Finally, I read of a project in the October 2003 issue of the Wildlife Society Bulletin that may shed some light on the West Nile mortality question. Since the fall of 1997, a few researchers were studying social organization, dispersal patterns and cooperative nesting attempts of common (American) crows in and around Stillwater, Oklahoma. The crows were captured with a rocket net and marked with wing tags and colored leg bands. Family groups were marked and classified as breeders, auxiliaries which were offspring from previous years and individuals that had moved in with the families from other areas. Morphological data was taken from each individual before being released.

The crows were monitored continuously throughout the year from 1997 through 2002. Of importance for this article was that in August of 2002, 120 of 145 individual crows in approximately 28 family groups were marked. It was during the fall of 2002 that West Nile was first confirmed in the Stillwater area and in mid September a marked individual in the study died. In the next 30 days 8 more carcasses were found and 37 other marked crows were missing and presumed dead. Some of these were observed staggering clumsily prior to their disappearance.

Some of the individuals that disappeared during the fall of 2002 dispersed out of the population that is normal. Yet 40% (48 of 120 marked individuals) within 2 months of the arrival of the West Nile Virus in the area, died. One other observation was referred to in the article. In Ithaca, New York, 25 of 68 crows (37%) in 10 contiguous crow families disappeared between July and October 2002. 21 were found dead, and of these, 19 were known or suspected to have died from West Nile Virus.

These numbers of individuals are not great but the data suggests that mortality in wild crow populations may approach 40% within 2 months of exposure to the West Nile Virus.