A total of 32 injured pelicans have been found on the coast between San Clemente and Huntington Beach over the past eight months.
Doctors suspect someone is behind the attacks.
"Lately, we've seen quite an increase that is making us suspicious that something is happening that may be intentional, that someone is harming these birds intentionally," said Dr. Elizabeth Wood, a veterinarian with the Wetlands and Wildlife Care Center.
The Wetlands and Wildlife Care Center says 22 of the pelicans have suffered compound fractures to their humerus.
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"It's very disturbing. The last one I think brought tears to both my eyes and Dr. Wood," said Debbie McGuire, executive director of the wildlife nonprofit.
Wood says the humerus in the animals is a very strong bone that needs plenty of force to break. When it is broken, the only chance of survival is emergency surgery as soon as possible.
"It's a really difficult battle, but we feel since there's a declining number of these birds in the wild, it's worth fighting for if it's a fresh wound," Wood said. "If the wound is older, we really don't have much of a chance, and unfortunately, we humanely euthanize those birds."
Wood says if there's a chance of releasing the birds, it would be after months of treatment and rehabilitation, which could cost as much as $100,000. The California Department of Fish and Wildlife is investigating.
Anyone with information can contact the CalTIP hotline at 888 334-2258.
The Associated Press contributed to this report.