A wildlife rescue group returned to San Francisco's Golden Gate Park on Wednesday to try to find and capture a red-tailed hawk that appears to have been shot in the head with a nail gun.

A rescuer with the Monterey-based group WildRescue and volunteers from the community combed the park's southwest corner, where the bird was spotted the previous evening with a nail extending from its cheek through the front of its head, said Rebecca Dmytryk, executive director of WildRescue.

"It's very time-consuming trying to find it," she said. "But it is in that general area."

When the bird was spotted on Tuesday evening, it was trying to eat a squirrel.

"It looked like he was having a hard time. He looked weak," Dmytryk said.

Crews tried to lure it into a trap but were unsuccessful. Rescuers cannot use nets because the nail could get caught on them and further injure the hawk.

Dmytryk said the bird appears to have been shot at close range. Her group was alerted to the injured animal on Sunday night.

Red-tailed hawks are protected under federal law and harming one is punishable by up to six months in jail and a $15,000 fine, according to Elise Traub, outreach and policy manager for the Humane Society of the United States' Wildlife Abuse Campaign.

Traub spoke to the San Francisco Examiner.

Sightings of the hawk can be reported to WildRescue at (831) 429-2323 or rescue(at)wildrescue.org.

The group is also offering a $5,000 reward for information leading to the arrest and conviction of whoever harmed the bird.