CHICAGO (AP) 鈥 A pair of peregrine falcon parents are raising three chicks along Chicago's busy Wacker Drive, and beware to any pedestrian who ventures too closely to their nest.

Just ask Chuck Valauskas, who was struck by one of the falcons. The patent attorney was leaving work one day last week, walking below the nest situated on a seventh-floor ledge when he felt a thud on his head.

鈥淚 thought, 鈥榃hat was that?鈥 It felt like a 16-inch softball,鈥 Valauskas told the Chicago Sun-Times.

He sustained a 1 inch (2.54-centimeter) gash on his head and now avoids the path beneath the nest altogether. Has has since gotten 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, 鈥淲arning! Beware of falcons. Parents will attack to protect babies on building ledge. Take a different path.鈥

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 passersby after their chicks hatched last week.

鈥淟ook at the building. It鈥檚 built for鈥 birds, Guardiola said. 鈥淭here鈥檚 no people, no predators.鈥

Falcons have been nesting every spring at the building since at least 2016, said Mary Hennen, who leads the peregrine program at Chicago's Field Museum.

The birds this year have nested low enough that they鈥檝e become aggressive to humans walking below, she said.

Peregrine falcons can reach speeds in excess of 200 mph (321.87 kilometers per hour) when diving.

鈥淚t鈥檚 just a momma protecting her young,鈥 Hennen said. 鈥淭heir reflex is to swoop at you. That鈥檚 on purpose, to scare you.鈥

The falcons may leave in a few days or weeks, as soon as the chicks learn to fly, she said.

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