CHICAGO, Illinois, October 31, 2002 (ENS) - The West Nile virus has decimated populations of chickadees around Chicago, Illinois, a new study shows. A team of 74 trained monitors throughout the six county Chicago region found that the black-capped chickadee, a once common bird, appears to have been extirpated from large areas. This is the first study that focuses attention on the effect of West Nile disease on songbirds, and it raises questions about the effects of chemicals used to control mosquitoes.
Previous reports have focused on crows, blue jays, hawks and owls, but experts fear that there could be many other bird species whose populations are also suffering.
In three areas of the Chicago region - parts of eastern Lake County, some south suburbs, and a large area of northern Chicago and nearby suburbs - chickadees were almost all gone. Thirty trained volunteer monitors spent 101 hours searching 31 sites with good chickadee habitat and found just two of the tiny, gregarious birds.
The black capped chickadee may be declining in areas hit hard by West Nile virus. (Photo courtesy National Park Service) Judging from previous October data, more than 120 chickadee sightings would be expected for this level of effort at these sites. In all other areas surveyed, chickadee numbers were reported as low or average, ranging between one and 23 birds found per survey. A map of the areas where chickadees are missing mirrors a map showing concentrations of human cases of West Nile virus.
"These are impressive and troubling results," said Bird Conservation Network (BCN) census coordinator Lee Ramsey. "We are encouraging trained monitors to check their areas frequently and report data on all bird species."
Many observers reported having seen dead or ill chickadees in early August, when thousands of dead crows were being picked up by municipalities in this area. Early August was also the date many gave of their last sightings of chickadees in the area.
Study participants also commented on low numbers of many other bird species. At least 124 species of native birds are known to have been affected by the virus.
"We still don't know the fate of many of the birds that breed here in summer and which were preparing to migrate when the disease hit," said Judy Pollock, Audubon's project manager. "For example, one observer commented on the disappearance of red-headed woodpeckers from her property. Another threat to this declining species really concerns me. Illinois is at the population center for this bird, and its numbers are plummeting due to habitat loss."
While the mosquito season is now waning, and West Nile concerns will not be in the forefront until spring 2003, the National Audubon Society recommends weighing the needs of birds in developing next year's pest control strategies.
"The populations of many bird species are already suffering. We should plan so that next year we don't add further stress by unwise or excessive spraying of pesticides," said Stephen Packard, Audubon director for the Chicago region. "The spray kills fish and many species of insects, disrupting the chain of life that birds and we ourselves depend on.":
