Title

Comparison of Food Habits of the Northern Saw-Whet Owl (Aegolius acadicus) and the Western Screech-Owl (Otus kennicottii) in Southwestern Idaho

Document Type

NCA Publications/Misc

Publication Date

1-1-1997

Journal Title/Publication Source

Proceedings of the 2nd Owl Symposium

Page Numbers

339-346

Abstract

I compared the breeding-season diets of Northern Saw-whet Owls (Aegolius acadicus) and Western Screech-owls (Otus kennicottii). Prey items were obtained from regurgitated pellets collected from saw-whet owl and screech-owl nests found in nest boxes in the Snake RIver Birds of Prey National Conservation Area in southwestern Idaho. A total of 2,250 prey items of saw-whet owls and 702 prey items of screech-owls were identified. Saw-whet owl diet was anayzed for the years 1990-1993; screech-owl diet was analyzed for 1992 only. The most frequently found prey items in the saw-whet owls diet were: Peromyscus, Mus, Microtus and Reithrodontomys; there were no significant differences among years. When saw-whet owl prey frequency data were pooled across years and compared to the 1992 screech-owl data. Significant differences in diet were found. However, a comparison of the 1992 saw-whet prey frequency data with the screech-owl data showed no significant differences in diet were found. However, a comparison of the 1992 saw-whet owl prey biomass was analyzed, and again there were no significant differences. Microtus, followed by Mus, accounted for the largest proportion of prey biomass (by percent) in the diets of saw-whet owls for all years. When saw-whet owl prey biomass data were pooled across years and compared to the 1992 screech-owl prey biomass, significant differences in the diet were found. The 1992 saw-whet biomass compared to the 1992 screen-owl prey biomass also was significantly different. Saw-whet owl prey biomass fell manily between 11 and 55 grams; screech-owl prey biomass was more evenly distributed across the weight classes (0.5 grams- 400 grams).

Comments

Biology and conservation of owls of the northern hemisphere; second international symposium. February 5-9, 1997. Winnipeg, Manitoba, Canada. GTR NC-190. U.S. Department of Agriculture. Forest Service. North Central Forest Experiment Station, St. Paul, MN. https://www.nrs.fs.fed.us/pubs/

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Comparison of Food Habits of the Northern Saw-Whet Owl (Aegolius acadicus) and the Western Screech-Owl (Otus kennicottii) in Southwestern Idaho

I compared the breeding-season diets of Northern Saw-whet Owls (Aegolius acadicus) and Western Screech-owls (Otus kennicottii). Prey items were obtained from regurgitated pellets collected from saw-whet owl and screech-owl nests found in nest boxes in the Snake RIver Birds of Prey National Conservation Area in southwestern Idaho. A total of 2,250 prey items of saw-whet owls and 702 prey items of screech-owls were identified. Saw-whet owl diet was anayzed for the years 1990-1993; screech-owl diet was analyzed for 1992 only. The most frequently found prey items in the saw-whet owls diet were: Peromyscus, Mus, Microtus and Reithrodontomys; there were no significant differences among years. When saw-whet owl prey frequency data were pooled across years and compared to the 1992 screech-owl data. Significant differences in diet were found. However, a comparison of the 1992 saw-whet prey frequency data with the screech-owl data showed no significant differences in diet were found. However, a comparison of the 1992 saw-whet owl prey biomass was analyzed, and again there were no significant differences. Microtus, followed by Mus, accounted for the largest proportion of prey biomass (by percent) in the diets of saw-whet owls for all years. When saw-whet owl prey biomass data were pooled across years and compared to the 1992 screech-owl prey biomass, significant differences in the diet were found. The 1992 saw-whet biomass compared to the 1992 screen-owl prey biomass also was significantly different. Saw-whet owl prey biomass fell manily between 11 and 55 grams; screech-owl prey biomass was more evenly distributed across the weight classes (0.5 grams- 400 grams).