American peregrine falcon monitoring along the Upper Yukon River, Alaska, 2011

Ambrose, Skip; Florian, Chris

American Peregrine Falcons (Falco peregrinus anatum) nesting along the upper Yukon River, Alaska, have been monitored almost continuously since the late 1960s. This and other populations in North America declined drastically due to the use of persistent organochlorine pesticides which began in 1947. This interior Alaska population reached its lowest level in the mid-1970s, began to increase in 1978 (following restrictions on the use of DDT in the United States in 1972), and continued to increase through 2008. In 1999, the American Peregrine Falcon was removed from the list of Threatened and Endangered Wildlife (USFWS 1999). This local population along the upper Yukon River has been monitored almost continuously since the late-1960s. In 1982, the area was identified as an index study area in the Peregrine Falcon Recovery Plan, Alaska Population (USFWS 1982). In 2003, the area was identified as an index study area in interior Alaska for long-term, post-delisting monitoring (USFWS 2003). A monitoring protocol was developed in 2004 (Ambrose et al. 2005). In 2011, 265 kilometers of the upper Yukon River were surveyed. Fifty-four territories were occupied by American Peregrine Falcons (53 pairs and 1 single adult). Thirty-seven of 53 pairs (69.8%) were successful, and produced 75 nestlings. Productivity was 1.42 nestlings per total pair and 2.03 nestlings per successful pair (≥ 1 nestling observed). Between 1975 and 2008, the number of pairs and number of nestlings increased steadily. In recent years, the number of pairs of American Peregrine Falcons along the upper Yukon River appears to be stabilizing, remaining at 53 pairs for the last three years (2009-2011). The percent pairs successful, although still variable, also shows signs of stabilizing, remaining between about 60-70% since 2005. The number of nestlings per total pair and nestlings per successful pair has been gradually declining since the late 1970s and appears to be stabilizing, although with a great deal annual variation (likely due to variable weather in the study area). Historical data on a healthy population of American Peregrine Falcons are not available. Intensive surveys did not take place prior to declines caused by the use of persistent organochlorine pesticides. This local population of American Peregrine Falcons along the upper Yukon River has been studied intensively since the late 1960s, and now appears to be nearing full recovery and stabilizing. Continued intensive annual monitoring is necessary to fully understand the natural variation of a “healthy” peregrine falcon population, which will allow detection of population changes beyond normal annual variation.

American peregrine falcon monitoring along the Upper Yukon River, Alaska, 2011

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