Bird populations near Japan's damaged Fukushima nuclear plant have dropped more than expected from a related analysis of the Chernobyl disaster, scientists say.

Researchers counting birds at 300 locations in Fukushima prefecture from 15 to 30 miles from the Fukushima nuclear power complex damaged in last year's earthquake and tsunami said they found bird communities were significantly diminished in the more contaminated areas.

They compared the findings to a similar study undertaken in Ukraine's Chernobyl Exclusion Zone from 2006 through 2009 and discovered that for 14 species of birds found in both locations, the decrease of population size was more pronounced at Fukushima than at Chernobyl, where a devastating nuclear power plant accident occurred in 1986.

The study suggests "these birds, which have never experienced radiation of this intensity before, may be especially sensitive to radioactive contaminants," co-author Timothy Mousseau, a biologist at the University of South Carolina, said.

The study suggests many similarities between the Chernobyl and Fukushima events and provides new insight into the first-generation effects of radiation exposure on animals in the wild, researchers said.

"Our results point to the need for more research to determine the underlying reasons for differences among species in sensitivity, both initially and following many generations of exposure," Mousseau said in a University of South Carolina release Tuesday.