Scientists are focusing on Japan's Fukushima area after a study published this week found an alarming development at another nuclear disaster site -- Chernobyl.
The proportion of female birds has fallen off since the 1986 disaster at Chernobyl, the study found, and that appears to be causing male birds to increase their chirping in efforts to find a mate.
"The Chernobyl zone is a population sink, or an ecological trap, that brings in new birds each year but these birds suffer lower survival," co-author Tim Mousseau, a University of South Carolina biologist, told msnbc.com.
"In other words," he said, "the Chernobyl zone is not an eden for wildlife" as some have claimed.
Mousseau, who's leading a team along with Anders Pape Moller of the University of Paris-Sud, is now in the Fukushima area preparing to test birds there for radioactivity from the nuclear reactors hit by the tsunami after the March 11, 2011, earthquake.
"We will be placing small dosimeters on birds and measuring body content of radionuclides," he said. That will also be done this summer around Ukraine's Chernobyl area, where earlier testing focused on counting birds.
For the Chernobyl study "we collected 1,080 birds using mist nets in forested areas that were highly contaminated but also in areas that were effectively 'clean' and sites in between," Mousseau explained.
"In the more contaminated areas, most birds were yearlings, suggesting that survival rates were significantly lower in these areas than in clean ones."
"Sex ratios in the contaminated areas were significantly skewed towards males, reflecting higher mortality rates for females," he added. "In birds, females invest heavily in making large eggs, and these data suggest this investment comes at a cost of lower life span."
As for the chirping, "males in contaminated areas tend to sing more than in clean areas," Mousseau said, "presumably reflecting the greater challenges of attracting and acquiring a mate when sex ratios are skewed."
He's expecting even worse results at Fukushima.
A team did an initial survey last summer, counting 1,929 birds from among 45 species.
"Our expectation was that it would take many years and many generations of exposure for the cumulative effects" to show as they have in Chernobyl, Mousseau said.
"However, once we started our field work we realized that contamination levels were much higher than expected, even in July when we did our surveys," he said, "and it is likely that doses to these birds were very high in March and April when many of the birds were arriving to the area to initiate breeding."