WILDLIFE
Despite people's heroic rescue efforts in the aftermath of oil spills, few birds cleaned and released back into the wild survive more than one or two years.
That conclusion, reported by wildlife, fish and conservation biology professor Dan Anderson and his colleagues, supports a growing body of evidence indicating that rehabilitation techniques have not been effective in returning healthy birds to the wild.
The findings may lead to improved techniques for removing oil from birds and for handling and rehabilitating them. The work also may stimulate the development of better strategies for releasing rehabilitated birds back into the wild. Another possible outcome is rethinking the worthiness and cost-effectiveness of wildlife spill cleanups, or redirecting resources to protection or population restoration.
"Is there life after oil spills?" asks Anderson. "We're saying it's not working too well the way it's been done."
Using a combination of radio signals and special color markings, Anderson and his colleagues tracked 112 California brown pelicans that were cared for and released following oil spills in 1990 and 1991 off the coast of Southern California.
Two years after the 1990 spill, only 8 of the 91 rehabilitated pelicans (9 percent) could still be accounted for on the California coast compared to 10 of the 19 unexposed pelicans (53 percent) in the control group. The researchers found similar results for the fewer pelicans exposed to the 1991 spill. Tracking of all the birds ended in 1992.
Other studies, including some conducted by avian sciences
researcher Michael Fry, show that ingested petroleum products cause a number of physiological disruptions in birds and mammals, including anemia, immuno-suppression, additional stress-related phenomena such as endocrine dysfunction, reductions in nutritional status and internal lesions. The UC Davis study was not designed to separate the toxic effects of oil from the stress effects of handling the birds, which could also contribute to a lower survival rate.
"Cleanup efforts are demanded by the public; people will not just leave animals out there to die," says veterinarian Jonna Mazet, UC Davis-based director of the statewide Oiled Wildlife Care Network, a legislated program funded by state Fish and Game. "We want to protect and care for wildlife in the most professional manner possible. Advances in rehabilitation have been made since 1991. Research like this is giving us insight into what we can do to improve our efforts."
