Since its introduction in 1999,West Nile virushas devastated aboriginal shuttle universe in North America . It spread across the continent in just five years , and it ’s been link to the last of millions of birds . But what ’s go on since ?
Researchers analyze 16 years of data on a quarter - million birds reveal that far more mintage were hit than we thought ; nearly one-half of the bird species they studied were negatively affect . And while one-half of those afflicted specie managed to rally within a yr or two , the other half have yet to recover . The finding are publish inProceedings of the National Academy of Sciencesthis week .
late analyses expose damaging effects of the virus in roughly one - one-fifth to one - third of the species examined . But these discipline relied on skirt numeration information that might have underestimated computer virus susceptibleness . enlisting and immigration , for example , could mask universe correct .
Now , to fully document the demographic impacts of West Nile computer virus across North American populations , UCLA’sRyan Harriganand co-worker analyzed mug - recapture data on 49 shuttlecock specie collected between 1992 and 2007 from over 500 snort - banding stations across the U.S. That method require you to get a hiss , band it , and then see it or catch it again . By calculate how many times you re - catch a bird over the course of migratory season , you may get a better estimation of the survival of the fittest rate for the population or species , Harrigan explained to IFLScience .
They found meaning declines in the survival of the fittest charge per unit of 23 of the 49 species enquire . That ’s 47 % . " Clearly we did n’t see the whole picture , " study coauthorJoseph LaMannafrom Washington University say in astatement . " Half the species we studied had significant die - offs . "
Among those 23 negatively affected species , there was a clear divide : boo that were only impacted during the disease ’s initial spread and those that still show no sign of recovery . Eleven species recovered to their pre - virus levels . These include the field true sparrow , fluffy woodpecker , blot towhee ( pictured above ) , and red - eyed vireo ( pictured above right ) . In fact , crows , jays , and other corvids – who were so powerfully associated with the disease on its arrival – seem to be some of the most springy ones .
For the remaining 12 species , mediocre survival of the fittest dropped and remain below pre - virus level in subsequent years . Swainson ’s thrush ( depict right ) , the purple finch and tufted titmouse may have suffer long - term population decline .
It ’s still unclear why some species do better than others . phyletic analyses , however , did identify the groups that were disproportionally affect by West Nile virus – New World dunnock , finch , and vireo – which suggest an evolutionary attribute to disease risk .
image in the textbook : Red - eyed Vireo ( top ) and Swainson ’s thrush . Both by Randy Korotev .
