Analysis of avian morbidity and mortality data in 2000 indicated:
American crow was the most sensitive species for avian morbidity/mortality surveillance. However, some areas, particularly those distant from NYC, did not have positive American crows, but only positive birds of other species.
Almost all of the positive birds were found singly and not as part of a mass die-off in a single time and place.
Approx. a third of positive birds had signs of trauma on necropsy.
Many positive birds did not have pathology indicative of West Nile infection on necropsy. No lesions are pathognomonic for WN virus infection.
Positive dead birds usually provided the earliest indication of viral activity in an area.
Detection of positive dead birds always preceeded reporting of human cases.
Counties with human cases tended to have high dead bird surveillance indices, both West Nile positive and sightings.
<Maybe just the weaker and elderly birds are dying just like with humans. The trauma to the birds probably happens when they fall off a branch when they die.
What kind of trauma, exactly? Anything consistent with having been caught and let loose again?