Scientists Rule Out Radioactivity in Embryo Deaths
ORLANDO, Fla. (AP) _ Scientists believe a fish kill, acid rain and unusually warm, wet weather may be responsible for a decline in American bald eagle hatchlings last spring.
They have ruled out radioactivity as a possible cause of death for 40 embryos that failed to hatch after the eggs were collected from nests in Florida.
Radioactivity had been suspected when California experts reported that 49 bird species produced 65 percent fewer hatchlings after radioactive clouds from the Chernobyl nuclear disaster in the Soviet Union passed overhead last year.
The eagles’ lower birth rate caused concern since Florida is home to about 400 pairs of North America’s breeding population of bald eagles, about 90 percent of the total.
The director of an Oklahoma bird research center, Steve Sherrod, said last week that radioactive tests on the eggshells were canceled because an earlier study had found that radioactivity did not affect the nesting habits of swallows.
Also, federal Environmental Protection Agency tests showed that radioactivity was low in Florida before and during the nesting periods, he said.
A remaining hypothesis for the decline in births is that it was caused by a one-time occurrence, possibly involving a fish kill.
Eagle parents could have picked up bacteria from dead fish in their talons while transporting the food to the nests, Sherrod said. The warm, moist environment in the nests could have promoted growth of the bacteria, which invaded the eggs, he said. Acid rain could have contributed to the bacterial breeding conditions.
But scientists are still trying to find out why the eggs’ natural defenses against infection failed.
The Sutton Avian Research Center in Bartlesville, Okla., is conducting a three-year study with the University of Florida involving the transfer of eagle eggs to Oklahoma for hatching and release.
The bacteria were found this spring when 23 of 35 eggs shipped to Oklahoma failed to hatch.