The Red—tailed Hawk population on a 60—mile2(156—km2) area in central Alberta was studied during 1965—68. This migratory population was present from early April to September each year. Breeding red—tails occupied open and forested habitats with equal facility, taking prey species from all cover types associated with nesting sites. Mammals, chiefly Richardson's ground squirrels and snowshoe hares, comprised 66% of total prey biomass taken by red—tails; waterfowl comprised 18%. Representation of meadow voles in the red—tail diet reflected annual variations in vole densities, but there was no consistent relationship between snowshoe hare and Ruffed Grouse densities and their utilization by red—tails. Numbers of adult red—tails resident on the study area varied little from year to year, and nesting success was not directly related to changes in cyclic hare and grouse populations. Red—tails took between 1.9 and 7.0% of the adult hares, and 0.3—0.8% of the juveniles on the study area during mid—April through August, 1966—68. Estimates of red—tail predation on Ruffed Grouse over this same period were 1.4 to 5.1% of adults, and 0.9 to 2.2% of juveniles. Calculated losses of Richardson's Ground squirrels to Red—tailed Hawks during 1967 and 1968 ranged from 22 to 60% in three populations. Losses of adults were especially high, and may have exceeded 90% in one instance. Adult male ground squirrels were significantly more vulnerable than adult females.