Prey Selection and Bioenergetics of Captive Screech Owls

Abstract

Screech owls appeared to select meadow voles {Microtus pennsylvanicus) as a primary food source, although deer mice (Peromyscus maniculatus) were apparently equally abundant and vulnerable. This feeding behavior resulted in a larger energy reward. A mean ingestion rate of 0.37 kcal/g live wt/day was derived from average values of 29-3 g live wt/day for Microtus as prey and only 11.3 g live wt/day for Peromyscus. Assimilation energy (ingestion-pellets-feces) was 0.28 kcal/g live wt/day; the mean assimilation efficiency (ingested energy-pellet energy-fecal energy/ingested energy x 100) was 76%. These findings support the hypothesis that a large energy reward is a prime factor in prey selection.