Ornis Hungarica. vol.26(2). (2018) p.134-142.
Mackenzie River Peregrine Falcon Surveys 1966–2018
The author with assistants monitored the breeding distribution of Peregrine Falcons (Falco peregrinus) along the length of the Mackenzie River, Northwest Territories, Canada from 1966 to 2018. This river traverses a thousand miles (1600 km) of the western Canadian Arctic from Great Slave Lake to the Beaufort Sea and roughly parallels the eastern slope of the Mackenzie Mountain cordillera between latitudes 61 degrees N and 68 degrees N. All potential nest sites have been checked on each survey and counts of nest sites occupied (at least one bird seen) decreased from the count of 12 sites in 1966 to the lowest count of 7 in 1972. In 1990 the count was 37 and up to 2018 the highest count was 75 in 2010. A count of nest sites successfully producing young was variable with a low of 5 in 1972 to a high of 58 in 2011.
Production of young averaged 2.43/successful site from 1990 until 2018 (excluding 2012). Production of young averaged 1.4/ occupied site over this period. Recent increases in availability of passerine prey because of widespread fires in the last decades are felt to be the latest phenomena affecting these birds (pers.obs.) Prey utilized by Peregrines was studied over a period of four years and passerines composed 20% of their diet. Two species Lesser Scaup (Athya affinis) and Lesser Yellowlegs (Tringa flavipes) formed 25% of their diet.