Oil seals contaminated birds' fates.
Not Daniel W. Anderson, Brian E. Sharp, and their colleagues. Birds cleaned and released have short life spans and generally fail to breed, the scientists assert in two separate reports. Other researchers monitoring bird colonies had suspected this, but few had tracked birds to demonstrate it, says Anderson, a conservation biologist at the University of California, Davis.
Two years after oil spills in California in 1990 and 1991, only about 10 percent of the oiled brown pelicans that received treatment could be accounted for, compared to about 55 percent of breeding-age pelicans that avoided the oil, Anderson's team reports in the October Marine Pollution Bulletin. The team tracked 112 treated pelicans and 19 uncontaminated ones.
During the birds' 2- to 3-week treatment to combat exposure to the oil, Anderson's group marked all of them and attached radio transmitters to some. When released, the birds had a healthy body weight, blood chemistry, and plumage.
They also behaved normally. Many had even found mates while in captivity. These couples broke up after their release, however, and none of the birds bred, the authors report.
"We think they were immunosuppressed from ingesting the oil," causing subtle, long-term health problems, says Anderson. Earlier studies had shown that oil suppresses animals' immune systems, disrupts endocrine function, and damages organs. The stress of being handled during rehabilitation could also have contributed to the birds' early demise.
"We thought [the pelicans] had a good chance of surviving . . . they are pretty tough birds," says Anderson. However, "they are not as adaptable to stress as we thought."
Since studying the pelicans, Anderson's group has discovered that oil-contaminated coots, which live in marshes, fare no better after rehabilitation, even when released into a protected area.
Rehabilitated common murres, western grebes, and white-winged scoters had even less success than the coots or the pelicans. They lived a median of 6 to 11 days, reported Sharp in the April Ibis. Formerly with the U.S. Fish and Wildlife Service (FWS), Sharp is an independent ornithologist in Portland, Ore. Uncontaminated birds of these species captured for use in a variety of other studies survived a median of over 200 days after release.
Sharp examined recovery records kept by the FWS' bird-banding laboratory in Laurel, Md., for 127 North American seabirds contaminated with oil. The birds were cleaned, banded, and released between 1969 and 1994.
Despite the birds' short life spans, Anderson says he "wouldn't throw the towel in [on rehabilitation] at this point." He hopes the techniques can be improved, although he wonders whether the money involved in cleaning the birds could be spent in more efficient ways.
Sharp doesn't wonder. Rehabilitation for 800 birds and a few hundred sea otters after the Exxon Valdez oil spill cost $41 million, he points out (SN: 2/20/93, p. 126). Because of their great expense and poor success rates, such programs "cannot be considered as even partial restoration of damage," he says. The money should go to preventing oil spill damage "rather than focusing on ineffective attempts at rehabilitation after the damage has occurred."
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|Title Annotation:||Environment; birds cleaned of oil and released have shorter lives than birds not exposed to oil, and they usually fail to breed|
|Article Type:||Brief Article|
|Date:||Nov 16, 1996|
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