Natural behavior

Even though the aggressive behaviour can seem right out of a Hitchcock movie, zoologist Wayne Goodey says the birds are just doing what comes naturally by protecting their vulnerable young.

"They're not doing this to upset people," said the UBC lecturer. "They're doing to it because historically it's been the best way to deter potential nest predators from their area."

Goodey says crows are amongst the most intelligent birds and have an ability to adapt and learn.

Aggressive swooping during nesting season is a natural behaviour crows use to protect their vulnerable young, said UBC zoologist Wayne Goodey. (Birdy206/Flickr)

"They have tremendously long memories," said Goodey. He says crows appear to remember a person who has yelled at or thrown things at them, and are far more likely to attack that person than a stranger — even two or three years after the initial encounter.

"You could say they hold grudges, in a sense," said Goodey. Crows don't attack every person that passes a nest, but merely resembling a perceived predator in terms of motion or appearance can elicit an attack.

Crows likely to return year after year

Crows are likely to return to the successful nests year after year, says Goodey. That's why O'Leary, Tansley and many of their coworkers would like to see the City of Vancouver do something about the situation, which is not unique to this block, although there are no official statistics available from the city regarding aggressive crows.

Responding to an email query from CBC, staff wrote "The City does not remove any nests and nests with active eggs are protected under the BC Wildlife Act. Staff advise citizens to take an alternate route or use an umbrella."