WEST NILE VIRUS 1,
AMERICAN GOLDFINCH 0

In 1999, folks in New York State began finding unusually high numbers of dead birds--especially Blue Jays (below right) and crows. When birders and property owners submitted carcasses to health officials, laboratory analyses indicated the birds were carrying and apparently had succumbed to West Nile Virus, a pathogen previously unknown in North America. The virus, first described in 1937 from western Uganda, kept a rather low profile until outbreaks occurred among humans in Algeria (1994) and Romania (1996). Within three years the mosquito-borne virus made its way across the Atlantic Ocean--possibly via mosquitoes hitching rides on boats and planes or even thanks to humans or cage birds carrying the infection--eventually to be discovered in New York City in 1999. Since then medical studies have shown up to 80% of humans infected by West Nile Virus (WNV) are asymptomatic, while about 19% exhibit fever, headaches, muscle and joint pain, nausea, swollen lymph nodes, rashes, myalgia, and/or other symptoms.The remaining 1% or less acquire severe neurological problems such as the WNV versions of encephalitis, meningitis, and poliomyelitis--any of which can result in death. Curiously, the disease is 20 times more common among individuals older than 50 years.

Through late September nearly 4,000 WNV human cases had been reported just this year in all 48 contiguous states, with nearly 150 fatalities; this makes 2012 the worst year for WNV and people since 2003, undoubtedly because a warmer-than-normal winter followed by an unusually hot summer allowed infected mosquitoes to survive and propagate--one of the oft-overlooked downsides to global climate change. And just as more humans have been affected this year by the virus, beginning in early June in several states there was a sharp increase in WNV-related fatalities among birds.

All this brings us to an e-mail we got this week at Hilton Pond Center from Michael Wasilco (at left, with Black Bear cub), Regional Wildlife Manager for New York State Department of Environmental Conservation, Region 8. Mike writes: I am sending you details on a female American Goldfinch banded under your bird banding permit on 10 January 2009. This bird (#2510-94624) was found deceased 23 August 2012 in a Lyndonville yard in western New York State just south of the Lake Ontario shoreline. Because of several other bird deaths in this yard, the homeowner (Kevin Rogers) brought the bird to me to have it sent for testing. Mr. Rogers was concerned a new batch of bird seed he had purchased might be contaminated.

Although all state governments are not looking at West Nile Virus in birds and other wild animals, New York has an active monitoring program through the Department of Environmental Conservation's Wildlife Health Unit that, in turn, submits dead birds to Cornell University's Animal Health Diagnostic Center for testing. After Mike Wasilco handed over the American Goldfinch specimen, Cornell ran a "polymerase chain reaction" test (PCR) that looked for single strands of West Nile Virus RNA in serum from the bird's brain and kidney

All text, maps & photos © Hilton Pond Center

As noted in the final report from wildlife biologist Joe Okoniewski (above), the American Goldfinch was indeed a victim of West Nile Virus, which likely also killed the other birds in the homeowner's yard. The goldfinch, banded as an after-second-year female at Hilton Pond Center in 2009, was in her after-fifth-year when found dead this past August--and she was 596 straight-line-miles north at Lyndonville NY. A check of our records showed we had no recaptures of this particular bird at Hilton Pond after she was banded.

We can't know for sure whether "our" goldfinch acquired West Nile Virus on her southern wintering grounds or in New York State, but it seems unlikely a sick bird could have made a migratory flight of nearly 600 miles. In support of this conjecture, Mike Wasilco wrote in a subsequent e-mail to us that "this been a very active year for WNV both here in New York as well as across the nation. Since there were several other feeder birds that died in the same yard in the week or so leading up to this bird, I suspect they all got infected locally."

Mike also commented: "It was interesting to note the bird wintered in the South and summered up here, yet we have abundant goldfinches throughout winter here as well, likely breeders from even farther north?" We suspect American Goldfinches that show up here at Hilton Pond beginning in October may be facultative migrants that come south in years when winter weather is harsh and/or if there has been a failure of seed crops that normally sustain them during the cold. Historically there have been very few breeding records for American Goldfinches in South Carolina, but we have no doubt the species is expanding its range. For about the last decade we've a population of AMGO breeding at or near Hilton Pond Center, as shown by recent fledglings and females with brood patches we capture and band in late August and September. Nonetheless, our winter goldfinch population (males and females on thistle sock, above right) is far greater than in summer--a good sign those birds are from up north and just taking advantage of our southern hospitality during cold-weather months.

All text, maps & photos © Hilton Pond Center

All text, maps & photos © Hilton Pond Center

As evidence of migration we can mention seven American Goldfinches banded in winter at Hilton Pond and encountered March through September within what almost certainly was their northern breeding range. As noted on the map above, two showed up--captured and released by a bander--in Maryland (408 miles north), while another was found dead in far-off Maine (870 miles). Amazingly, the remaining four were encountered nearly 600 miles away within the same general area of New York State--and only about 120 miles apart! This is pretty good evidence many wintertime American Goldfinches we've been hosting at the Center's thistle and sunflower seed feeders had hatched from a nest somewhere just south of Lake Ontario.

All text, maps & photos © Hilton Pond Center

In the 13 years since West Nile Virus showed up in the continental U.S. countless birds have died from infection. Most affected have been the corvids, with animal epidemiologists concluding at least hundreds of thousands of crows perished nationwide--about one-third their total population! (Studies show that Maryland lost perhaps 45% of its crows, while the loss in the Baltimore-Washington DC area may have been as high as 90%. It's not clear whether those numbers include both American Crows and Fish Crows.) About a decade ago there also was a sudden decline in Blue Jays at many locations across the eastern U.S., a drop likely due to WNV. Other backyard birds apparently hit hard by the epidemic have been Back-capped and Carolina Chickadee (Carolina above), Eastern Tufted Titmouse, House Wren, Eastern Bluebird, and American Robin. Of all these, only Blue Jays and House Wrens seemed to make an early rebound across their ranges in about 2005--a rebound that may be negated by this year's bumper crop of mosquitoes carrying WNV. (NOTE: We've wondered whether a high incidence of West Nile Virus deaths among backyard birds that frequent feeders is actually a reflection of their being found more often by homeowners, but statistical analysis implies this is not the case.)

The good news: Just as many humans suffer no long-term effects from West Nile Virus, the same appears to be the case with birds. Blood samples from live birds of many species indicate they carry West Nile Virus but are not succumbing to it. This could indicate some individual birds have natural immunity to WNV, that they acquired immunity after a non-fatal bout with the disease, or even that the virus is mutating and becoming less deadly. (We've always speculated that because we do so much field work we've already had West Nile Virus and didn't even know it, but that could only be confirmed by biochemical tests that identify WNV antibodies in the bloodstream.) In any case, there's no question West Nile Virus still has potential both to harm humans and to decimate wild bird populations, so mosquito eradication programs are being stepped up in many locales.

All text, maps & photos © Hilton Pond Center
Mosquito photo courtesy Hans Smid

As a precaution when going outside in warm weather--almost year-round in the Deep South--one should probably put on bug spray; we prefer to wear clothing commercially pre-treated with insect repellent. Homeowners should also make a concerted effort to drain stagnant water from gutters, old buckets, and other containers, and to use recirculating pumps to keep things moving in water gardens. You might also follow the lead of the Evansville (Indiana) Audubon Society by constructing a couple of Chimney Swift towers to encourage these aerial insectivores to nest in your neighborhood and chow down on 'skeeters on-the-wing. By squelching local mosquito populations (Asian Tiger Mosquito, above) we may minimize fatalities in birds such as our American Goldfinch that flew 600 miles north from Hilton Pond, only to succumb to West Nile Virus on her breeding grounds in New York State.

All text, maps & photos © Hilton Pond Center

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