Breeding-season diet of northern saw-whet owls in southwestern Idaho

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Northern Saw-whet Owl (Aegolius acadicus) is a common inhabitant of forested lands from central Canada south to the central United States. Despite its wide range, very little is known of its breeding biology. Catling (1972) noted that food habits data from the breeding season are “very meagre.” Indeed, we know of only one large sample of Northern Saw-whet Owl food habits from the breeding season. Eight Northern Saw-whet Owl nests (1 in 1986 and 7 in 1987) were found in the Snake River Birds of Prey Area (BOPA) in southwestern Idaho. Unlike typical Northern Saw-whet Owl nesting habitat, the vegetation of the BOPA is shrub-steppe desert dominated by big sagebrush (Artemisia tridentata). Trees are scarce and are confined to watercourses and farm settlements. All Northern Saw-whet Owl nests were in nest boxes, either in native riparian willows (Salix sp.) or in groves of exotic Russian olives (Elaeagnus angustifolia) and black locusts (Robinia pseudoacacia). Three of the nesting females in 1987 mated with the same male. We present data on diet composition and prey size of these owls during the breeding eason. We also compare our data with those from the recent studies of Boula (1982), Grove (1985), and Cannings (1987) to characterize the trophic niche of Northern Saw-whet Owls, based on data available from the Pacific Northwest.

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Reference Code: A88MAR02IDUS

Full Citation: Marks, J. S., and J. H. Doremus. 1988. Breeding-season diet of northern saw-whet owls in southwestern Idaho. Wilson Bulletin 100(4): 690-694.

Location: ANIMAL EF: BIRDS