Monday, September 30, 2002 at 3:26 PM
Human cases of West Nile virus have been worrying public health officials this summer, but wildlife experts are equally concerned about its effect on birds. Owls and hawks began dying in Louisiana in July. Then the virus skipped to Ohio. Since August, more raptors have died in this state than anywhere else in the country and scientists don't know why. Many people who work closely with the sick birds have voiced concerns about what that massive die-off might mean for future populations. But scientists say that raptor numbers will most likely recover. ideastream's Karen Schaefer has more.
Karen Schaefer: Sick raptors first started showing up this August in Cincinatti. But it wasn’t long before bird rehabilitation centers around the state began reporting a sudden increase in the number of sick birds. In the Midwest official estimates are that a thousand raptors have died. Others put the death toll as high as four-thousand. Some places in Northern Ohio have been especially hard hit, among them a bird center in Castalia and the Medina Raptor Center near Spencer. Bill and Laura Jordan run the Medina facility, which is funded through private donations. Bill says this year, they’ve been almost overrun with sick owls, hawks, and other birds of prey.
Bill Jordan: Through this week, we’ve had 59 birds coming in with symptoms of West Nile virus. The survival rate on the ones we’ve taken in has been very low. We’re losing 70-80 percent of them, most within the first 72 hours.
KS: Bill says he believes survival rates in the wild are even lower. When the couple gets a bard owl or a red-tail hawk that’s sick, Laura Jordan says they have to move quickly.
Laura Jordan: Immediately we give fluids, because most of the birds - at least from the wild - they are coming in very dehydrated. And then after they survive the first three days - or if they survive the first three days, which many of them don’t - then we can move on into oral slurries which we create with a maximum calorie diet. We treat them for brain swelling…
KS: Even if the birds survive, many cannot be released back into the wild. Laura says brain injuries sustained while a bird is sick are often permanent, leaving the victim blind or unable to remember how to fly or hunt. This has worried many people who work closely with the birds, from operators of animal shelters to veterinarians like Dr. Patrick Redig. Dr. Redig is director of the Minnesota Raptor Center, one of the foremost raptor treatment and research facilities in the Midwest. He says, while the great birds of prey have been hardest hit, other bird species have also been affected.
Patrick Redig: I almost think of it like a wave front coming across the region and it was infecting all the different individuals of the species that are susceptible.
KS: Dr. Redig says surviving and unaffected birds will exhibit immunity to the disease, so he believes next year observers probably won’t see a repetition of this summer’s massive die-off. But he worries about what might happen to the ecological balance in areas where raptors deaths are highest.
PR: You can just imagine, I mean, if you take off a significant proportion of the top-level predators like this, there will be trickle-down ramifications through the entire food chain. You know, increases in the populations of prey species whether they be insects or rodents or things like that. But it’s all very speculative until we know what proportion of the population has been affected.
KS: Government scientists say there could be temporary upswing in the number of skunks next year, a favorite food of Great Horned Owls. But otherwise they don’t anticipate many ecological shifts. And they believe most species will recover their previous numbers, many within just a few breeding seasons. Kevin Metcalf is a hawk expert who works at the North Chagrin Reservation of Cleveland Metroparks.
Kevin Metcalf: Loss of living space is the biggest problem and pesticide uses of chemicals in agriculture. So West Nile is a minor concern relative to the other things that are happening.
KS: Lisa Smith of the Ohio Department of Natural Resources’ Division of Wildlife agrees that hawk and owl populations will recover. She points out that scientists are not yet certain it’s West Nile that’s responsible for this summer’s raptor deaths.
Lisa Smith: It appears that the birds have been exposed to West Nile virus, but I can’t over-emphasize the point that we do not know at this point that they have died as a result of West Nile virus. Unfortunately, if it is West Nile virus, there could be very little that we can do about it.
KS: Smith admits there is even some debate about what is spreading the virus. In addition to mosquitos, a flat fly parasite that’s peculiar to hawks and owls could be a carrier. Wildlife experts across the country are expressing concern about wild bird populations only just removed from endangered species lists - birds like the California condor, the peregrine falcon, and the American bald eagle. Fortunately so far, none of these species appears to be affected. Dr. Redig of Minnesota is working with other veterinarians to create a single-dose vaccine that could used to innoculate vulnerable populations and protect birds in captivity. They hope to have it ready this spring.
The promise of a vaccine brings some comfort to Bill and Laura Jordan, who continue to care for dozens birds they suspect have West Nile. And the Jordans say they’re rewarded every time they can return a healthy bird of prey to the wild.
No one knows yet what the final count of raptor deaths will be. Wildlife experts say the deaths will probably continue until after the first frost, although the number of new cases may taper off before then. And early next spring, when the first nestlings begin to hatch, scientists will be out checking to see how many birds are born. In Spencer, Karen Schaefer, 90.3.
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