The number of occupied territories within the study area, which is located within Yukon-Charley Rivers National Preserve, has shown a steady increase since the species neared extinction in the early 1970s because of nest failure caused by DDT contamination. In 2007, 50 occupied territories were observed, which is nearly a 5-fold increase since 1975.
Reproductive success has improved during the past 3 decades. The number of nestlings, though variable among years, has increased from 17 in 1975 to 82 in 2007. Recent evidence suggests that American Peregrine Falcons are still threatened by environmental contaminants, though. Analyses of Peregrine eggs from the upper Yukon River suggest that mercury levels are increasing. Mercury is a persistent compound which bioaccumulates at high trophic levels and causes toxic effects (similar to DDT). The amount of mercury being found in Yukon area eggs is currently at levels that may affect reproduction. High levels of mercury are made biologically available through industrial processes such as mining and waste incineration, and will likely increase with global industrialization. Additionally, DDT and other pesticides are still being used on Peregrine wintering grounds, which may cause continued risk to the population.
Each summer, Peregrine Falcon monitoring is conducted along 265 km (165 mi) of the Yukon River between Circle, Alaska, and the border of Yukon Territory, Canada. The basic approach follows guidelines established in the Monitoring Plan for the American Peregrine Falcon (US Fish and Wildlife Service 2003).
Collecting data on nesting territory occupancy, nesting success, and productivity requires two annual surveys conducted by boat along the upper Yukon River. All potential nesting territories along the river are observed from shoreline or islands using binoculars and spotting scopes. Observations are conducted for a minimum of 4 hours at each potential nesting territory.
Collecting data on environmental contaminants requires visiting nests using standard rock climbing techniques. During these visits, the number of young are counted, prey remains are checked, and unhatched eggs and feather samples are collected for analysis.
The protocol for this Vital Sign is not yet available
There are no data files currently associated with this Vital Sign. Most likely, the data
are being processed. When data are
available, there will be links to the data files and metadata here. Most data will be available from the
NPS IRMA Data Store