The refuge's staff captured birds using mist netting during two periods in June and August. They captured small forest birds, banded them, and took blood and oral swab specimens to determine exposure to the virus. All birds were released at the point of capture. A total of 243 birds from 18 species were captured. The diversity of the field sample was low compared to the existing bird population.

The sampling efforts were not designed to sample all birds within the refuge. Rather, the effort was aimed at sampling a portion of the bird population through time. Mammal trapping was carried out during the peak human epidemiological activity in Pennsylvania to better understand the exposure of mammals to the virus. At two locations on the refuge, mammals were trapped on four consecutive nights. Blood samples from small mammals were collected, after which all mammals were released at the point of capture.

The 2003 field season began a long-term mark-and-recapture study of the impacts of West Nile virus on small bird communities. After 55 years of activity in the Tinicum area, the virus is clearly well established and may be having an impact on local bird populations. The long term impact on the avian community can be confirmed by continuing the mark-recapture studies in concert with virus surveillance. Continued surveillance will allow for better estimates of risk and impact on the avian community structure. The mammal surveys suggest that exposure to the virus is not restricted to the avian community. What impact virus has on the local mammal community is not known.

The study was conducted in partnership with U.S. Department of Agriculture — Animal and Plant Health Inspection Service.