Researchers put radio tags on more than 2,000 bobwhites from 2002-2008 to discern specific causes of death in the birds. Predation is usually the cause of bobwhites' demise, but from October to March, hunting was to blame for almost half of the dead quail. Annually, 40 percent of the deaths were due to harvesting in the four heavily harvested zones, in contrast with only 8 percent in the fifth, lightly harvested zone. "The three different approaches used in the study lead to the same conclusion," said Virginie Rolland, the UF Wildlife Ecology and Conservation postdoctoral researcher who led the study. "And that was that hunting has had a substantial impact on winter survival." But Rolland and a co-author of the research paper, Franklin Percival, who leads the UF-based Florida Cooperative Fish and Wildlife Research Unit, stressed that when it comes to assessing a species' health, many factors, such as predation and habitat quality, are often at play, and pointing blame at just one of them doesn't work.