Federal documents show a University of Florida research unit killed more than 150 birds in the past 10 years to protect plant science work.

The Gainesville Sun  reported Sunday that the U.S. Fish and Wildlife Service documents show that 47 of the birds killed by gunfire were sandhill cranes and 105 were ring-billed gulls.

The sandhill is designated by the state as a threatened species. The gulls are not considered endangered or threatened.

The university's Plant Science Research and Education Unit allows researchers to study new crops and growing techniques. Projects at the unit include crops like citrus, watermelon and peanuts.

Officials say the cranes and gulls had damaged or eaten crops growing for research. The university is working on new non-lethal techniques to keep the birds away.

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