Pedestrians in Chicago have been warned not to venture too closely to the nest of two protective peregrine falcons who are raising their three chicks in the city.
Chuck Valauskas was struck by one of the falcons along Chicago’s busy Wacker Drive.
The patent lawyer was leaving work, walking below the nest situated on a seventh-floor ledge, when he felt a thud on his head.
“I thought, ‘What was that?’ It felt like a 16in softball,” Mr Valauskas told the Chicago Sun-Times.
He sustained a 1in (2.54-centimetre) gash on his head and now avoids the path beneath the nest altogether.
He has since had a tetanus shot to be safe.
At least one other person has been clobbered by the birds, building security guards said.
Building managers have put up two signs saying: “Warning! Beware of falcons. Parents will attack to protect babies on building ledge. Take a different path.”
From his window across from the nest on the 10th floor, Ruben Guardiola has been monitoring the falcons for a couple of weeks.
He noticed the raptors becoming aggressive with passers-by after their chicks hatched last week.
“Look at the building. It’s built for” birds, Mr Guardiola said.
“There’s no people, no predators.”
Falcons have been nesting every spring at the building since at least 2016, said Mary Hennen, who leads the peregrine programme at Chicago’s Field Museum.
The birds this year have nested low enough that they have become aggressive to humans walking below, she said.
Peregrine falcons can reach speeds in excess of 200mph when diving.
“It’s just a momma protecting her young,” Ms Hennen said.
“Their reflex is to swoop at you. That’s on purpose, to scare you.”
The falcons may leave in a few days or weeks, as soon as the chicks learn to fly, she said.
