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Peregrine Falcon: Central Alaska Network Resource Brief

Peregrine Falcon

Yukon-Charley Rivers

Peregrine Falcon Monitoring Status and Trends:

2007 marked the 32nd consecutive year of American Peregrine Falcons monitoring along the Upper Yukon River corridor. In late May 2007, biologists travelled the Yukon River between the communities of Eagle and Circle, Alaska, and counted the number of occupied Peregrine Falcon territories. A second survey was conducted in July to determine nest success and productivity. Both surveys indicate continued positive growth in the Yukon-Charley Rivers Peregrine Falcon population.

The number of occupied territories within the study area 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.

» Map:
YUCH
Peregrine
study area

» Graph:
# of occupied
& successful
territories

» Photo:
Peregrine
chicks

Reproductive success has improved during the past 3 decades as well. The number of nestlings, though variable among years, has increased from 17 in 1975, to 82 in 2007. However, recent evidence suggests that American Peregrine Falcons are still threatened by environmental contaminants.

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.

Monitoring Importance:

Yukon-Charley Rivers National Preserve (YUCH) was created by the Alaska National Interest Lands Conservation Act in 1980 in part because of its population of nesting Peregrine Falcons (Falco peregrinus anatum), making them a high priority focal species for monitoring. Focal raptor species are also monitored in the other network parks (Golden Eagles in Denali and Bald Eagles in Wrangell-St. Elias).

Besides Yukon-Charley Rivers enabling legislation, it makes ecological sense to monitor this species because Peregrines are a top trophic level predator that respond quickly to changes in the environment. They are also highly sensitive to environmental contaminants and habitat alteration. Moreover, the Peregrine population of the Upper Yukon River corridor is one of the densest in North America. They have been surveyed each year since 1975 and have a legacy as being one of the longest and most thoroughly studied populations of Peregrine Falcons in the world.

Monitoring Objectives:

1. Determine annual levels of nesting territory occupancy, nesting success, and overall population productivity.

2. Determine variation in nesting territory occupancy, nesting success, and productivity during the last decade.

3. Describe historic levels of environmental contaminants and eggshell thickness. Determine levels of organochlorine pesticides, mercury, and eggshell thickness every five years.

4. Measure changes in habitat on the breeding range.